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130-436: A sexually transmitted infection ( STI ), also referred to as a sexually transmitted disease ( STD ) and the older term venereal disease ( VD ), is an infection that is spread by sexual activity , especially vaginal intercourse , anal sex , oral sex , or sometimes manual sex . STIs often do not initially cause symptoms, which results in a risk of transmitting them on to others. The term sexually transmitted infection

260-456: A prion . The benefits of identification, however, are often greatly outweighed by the cost, as often there is no specific treatment, the cause is obvious, or the outcome of an infection is likely to be benign . The diagnosis is aided by the presenting symptoms in any individual with an infectious disease, yet it usually needs additional diagnostic techniques to confirm the suspicion. Some signs are specifically characteristic and indicative of

390-422: A runny nose . In certain cases, infectious diseases may be asymptomatic for much or even all of their course in a given host. In the latter case, the disease may only be defined as a "disease" (which by definition means an illness) in hosts who secondarily become ill after contact with an asymptomatic carrier . An infection is not synonymous with an infectious disease, as some infections do not cause illness in

520-441: A "rebound" effect following overuse of decongestants may produce nasal or sinus drainage problems and circumstances that promote infection. During cold, dry seasons, the mucus lining nasal passages tends to dry out, meaning that mucous membranes must work harder, producing more mucus to keep the cavity lined. As a result, the nasal cavity can fill up with mucus. At the same time, when air is exhaled, water vapor in breath condenses as

650-420: A charge selective diffusion barrier, thus significantly affecting the transportation of agents. Among particles with various surface zeta potentials , cationic particles tend to have a low depth of penetration, neutral ones possess medium penetration, and anionic ones have the largest penetration depth. Furthermore, the effect of charge selectivity changes when the status of the mucus varies, i.e., native mucus has

780-425: A colonization is often only a matter of circumstance. Non-pathogenic organisms can become pathogenic given specific conditions, and even the most virulent organism requires certain circumstances to cause a compromising infection. Some colonizing bacteria, such as Corynebacteria sp. and Viridans streptococci , prevent the adhesion and colonization of pathogenic bacteria and thus have a symbiotic relationship with

910-616: A condom is effective in limiting exposure, some disease transmission may occur even with a condom. Both partners can get tested for STIs before initiating sexual contact, or before resuming contact if a partner engaged in contact with someone else. Many infections are not detectable immediately after exposure, so enough time must be allowed between possible exposures and testing for the tests to be accurate. Certain STIs, particularly certain persistent viruses like HPV, may be impossible to detect. Some treatment facilities use in-home test kits and have

1040-469: A disease and are called pathognomonic signs; but these are rare. Not all infections are symptomatic. In children the presence of cyanosis , rapid breathing, poor peripheral perfusion, or a petechial rash increases the risk of a serious infection by greater than 5 fold. Other important indicators include parental concern, clinical instinct, and temperature greater than 40 °C. Many diagnostic approaches depend on microbiological culture to isolate

1170-938: A disease may result from even light contact from fluid carriers like venereal fluids onto a mucous membrane. Some STIs such as HIV can be transmitted from mother to child either during pregnancy or breastfeeding. Healthcare professionals suggest safer sex , such as the use of condoms , as a reliable way of decreasing the risk of contracting sexually transmitted infections during sexual activity, but safer sex cannot be considered to provide complete protection from an STI. The transfer of and exposure to bodily fluids, such as blood transfusions and other blood products, sharing injection needles , needle-stick injuries (when medical staff are inadvertently jabbed or pricked with needles during medical procedures), sharing tattoo needles, and childbirth are other avenues of transmission. These different means put certain groups, such as medical workers, and haemophiliacs and drug users, particularly at risk. It

1300-399: A disease. This amplification of nucleic acid in infected tissue offers an opportunity to detect the infectious agent by using PCR. Third, the essential tools for directing PCR, primers , are derived from the genomes of infectious agents, and with time those genomes will be known if they are not already. Thus, the technological ability to detect any infectious agent rapidly and specifically

1430-462: A district in Paris formerly known as "Le Clapiers". This is where the prostitutes were to be found at that time. Prior to the invention of modern medicines, sexually transmitted infections were generally incurable, and treatment was limited to treating the symptoms of the infection. The first voluntary hospital for STIs was founded in 1746 at London Lock Hospital . Treatment was not always voluntary: in

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1560-400: A higher risk of HIV infection. There is evidence that vaginal dapivirine probably reduces HIV in women who have sex with men, other types of vaginal microbicides have not demonstrated effectiveness for HIV or STIs. There is little evidence that school-based interventions such as sexual and reproductive health education programmes on contraceptive choices and condoms are effective on improving

1690-423: A hospital stay. Lastly, a community-acquired infection is one in which the infection is acquired from a whole community. One manner of proving that a given disease is infectious, is to satisfy Koch's postulates (first proposed by Robert Koch ), which require that first, the infectious agent be identifiable only in patients who have the disease, and not in healthy controls, and second, that patients who contract

1820-531: A host with depressed resistance ( immunodeficiency ) or if they have unusual access to the inside of the body (for example, via trauma ). Opportunistic infection may be caused by microbes ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract , and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridioides difficile colitis ) or from

1950-502: A host. As bacterial and viral infections can both cause the same kinds of symptoms, it can be difficult to distinguish which is the cause of a specific infection. Distinguishing the two is important, since viral infections cannot be cured by antibiotics whereas bacterial infections can. There is a general chain of events that applies to infections, sometimes called the chain of infection or transmission chain . The chain of events involves several steps – which include

2080-434: A link between virulence and transmissibility. Diagnosis of infectious disease sometimes involves identifying an infectious agent either directly or indirectly. In practice most minor infectious diseases such as warts , cutaneous abscesses , respiratory system infections and diarrheal diseases are diagnosed by their clinical presentation and treated without knowledge of the specific causative agent. Conclusions about

2210-430: A negative side chain when the pH value is above 3.9, while a neutrally charged side chain will be introduced as pH value drops below 3.9. Thus, the number of negative charges in mucus is influenced by the pH value of surrounding environment. That is, the polyelectrolyte effect of mucus is largely affected by the pH value of solution due to the charge variation of acidic amino acid residues on the mucin backbone. For instance,

2340-518: A number of basic dyes due to the electrostatic attraction between negatively charged cellular molecules and the positive charge on the dye. A cell is normally transparent under a microscope, and using a stain increases the contrast of a cell with its background. Staining a cell with a dye such as Giemsa stain or crystal violet allows a microscopist to describe its size, shape, internal and external components and its associations with other cells. The response of bacteria to different staining procedures

2470-441: A number of reasons: Early identification and treatment results in less chance to spread disease, and for some conditions may improve the outcomes of treatment. There is often a window period after initial infection during which an STI test will be negative. During this period, the infection may be transmissible. The duration of this period varies depending on the infection and the test. Diagnosis may also be delayed by reluctance of

2600-404: A particular pathogen at all (no matter how little) but also is often used in a sense implying a clinically apparent infection (in other words, a case of infectious disease). This fact occasionally creates some ambiguity or prompts some usage discussion; to get around this it is common for health professionals to speak of colonization (rather than infection ) when they mean that some of

2730-493: A pathogen from the appropriate clinical specimen. In a microbial culture, a growth medium is provided for a specific agent. A sample taken from potentially diseased tissue or fluid is then tested for the presence of an infectious agent able to grow within that medium. Many pathogenic bacteria are easily grown on nutrient agar , a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into

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2860-429: A pathogen. A fluorescence microscope is then used to detect fluorescently labeled antibodies bound to internalized antigens within clinical samples or cultured cells. This technique is especially useful in the diagnosis of viral diseases, where the light microscope is incapable of identifying a virus directly. Other microscopic procedures may also aid in identifying infectious agents. Almost all cells readily stain with

2990-432: A patient's blood or other body fluids for antigens or antibodies that indicate presence of a specific pathogen that the doctor suspects. Other techniques (such as X-rays , CAT scans , PET scans or NMR ) are used to produce images of internal abnormalities resulting from the growth of an infectious agent. The images are useful in detection of, for example, a bone abscess or a spongiform encephalopathy produced by

3120-470: A persistent infection by infecting different cells of the body. Some viruses once acquired never leave the body. A typical example is the herpes virus, which tends to hide in nerves and become reactivated when specific circumstances arise. Persistent infections cause millions of deaths globally each year. Chronic infections by parasites account for a high morbidity and mortality in many underdeveloped countries. For infecting organisms to survive and repeat

3250-415: A pregnant woman may be passed on to the infant before or after birth. Sexually transmitted infections include: Twenty-seven different viruses have been identified in semen. Information on whether or not transmission occurs or whether the viruses cause disease is uncertain. Some of these microbes are known to be sexually transmitted. Many STIs are (more easily) transmitted through the mucous membranes of

3380-414: A public perception during the 1960s and 1970s that they have ceased to be a serious medical threat. During this period, the importance of contact tracing in treating STIs was recognized. By tracing the sexual partners of infected individuals, testing them for infection, treating the infected and tracing their contacts, in turn, STI clinics could effectively suppress infections in the general population. In

3510-403: A result of an infectious disease with immunosuppressive activity (such as with measles , malaria or HIV disease ). Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host. While a primary infection can practically be viewed as the root cause of an individual's current health problem, a secondary infection

3640-471: A result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however, many serious diseases are caused by organisms acquired from the environment or that infect non-human hosts. Opportunistic pathogens can cause an infectious disease in

3770-411: A severe illness affecting the brain, remain undiagnosed, despite extensive testing using the standard of care ( microbiological culture ) and state-of-the-art clinical laboratory methods. Metagenomic sequencing-based diagnostic tests are currently being developed for clinical use and show promise as a sensitive, specific, and rapid way to diagnose infection using a single all-encompassing test. This test

3900-417: A specific identification of an infectious agent only when such identification can aid in the treatment or prevention of the disease, or to advance knowledge of the course of an illness prior to the development of effective therapeutic or preventative measures. For example, in the early 1980s, prior to the appearance of AZT for the treatment of AIDS , the course of the disease was closely followed by monitoring

4030-422: A threefold higher potential to limit agent penetration than purified mucus. Mucus is also produced by a number of other animals. All fish are covered in mucus secreted from glands all over their bodies. Invertebrates such as snails and slugs secrete mucus called snail slime to enable movement, and to prevent their bodies from drying out. Their reproductive systems also make use of mucus for example in

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4160-432: A visible mound on the surface of the plate called a colony , which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its strain ), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit

4290-423: A woman's fertile time at the mid-point of the cycle. Awareness of the woman's fertile time allows a couple to time intercourse to improve the odds of pregnancy. It is also proposed as a method to avoid pregnancy. In general, nasal mucus is clear and thin, serving to filter air during inhalation. During times of infection, mucus can change color to yellow or green either as a result of trapped bacteria or due to

4420-509: Is a sequela or complication of that root cause. For example, an infection due to a burn or penetrating trauma (the root cause) is a secondary infection. Primary pathogens often cause primary infection and often cause secondary infection. Usually, opportunistic infections are viewed as secondary infections (because immunodeficiency or injury was the predisposing factor). Other types of infection consist of mixed, iatrogenic , nosocomial , and community-acquired infection. A mixed infection

4550-428: Is a polymeric protein secreted from submucosal glands and some goblet cells, and this is in the form of strands. In the airways—the trachea , bronchi , and bronchioles —the lining of mucus is produced by specialized airway epithelial cells called goblet cells , and submucosal glands . Small particles such as dust, particulate pollutants , and allergens , as well as infectious agents and bacteria are caught in

4680-507: Is active but does not produce noticeable symptoms may be called inapparent, silent, subclinical , or occult . An infection that is inactive or dormant is called a latent infection . An example of a latent bacterial infection is latent tuberculosis . Some viral infections can also be latent, examples of latent viral infections are any of those from the Herpesviridae family. The word infection can denote any presence of

4810-452: Is advised to assure maximal protection. The development of vaccines to protect against gonorrhea is ongoing. Condoms and female condoms only provide protection when used properly as a barrier, and only to and from the area that they cover. Uncovered areas are still susceptible to many STIs. In the case of HIV, sexual transmission routes almost always involve the penis, as HIV cannot spread through unbroken skin; therefore, properly shielding

4940-423: Is also produced by some microorganisms . In the human respiratory system , mucus is part of the airway surface liquid (ASL), also known as epithelial lining fluid (ELF), that lines most of the respiratory tract . The airway surface liquid consists of a sol layer termed the periciliary liquid layer and an overlying gel layer termed the mucus layer. The periciliary liquid layer is so named as it surrounds

5070-423: Is an infection that is caused by two or more pathogens. An example of this is appendicitis , which is caused by Bacteroides fragilis and Escherichia coli . The second is an iatrogenic infection. This type of infection is one that is transmitted from a health care worker to a patient. A nosocomial infection is also one that occurs in a health care setting. Nosocomial infections are those that are acquired during

5200-422: Is an initial site of infection from which organisms travel via the bloodstream to another area of the body. Among the many varieties of microorganisms , relatively few cause disease in otherwise healthy individuals. Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect. The appearance and severity of disease resulting from any pathogen depend upon

5330-510: Is currently available. The only remaining blockades to the use of PCR as a standard tool of diagnosis are in its cost and application, neither of which is insurmountable. The diagnosis of a few diseases will not benefit from the development of PCR methods, such as some of the clostridial diseases ( tetanus and botulism ). These diseases are fundamentally biological poisonings by relatively small numbers of infectious bacteria that produce extremely potent neurotoxins . A significant proliferation of

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5460-474: Is directed at a person's risk, the situations in which risk occurs, and the use of personalized goal-setting strategies. The most effective way to prevent sexual transmission of STIs is to avoid contact of body parts or fluids which can lead to transfer with an infected partner. Not all sexual activities involve contact: cybersex , phone sex or masturbation from a distance are methods of avoiding contact. Proper use of condoms reduces contact and risk. Although

5590-521: Is generally preferred over sexually transmitted disease or venereal disease , as it includes cases with no symptomatic disease . Symptoms and signs of STIs may include vaginal discharge , penile discharge , ulcers on or around the genitals , and pelvic pain . Some STIs can cause infertility . Bacterial STIs include chlamydia , gonorrhea , and syphilis . Viral STIs include genital warts , genital herpes , and HIV/AIDS . Parasitic STIs include trichomoniasis . Most STIs are treatable and curable, of

5720-442: Is generally symptom-based; often it is sufficient to allow the immune system to fight off the virus over time. Obstructive lung diseases often result from impaired mucociliary clearance that can be associated with mucus hypersecretion, and these are sometimes referred to as mucoobstructive lung diseases . Techniques of airway clearance therapy can help to clear secretions, maintain respiratory health, and prevent inflammation in

5850-503: Is injured. All multicellular organisms are colonized to some degree by extrinsic organisms, and the vast majority of these exist in either a mutualistic or commensal relationship with the host. An example of the former is the anaerobic bacteria species, which colonizes the mammalian colon , and an example of the latter are the various species of staphylococcus that exist on human skin . Neither of these colonizations are considered infections. The difference between an infection and

5980-403: Is known as mucus hypersecretion . Chronic mucus hypersecretion results in the chronic productive cough of chronic bronchitis , and is generally synonymous with this. Excessive mucus can narrow the airways, limit airflow, and accelerate a decline in lung function. In the human digestive system , mucus is used as a lubricant for materials that must pass over membranes, e.g., food passing down

6110-550: Is most effective if provided in a nonjudgmental and empathetic manner appropriate to the person's culture, language, gender, sexual orientation, age, and developmental level. Prevention counseling for STIs is usually offered to all sexually active adolescents and to all adults who have received a diagnosis, have had an STI in the past year, or have multiple sex partners . Vaccines are available that protect against some viral STIs, such as hepatitis A , hepatitis B , and some types of HPV . Vaccination before initiation of sexual contact

6240-467: Is not an enzyme and has no metabolic function. Serological methods are highly sensitive, specific and often extremely rapid tests used to identify microorganisms. These tests are based upon the ability of an antibody to bind specifically to an antigen. The antigen, usually a protein or carbohydrate made by an infectious agent, is bound by the antibody. This binding then sets off a chain of events that can be visibly obvious in various ways, dependent upon

6370-476: Is possible to be an asymptomatic carrier of sexually transmitted infections. In particular, sexually transmitted infections in women often cause the serious condition of pelvic inflammatory disease. Testing may be for a single infection, or consist of a number of tests for a range of STIs, including tests for syphilis , trichomonas , gonorrhea, chlamydia , herpes , hepatitis , and HIV . No procedure tests for all infectious agents. STI tests may be used for

6500-425: Is referred to as infectious diseases . Infections are caused by infectious agents ( pathogens ) including: The signs and symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue , loss of appetite, weight loss, fevers , night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes , coughing , or

6630-404: Is referred to as colonization. Most humans are not easily infected. Those with compromised or weakened immune systems have an increased susceptibility to chronic or persistent infections. Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections . Entrance to the host at host–pathogen interface , generally occurs through the mucosa in orifices like

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6760-501: Is similar to current PCR tests; however, an untargeted whole genome amplification is used rather than primers for a specific infectious agent. This amplification step is followed by next-generation sequencing or third-generation sequencing , alignment comparisons , and taxonomic classification using large databases of thousands of pathogen and commensal reference genomes . Simultaneously, antimicrobial resistance genes within pathogen and plasmid genomes are sequenced and aligned to

6890-439: Is that microbial colonization is very common even in environments that humans think of as being nearly sterile . Because it is normal to have bacterial colonization, it is difficult to know which chronic wounds can be classified as infected and how much risk of progression exists. Despite the huge number of wounds seen in clinical practice, there are limited quality data for evaluated symptoms and signs. A review of chronic wounds in

7020-409: Is the clinical practice of treating the sex partners of index cases by providing prescriptions or medications to the patient to take to their partner without the health care provider first examining the partner. In term of preventing reinfection in sexually transmitted infection, treatment with both patient and the sexual partner of patient resulted in more successful than treatment of the patient without

7150-458: Is the fundamental characteristic of cystic fibrosis , an inherited disease caused by mutations in the CFTR gene, which encodes a chloride channel . This defect leads to the altered electrolyte composition of mucus, which triggers its hyperabsorption and dehydration. Such low-volume, viscous, acidic mucus has a reduced antimicrobial function, which facilitates bacterial colonisation. The thinning of

7280-870: Is the invasion of tissues by pathogens , their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease , also known as a transmissible disease or communicable disease , is an illness resulting from an infection. Infections can be caused by a wide range of pathogens , most prominently bacteria and viruses . Hosts can fight infections using their immune systems . Mammalian hosts react to infections with an innate response, often involving inflammation , followed by an adaptive response. Specific medications used to treat infections include antibiotics , antivirals , antifungals , antiprotozoals , and antihelminthics . Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections

7410-561: Is then known as phlegm which may be coughed up as sputum to clear the airway. Increased mucus production in the upper respiratory tract is a symptom of many common ailments, such as the common cold , and influenza . Nasal mucus may be removed by blowing the nose or by using nasal irrigation . Excess nasal mucus, as with a cold or allergies , due to vascular engorgement associated with vasodilation and increased capillary permeability caused by histamines , may be treated cautiously with decongestant medications. Thickening of mucus as

7540-421: Is used for each act of intercourse, as multiple usages increase the chance of breakage, defeating the effectiveness as a barrier. In the case of female condoms, the device consists of two rings, one in each terminal portion. The larger ring should fit snugly over the cervix and the smaller ring remains outside the vagina, covering the vulva. This system provides some protection of the external genitalia. The cap

7670-588: Is used in the taxonomic classification of microbes as well. Two methods, the Gram stain and the acid-fast stain, are the standard approaches used to classify bacteria and to diagnosis of disease. The Gram stain identifies the bacterial groups Bacillota and Actinomycetota , both of which contain many significant human pathogens. The acid-fast staining procedure identifies the Actinomycetota genera Mycobacterium and Nocardia . Biochemical tests used in

7800-666: The Ebers Papyrus ( c.  1550 BCE ) and the Hebrew Bible / Old Testament (8th/7th C. BCE). Not all STIs are symptomatic , and symptoms may not appear immediately after infection. In some instances a disease can be carried with no symptoms, which leaves a greater risk of passing the disease on to others. Depending on the disease, some untreated STIs can lead to infertility , chronic pain or death. The presence of an STI in prepubescent children may indicate sexual abuse . A sexually transmitted infection present in

7930-605: The Journal of the American Medical Association 's "Rational Clinical Examination Series" quantified the importance of increased pain as an indicator of infection. The review showed that the most useful finding is an increase in the level of pain [likelihood ratio (LR) range, 11–20] makes infection much more likely, but the absence of pain (negative likelihood ratio range, 0.64–0.88) does not rule out infection (summary LR 0.64–0.88). Disease can arise if

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8060-413: The cilia and lies on top of the surface epithelium. The periciliary liquid layer surrounding the cilia consists of a gel meshwork of cell-tethered mucins and polysaccharides. The mucus blanket aids in the protection of the lungs by trapping foreign particles before they can enter them, in particular through the nose during normal breathing. Mucus is made up of a fluid component of around 95% water,

8190-414: The esophagus . Mucus is extremely important in the gastrointestinal tract . It forms an essential layer in the colon and in the small intestine that helps reduce intestinal inflammation by decreasing bacterial interaction with intestinal epithelial cells. The layer of mucus of the gastric mucosa lining the stomach is vital to protect the stomach lining from the highly acidic environment within it. In

8320-406: The mucin secretions from the goblet cells, and the submucosal glands (2–3% glycoproteins), proteoglycans (0.1–0.5%), lipids (0.3–0.5%), proteins, and DNA. The major mucins secreted – MUC5AC and MUC5B - are large polymers that give the mucus its rheologic or viscoelastic properties. MUC5AC is the main gel-forming mucin secreted by goblet cells, in the form of threads and thin sheets. MUC5B

8450-468: The oral cavity , nose, eyes, genitalia, anus, or the microbe can enter through open wounds. While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids. Wound colonization refers to non-replicating microorganisms within the wound, while in infected wounds, replicating organisms exist and tissue

8580-494: The penis , vulva , rectum , urinary tract and (less often—depending on type of infection) the mouth , throat , respiratory tract and eyes . The visible membrane covering the head of the penis is a mucous membrane, though it produces no mucus (similar to the lips of the mouth). Mucous membranes differ from skin in that they allow certain pathogens into the body. The amount of contact with infective sources which causes infection varies with each pathogen but in all cases,

8710-447: The polymerase chain reaction (PCR) method will become nearly ubiquitous gold standards of diagnostics of the near future, for several reasons. First, the catalog of infectious agents has grown to the point that virtually all of the significant infectious agents of the human population have been identified. Second, an infectious agent must grow within the human body to cause disease; essentially it must amplify its own nucleic acids to cause

8840-403: The "strep test", they can be inexpensive. Complex serological techniques have been developed into what are known as immunoassays . Immunoassays can use the basic antibody – antigen binding as the basis to produce an electro-magnetic or particle radiation signal, which can be detected by some form of instrumentation. Signal of unknowns can be compared to that of standards allowing quantitation of

8970-449: The 1980s, first genital herpes and then AIDS emerged into the public consciousness as sexually transmitted infections that could not be cured by modern medicine. AIDS, in particular, has a long asymptomatic period—during which time HIV (the human immunodeficiency virus, which causes AIDS) can replicate and the disease can be transmitted to others—followed by a symptomatic period, which leads rapidly to death unless treated. HIV/AIDS entered

9100-681: The Americas and Europe. Approximately two billion people worldwide have been infected with the hepatitis B virus. The first well-recorded European outbreak of what is now known as syphilis occurred in 1494 when it broke out among French troops besieging Naples in the Italian War of 1494–98 . The disease may have originated from the Columbian Exchange . From Naples, the disease swept across Europe , killing more than five million people. As Jared Diamond describes it, "[W]hen syphilis

9230-482: The United States from Haiti in about 1969. Recognition that AIDS threatened a global pandemic led to public information campaigns and the development of treatments that allow AIDS to be managed by suppressing the replication of HIV for as long as possible. Contact tracing continues to be an important measure, even when diseases are incurable, as it helps to contain infection. Infection An infection

9360-581: The United States there were 19 million new cases of sexually transmitted infections in 2010. In 2010, 19 million new cases of sexually transmitted infections occurred in women in the United States. A 2008 CDC study found that 25–40% of U.S. teenage girls has a sexually transmitted infection. Out of a population of almost 295,270,000 people there were 110 million new and existing cases of eight sexually transmitted infections. Over 400,000 sexually transmitted infections were reported in England in 2017, about

9490-435: The ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen. However, a host's immune system can also cause damage to the host itself in an attempt to control the infection. Clinicians, therefore, classify infectious microorganisms or microbes according to the status of host defenses – either as primary pathogens or as opportunistic pathogens . Primary pathogens cause disease as

9620-435: The airways. A unique umbilical cord lining epithelial stem cell expresses MUC1 , termed (CLEC-muc). This has been shown to have good potential in the regeneration of the cornea . Mucus is able to absorb water or dehydrate through pH variations. The swelling capacity of mucus stems from the bottlebrush structure of mucin within which hydrophilic segments provide a large surface area for water absorption. Moreover,

9750-458: The basis of a biochemical diagnosis of an infectious disease. For example, humans can make neither RNA replicases nor reverse transcriptase , and the presence of these enzymes are characteristic., of specific types of viral infections. The ability of the viral protein hemagglutinin to bind red blood cells together into a detectable matrix may also be characterized as a biochemical test for viral infection, although strictly speaking hemagglutinin

9880-411: The body's reaction to viral infection. For example, Staphylococcus aureus infection may turn the mucus yellow. The green color of mucus comes from the heme group in the iron-containing enzyme myeloperoxidase secreted by white blood cells as a cytotoxic defense during a respiratory burst . In the case of bacterial infection, the bacterium becomes trapped in already-clogged sinuses , breeding in

10010-411: The case of a viral infection such as cold or flu , the first stage and also the last stage of the infection cause the production of a clear, thin mucus in the nose or back of the throat. As the body begins to react to the virus (generally one to three days), mucus thickens and may turn yellow or green. Viral infections cannot be treated with antibiotics, and are a major avenue for their misuse. Treatment

10140-463: The case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". Eukaryotic parasites may also be grown in culture as a means of identifying a particular agent. In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make

10270-476: The causative agent, Trypanosoma cruzi in a patient, which therefore makes it difficult to definitively make a diagnosis. In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi , an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of T. cruzi within its gut. Another principal tool in

10400-436: The cause of the disease are based upon the likelihood that a patient came in contact with a particular agent, the presence of a microbe in a community, and other epidemiological considerations. Given sufficient effort, all known infectious agents can be specifically identified. Diagnosis of infectious disease is nearly always initiated by medical history and physical examination. More detailed identification techniques involve

10530-759: The charged groups in the polyelectrolytes attract counter-ions with opposite charges, thereby leading to a solute concentration gradient. An osmotic pressure is introduced to equalize the concentration of solute throughout the system by driving water to flow from the low concentration areas to the high concentration areas. In short, the influx and outflux of water within mucus, managed by the polyelectrolyte effect, contribute to mucus' tunable swelling capacity. The ionic charges of mucin are mainly provided by acidic amino acids including aspartic acid ( pKa =3.9) and glutamic acid (pKa=4.2). The charges of acidic amino acids will change with environmental pH value due to acid dissociation and association. Aspartic acid, for example, has

10660-464: The charged residue on mucin is protonated at a normal pH value of the stomach, approximately pH 2. In this case, there is scarcely polyelectrolyte effect, thereby causing compact mucus with little swelling capacity. However, a kind of bacteria, Helicobacter pylori , is prone to producing base to elevate the pH value in stomach, leading to the deprotonation of aspartic acids and glutamic acids, i.e., from neutral to negative-charged. The negative charges in

10790-431: The composition of patient blood samples, even though the outcome would not offer the patient any further treatment options. In part, these studies on the appearance of HIV in specific communities permitted the advancement of hypotheses as to the route of transmission of the virus. By understanding how the disease was transmitted, resources could be targeted to the communities at greatest risk in campaigns aimed at reducing

10920-484: The culture of infectious agents isolated from a patient. Culture allows identification of infectious organisms by examining their microscopic features, by detecting the presence of substances produced by pathogens, and by directly identifying an organism by its genotype. Many infectious organisms are identified without culture and microscopy. This is especially true for viruses, which cannot grow in culture. For some suspected pathogens, doctors may conduct tests that examine

11050-400: The destruction of the virus. Instrumentation can be used to read extremely small signals created by secondary reactions linked to the antibody – antigen binding. Instrumentation can control sampling, reagent use, reaction times, signal detection, calculation of results, and data management to yield a cost-effective automated process for diagnosis of infectious disease. Technologies based upon

11180-428: The diagnosis of infectious disease is microscopy . Virtually all of the culture techniques discussed above rely, at some point, on microscopic examination for definitive identification of the infectious agent. Microscopy may be carried out with simple instruments, such as the compound light microscope , or with instruments as complex as an electron microscope . Samples obtained from patients may be viewed directly under

11310-445: The environment as a result of traumatic introduction (as in surgical wound infections or compound fractures ). An opportunistic disease requires impairment of host defenses, which may occur as a result of genetic defects (such as chronic granulomatous disease ), exposure to antimicrobial drugs or immunosuppressive chemicals (as might occur following poisoning or cancer chemotherapy ), exposure to ionizing radiation , or as

11440-426: The expression of symptoms is often atypical, making a clinical diagnosis based on presentation more difficult. Thirdly, diagnostic methods that rely on the detection of antibodies are more likely to fail. A rapid, sensitive, specific, and untargeted test for all known human pathogens that detects the presence of the organism's DNA rather than antibodies is therefore highly desirable. There is usually an indication for

11570-403: The growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of viruses : the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In

11700-484: The host's protective immune mechanisms are compromised and the organism inflicts damage on the host. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, Clostridium tetani releases a toxin that paralyzes muscles, and staphylococcus releases toxins that produce shock and sepsis . Not all infectious agents cause disease in all hosts. For example, less than 5% of individuals infected with polio develop disease. On

11830-598: The host, preventing infection and speeding wound healing . The variables involved in the outcome of a host becoming inoculated by a pathogen and the ultimate outcome include: As an example, several staphylococcal species remain harmless on the skin, but, when present in a normally sterile space, such as in the capsule of a joint or the peritoneum , multiply without resistance and cause harm. An interesting fact that gas chromatography–mass spectrometry , 16S ribosomal RNA analysis, omics , and other advanced technologies have made more apparent to humans in recent decades

11960-495: The human female reproductive system, cervical mucus prevents infection and provides lubrication during sexual intercourse. The consistency of cervical mucus varies depending on the stage of a woman's menstrual cycle. At ovulation cervical mucus is clear, runny, and conducive to sperm ; post-ovulation, mucus becomes thicker and is more likely to block sperm. Several fertility awareness methods rely on observation of cervical mucus, as one of three primary fertility signs, to identify

12090-532: The identification of infectious agents include the detection of metabolic or enzymatic products characteristic of a particular infectious agent. Since bacteria ferment carbohydrates in patterns characteristic of their genus and species , the detection of fermentation products is commonly used in bacterial identification. Acids , alcohols and gases are usually detected in these tests when bacteria are grown in selective liquid or solid media. The isolation of enzymes from infected tissue can also provide

12220-588: The infected person to seek a medical professional. One report indicated that people turn to the Internet rather than to a medical professional for information on STIs to a higher degree than for other sexual problems. Until the 1990s, STIs were commonly known as venereal diseases , an antiquated euphemism derived from the Latin venereus , being the adjectival form of Venus , the Roman goddess of love. However, in

12350-413: The infection cycle in other hosts, they (or their progeny) must leave an existing reservoir and cause infection elsewhere. Infection transmission can take place via many potential routes: The relationship between virulence versus transmissibility is complex; with studies have shown that there were no clear relationship between the two. There is still a small number of evidence that partially suggests

12480-425: The infectious agent also develop the disease. These postulates were first used in the discovery that Mycobacteria species cause tuberculosis . Mucus Amphibians , fish , snails , slugs , and some other invertebrates also produce external mucus from their epidermis as protection against pathogens, to help in movement, and to line fish gills . Plants produce a similar substance called mucilage that

12610-399: The infectious agent does not occur, this limits the ability of PCR to detect the presence of any bacteria. Given the wide range of bacterial, viral, fungal, protozoal, and helminthic pathogens that cause debilitating and life-threatening illnesses, the ability to quickly identify the cause of infection is important yet often challenging. For example, more than half of cases of encephalitis ,

12740-402: The infectious agent, reservoir, entering a susceptible host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place. Infection begins when an organism successfully enters the body, grows and multiplies. This

12870-458: The inhaled air and prevents tissues such as the nasal and airway epithelia from drying out. Mucus is produced continuously in the respiratory tract . Mucociliary action carries it down from the nasal passages and up from the rest of the tract to the pharynx, with most of it being swallowed subconsciously. Sometimes in times of respiratory illness or inflammation, mucus can become thickened with cell debris, bacteria, and inflammatory cells. It

13000-509: The leading causes of death in present-day Sub-Saharan Africa . HIV/AIDS is transmitted primarily via unprotected sexual intercourse. More than 1.1 million persons are living with HIV/AIDS in the United States , and it disproportionately impacts African Americans . Hepatitis B is also considered a sexually transmitted infection because it can be spread through sexual contact. The highest rates are found in Asia and Africa and lower rates are in

13130-425: The light microscope, and can often rapidly lead to identification. Microscopy is often also used in conjunction with biochemical staining techniques, and can be made exquisitely specific when used in combination with antibody based techniques. For example, the use of antibodies made artificially fluorescent (fluorescently labeled antibodies) can be directed to bind to and identify a specific antigens present on

13260-406: The moist, nutrient-rich environment. Sinusitis is an uncomfortable condition that may include congestion of mucus. A bacterial infection in sinusitis will cause discolored mucus and would respond to antibiotic treatment; viral infections typically resolve without treatment. Almost all sinusitis infections are viral and antibiotics are ineffective and not recommended for treating typical cases. In

13390-410: The most common infections; syphilis, gonorrhea, chlamydia, and trichomoniasis are curable, while HIV/AIDS and genital herpes are not curable. Some vaccinations may decrease the risk of certain infections including hepatitis B and few types of HPV . Safe sex practices such as use of condoms , having smaller number of sexual partners, and being in a relationship in which each person only has sex with

13520-494: The mucus greatly increase, thus inducing the polyelectrolyte effect and the swelling of the mucus. This swelling effect increases the pore size of the mucus and decreases mucus' viscosity, which allows bacteria to penetrate and migrate into the mucus and cause disease. The high selective permeability of mucus plays a crucial role in the healthy state of human beings by limiting the penetration of molecules, nutrients, pathogens, and drugs. The charge distribution within mucus serves as

13650-402: The mucus layer ultimately affects the periciliary liquid layer, which becomes dehydrated, compromising ciliary function, and impairing mucociliary clearance. A respiratory therapist can recommend airway clearance therapy which uses a number of clearance techniques to help with the clearance of mucus. In the lower respiratory tract excessive mucus production in the bronchi and bronchioles

13780-531: The number of new infections. The specific serological diagnostic identification, and later genotypic or molecular identification, of HIV also enabled the development of hypotheses as to the temporal and geographical origins of the virus, as well as a myriad of other hypothesis. The development of molecular diagnostic tools have enabled physicians and researchers to monitor the efficacy of treatment with anti-retroviral drugs . Molecular diagnostics are now commonly used to identify HIV in healthy people long before

13910-455: The onset of illness and have been used to demonstrate the existence of people who are genetically resistant to HIV infection. Thus, while there still is no cure for AIDS, there is great therapeutic and predictive benefit to identifying the virus and monitoring the virus levels within the blood of infected individuals, both for the patient and for the community at large. Symptomatic infections are apparent and clinical , whereas an infection that

14040-686: The other also decreases STIs risk. Comprehensive sex education may also be useful. STI diagnostic tests are usually easily available in the developed world , but they are often unavailable in the developing world . There is often shame and stigma associated with STIs. In 2015, STIs other than HIV resulted in 108,000 deaths worldwide. Globally, in 2015, about 1.1 billion people had STIs other than HIV/AIDS. About 500 million have either syphilis, gonorrhea, chlamydia or trichomoniasis. At least an additional 530 million have genital herpes, and 290 million women have human papillomavirus . Historical documentation of STIs in antiquity dates back to at least

14170-514: The other hand, some infectious agents are highly virulent. The prion causing mad cow disease and Creutzfeldt–Jakob disease invariably kills all animals and people that are infected. Persistent infections occur because the body is unable to clear the organism after the initial infection. Persistent infections are characterized by the continual presence of the infectious organism, often as latent infection with occasional recurrent relapses of active infection. There are some viruses that can maintain

14300-539: The pathogens are present but that no clinically apparent infection (no disease) is present. Different terms are used to describe how and where infections present over time. In an acute infection, symptoms develop rapidly; its course can either be rapid or protracted. In chronic infection, symptoms usually develop gradually over weeks or months and are slow to resolve. In subacute infections, symptoms take longer to develop than in acute infections but arise more quickly than those of chronic infections. A focal infection

14430-427: The penis with a properly worn condom from the vagina or anus effectively stops HIV transmission. An infected fluid to broken skin borne direct transmission of HIV would not be considered "sexually transmitted", but can still theoretically occur during sexual contact. This can be avoided simply by not engaging in sexual contact when presenting open, bleeding wounds. Other STIs, even viral infections, can be prevented with

14560-486: The person return the test for follow-up. Other facilities strongly encourage that those previously infected return to ensure that the infection has been eliminated. Novel strategies to foster re-testing have been the use of text messaging and email as reminders. These types of reminders are now used in addition to phone calls and letters. After obtaining a sexual history, a healthcare provider can encourage risk reduction by providing prevention counseling . Prevention counseling

14690-491: The post-classical education era the euphemistic effect was entirely lost, and the common abbreviation "VD" held only negative connotations. Other former euphemisms for STIs include "blood diseases" and "social diseases". The present euphemism is in the use of the initials "STI" rather than in the words they represent. The World Health Organization (WHO) has recommended the more inclusive term sexually transmitted infection since 1999. Public health officials originally introduced

14820-415: The prevailing more judgemental view and published her own research on improving sex education and maternity care. The first effective treatment for a sexually transmitted infection was salvarsan , a treatment for syphilis. With the discovery of antibiotics , a large number of sexually transmitted infections became easily curable, and this, combined with effective public health campaigns against STIs, led to

14950-440: The recommended method of diagnosis for gonorrhea and chlamydia. This can be done on either urine in both men and women, vaginal or cervical swabs in women, or urethral swabs in men. Screening can be performed: In the case of rape, the person can be treated prophylacticly with antibiotics. An option for treating partners of patients ( index cases ) diagnosed with chlamydia or gonorrhea is patient-delivered partner therapy , which

15080-406: The same as in 2016, but there were more than 20% increases in confirmed cases of gonorrhoea and syphilis. Since 2008 syphilis cases have risen by 148%, from 2,874 to 7,137, mostly among men who have sex with men . The number of first cases of genital warts in 2017 among girls aged 15–17 years was just 441, 90% less than in 2009 – attributed to the national HPV immunisation programme. AIDS is among

15210-658: The second half of the 19th century, the Contagious Diseases Acts were used to arrest suspected prostitutes. In 1924, a number of states concluded the Brussels Agreement , whereby states agreed to provide free or low-cost medical treatment at ports for merchant seamen with STIs. A proponent of these approaches was Nora Wattie , OBE, Venereal Diseases Officer in Glasgow from 1929, encouraged contact tracing and volunteering for treatment, rather than

15340-574: The sexual and reproductive health of adolescents. Incentive-based programmes may reduce adolescent pregnancy but more data is needed to confirm this. Specific age groups, persons who participate in risky sexual behavior, or those have certain health conditions may require screening. The CDC recommends that sexually active women under the age of 25 and those over 25 at risk should be screened for chlamydia and gonorrhea yearly. Appropriate times for screening are during regular pelvic examinations and preconception evaluations. Nucleic acid amplification tests are

15470-497: The sexual partner. There is no difference in reinfection prevention whether the sexual partner treated with medication without medical examination or after notification by patient. In 2008, it was estimated that 500 million people were infected with either syphilis, gonorrhea, chlamydia or trichomoniasis. At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus (HPV). STIs other than HIV resulted in 142,000 deaths in 2013. In

15600-457: The target antigen. To aid in the diagnosis of infectious diseases, immunoassays can detect or measure antigens from either infectious agents or proteins generated by an infected organism in response to a foreign agent. For example, immunoassay A may detect the presence of a surface protein from a virus particle. Immunoassay B on the other hand may detect or measure antibodies produced by an organism's immune system that are made to neutralize and allow

15730-559: The taxonomically classified pathogen genomes to generate an antimicrobial resistance profile – analogous to antibiotic sensitivity testing – to facilitate antimicrobial stewardship and allow for the optimization of treatment using the most effective drugs for a patient's infection. Metagenomic sequencing could prove especially useful for diagnosis when the patient is immunocompromised . An ever-wider array of infectious agents can cause serious harm to individuals with immunosuppression, so clinical screening must often be broader. Additionally,

15860-494: The term sexually transmitted infection , which clinicians are increasingly using alongside the term sexually transmitted disease in order to distinguish it from the former. Strategies for reducing STI risk include: vaccination, mutual monogamy , reducing the number of sexual partners, and abstinence. Also potentially helpful is behavioral counseling for sexually active adolescents and for adults who are at increased risk. Such interactive counseling, which can be resource-intensive,

15990-503: The test. For example, " Strep throat " is often diagnosed within minutes, and is based on the appearance of antigens made by the causative agent, S. pyogenes , that is retrieved from a patient's throat with a cotton swab. Serological tests, if available, are usually the preferred route of identification, however the tests are costly to develop and the reagents used in the test often require refrigeration . Some serological methods are extremely costly, although when commonly used, such as with

16120-430: The tunability of swelling effect is controlled by polyelectrolyte effect. Polymers with charged molecules are called polyelectrolytes . Mucins, a kind of polyelectrolyte proteoglycans , are the main component of mucus, which provides the polyelectrolyte effect in mucus. The process of inducing this effect comprises two steps: attraction of counter-ions and water compensation. When exposed in physiological ionic solution,

16250-436: The use of latex, polyurethane or polyisoprene condoms as a barrier. Some microorganisms and viruses are small enough to pass through the pores in natural skin condoms but are still too large to pass through latex or synthetic condoms. Proper male condom usage entails: In order to best protect oneself and the partner from STIs, the old condom and its contents are to be treated as infectious and properly disposed of. A new condom

16380-411: The use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. Chagas disease is the most significant example, because it is difficult to directly demonstrate the presence of

16510-466: The viscous nasal or airway mucus and prevented from entering the system. This process, together with the continual movement of the cilia on the respiratory epithelium toward the oropharynx ( mucociliary clearance ), helps prevent foreign objects from entering the lungs during breathing. This explains why coughing often occurs in those who smoke cigarettes. The body's natural reaction is to increase mucus production. In addition, mucus aids in moisturizing

16640-439: The warm air meets the colder outside temperature near the nostrils. This causes an excess amount of water to build up inside nasal cavities. In these cases, the excess fluid usually spills out externally through the nostrils. In the lower respiratory tract impaired mucociliary clearance due to conditions such as primary ciliary dyskinesia may result in mucus accumulation in the bronchi. The dysregulation of mucus homeostasis

16770-504: Was developed after the cervical diaphragm . Both cover the cervix and the main difference between the diaphragm and the cap is that the latter must be used only once, using a new one in each sexual act. The diaphragm, however, can be used more than once. These two devices partially protect against STIs (they do not protect against HIV). Researchers had hoped that nonoxynol-9 , a vaginal microbicide would help decrease STI risk. Trials, however, have found it ineffective and it may put women at

16900-485: Was first definitely recorded in Europe in 1495, its pustules often covered the body from the head to the knees, caused flesh to fall from people's faces, and led to death within a few months," rendering it far more fatal than it is today. Diamond concludes, "[B]y 1546, the disease had evolved into the disease with the symptoms so well known to us today." Gonorrhea is recorded at least up to 700 years ago and associated with

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