Sore throat , also known as throat pain , is pain or irritation of the throat . The majority of sore throats are caused by a virus, for which antibiotics are not helpful.
53-428: Influenza A virus subtype H7N7 (A/H7N7) is a subtype of Influenza A virus , a genus of Orthomyxovirus , the viruses responsible for influenza . Highly pathogenic strains (HPAI) and low pathogenic strains (LPAI) exist. H7N7 can infect humans, birds, pigs, seals , and horses in the wild; and has infected mice in laboratory studies. This unusual zoonotic potential represents a pandemic threat. In 2003, 89 people in
106-420: A cold , although usually more severe and less likely to include a runny nose . The onset of symptoms is sudden, and initial symptoms are predominately non-specific: a sudden fever; muscle aches; cough; fatigue; sore throat; headache; difficulty sleeping; loss of appetite; diarrhoea or abdominal pain; nausea and vomiting. Humans can rarely become infected with strains of avian or swine influenza , usually as
159-400: A zoonotic event. It is thought that all influenza A viruses causing outbreaks or pandemics among humans since the 1900s originated from strains circulating in wild aquatic birds through reassortment with other influenza strains. It is possible (though not certain) that pigs may act as an intermediate host for reassortment. The Global Influenza Surveillance and Response System (GISRS)
212-593: A common ancestor around 8,000 years ago. Outbreaks of influenza-like disease can be found throughout recorded history. The first probable record is by Hippocrates in 142 BCE. The historian Fujikawa listed 46 epidemics of flu-like illness in Japan between 862 and 1868. In Europe and the Americas, a number of epidemics were recorded through the Middle Ages and up to the end of the 19th century. In 1918-1919 came
265-428: A dry, hacking cough, depression, loss of appetite and weakness. EI is caused by two subtypes of influenza A viruses: H7N7 and H3N8, which have evolved from avian influenza A viruses. Most animals infected with canine influenza A will show symptoms such as coughing, runny nose, fever, lethargy, eye discharge, and a reduced appetite lasting anywhere from 2–3 weeks. There are two different influenza A dog flu viruses: one
318-462: A layer between the nucleoprotein and the envelope, called the capsid . Envelope - The viral envelope consists of a lipid bilayer derived from the host cell. Two viral proteins; hemagglutinin (HA) and neuraminidase (NA), are inserted into the envelope and are exposed as spikes on the surface of the virion. Both proteins are antigenic ; a host's immune system can react to them and produce antibodies in response. The M2 protein forms an ion channel in
371-669: A lipid envelope. The virus particle (also called the virion ) is 80–120 nanometers in diameter such that the smallest virions adopt an elliptical shape; larger virions have a filamentous shape. Core - The central core of the virion contains the viral RNA genome, which is made of eight separate segments. The nucleoprotein (NP) coats the viral RNA to form a ribonucleoprotein that assumes a helical (spiral) configuration. Three large proteins (PB 1 , PB 2 , and PA), which are responsible for RNA transcription and replication, are bound to each segment of viral RNP. Capsid - The matrix protein M1 forms
424-404: A mechanism called cap-snatching . It consists in the hijacking and cleavage of host capped pre-mRNAs . Host cell mRNA is cleaved near the cap to yield a primer for the transcription of positive-sense viral mRNA using the negative-sense viral RNA as a template. The host cell then transports the viral mRNA into the cytoplasm where ribosomes manufacture the viral proteins. Replication of
477-593: A pandemic in 2009. Because of its close resemblance to some strains circulating in pigs, this became known as " Swine flu " Influenza A virus continues to circulate and evolve in birds and pigs. Almost all possible combinations of H (1 thru 16) and N (1 thru 11) have been isolated from wild birds. As of June 2024, two particularly virulent IAV strains - H5N1 and H7N9 - are predominant in wild bird populations. These frequently cause outbreaks in domestic poultry, with occasional spillover infections in humans who are in close contact with poultry. Influenza viruses have
530-467: A poultry farm in Voorthuizen in the central Netherlands. As a precautionary measure, 25,000 chickens were culled from Voorthuizen and surrounding farms. In June 2008, high pathogenic (HP) H7N7 was confirmed on a 25,000-bird laying unit at Shenington , England; probably derived from a pre-existing low pathogenic variety. Farmers Guardian reported a 2.5 per cent increased mortality in one shed and
583-647: A reduction in egg production recorded two weeks before numerous deaths on 2 June that led to the diagnosis of HP H7N7 on 4 June. In October 2009, high pathogenic (HP) H7N7 was confirmed on a farm in Almoguera , Guadalajara , Spain. Hong Kong announced that it would suspend the import of poultry from Spain. In August 2013, high pathogenic (HP) H7N7 was found in markets in Wenzhou , Zhejiang province in China when testing for H7N9. In July 2015, high pathogenic (HP) H7N7
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#1732798696792636-467: A relatively high mutation rate that is characteristic of RNA viruses . The segmentation of the influenza A virus genome facilitates genetic recombination by segment reassortment in hosts who become infected with two different strains of influenza viruses at the same time. With reassortment between strains, an avian strain which does not affect humans may acquire characteristics from a different strain which enable it to infect and pass between humans -
689-407: A result of close contact with infected animals or contaminated material; symptoms generally resemble seasonal flu but occasionally can be severe including death. Some species of wild aquatic birds act as natural asymptomatic carriers of a large variety of influenza A viruses, which they can spread over large distances in their annual migration. Symptoms of avian influenza vary according to both
742-474: A result of close contact with infected animals; symptoms range from mild to severe including death. Bird-adapted strains of the virus can be asymptomatic in some aquatic birds but lethal if they spread to other species, such as chickens. IAV disease in poultry can be can be prevented by vaccination, however biosecurity control measures are preferred. In humans, seasonal influenza can be treated in its early stages with antiviral medicines. A global network,
795-644: A type-1 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein. Almost all possible combinations of H (1 thru 16) and N (1 thru 11) have been isolated from wild birds. Further variations exist within the subtypes and can lead to very significant differences in the virus's ability to infect and cause disease, as well as to the severity of symptoms. Symptoms of human seasonal flu usually include fever, cough, sore throat , muscle aches , conjunctivitis and, in severe cases, breathing problems and pneumonia that may be fatal. Humans can rarely become infected with strains of avian or swine influenza , usually as
848-491: A type-5 hemagglutinin (H) protein and a type-1 neuraminidase (N) protein. Further variations exist within the subtypes and can lead to very significant differences in the virus's behavior. By definition, the subtyping scheme only takes into account the two outer proteins, not the at least 8 proteins internal to the virus. Almost all possible combinations of H (1 thru 16) and N (1 thru 11) have been isolated from wild birds. H17 and H18 have only been discovered in bats. Due to
901-406: A viral infection of the throat. Other causes include other bacterial infections (such as group A streptococcus or streptococcal pharyngitis ), trauma, and tumors . Gastroesophageal (acid) reflux disease can cause stomach acid to back up into the throat and also cause the throat to become sore. In children, streptococcal pharyngitis is the cause of 35–37% of sore throats. The symptoms of
954-431: A viral infection and a bacterial infection may be very similar. Some clinical guidelines suggest that the cause of a sore throat is confirmed prior to prescribing antibiotic therapy and only recommend antibiotics for children who are at high risk of non- suppurative complications. A group A streptococcus infection can be diagnosed by throat culture or a rapid test: Clinicians often also make treatment decisions based on
1007-576: Is a global network of laboratories that monitor the spread of influenza with the aim to provide the World Health Organization with influenza control information and to inform vaccine development. Several millions of specimens are tested by the GISRS network annually through a network of laboratories in 127 countries. As well as human viruses, GISRS monitors avian, swine, and other potentially zoonotic influenza viruses. Flu season
1060-453: Is an enveloped negative-sense RNA virus , with a segmented genome. Through a combination of mutation and genetic reassortment the virus can evolve to acquire new characteristics, enabling it to evade host immunity and occasionally to jump from one species of host to another. Subtypes of IAV are defined by the combination of the antigenic H and N proteins in the viral envelope ; for example, " H1N1 " designates an IAV subtype that has
1113-455: Is an H3N8 virus and the other is an H3N2 virus. The H3N8 strain has evolved from an equine influenza avian virus which has adapted to sustained transmission among dogs. The H3N2 strain is derived from an avian influenza which jumped to dogs in 2004 in either Korea or China. It is likely that the virus persists in both animal shelters and kennels, as well as in farms where dogs are raised for meat production. The first bat flu virus, IAV(H17N10),
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#17327986967921166-588: Is an annually recurring time period characterized by the prevalence of an outbreak of influenza , caused either by Influenza A or by Influenza B . The season occurs during the cold half of the year in temperate regions; November through February in the northern hemisphere and May to October in the southern hemisphere. Flu seasons also exist in the tropics and subtropics , with variability from region to region. Annually, about 3 to 5 million cases of severe illness and 290,000 to 650,000 deaths from seasonal flu occur worldwide. There are several possible reasons for
1219-676: Is based solely on the effect on chickens - a virus strain is highly pathogenic avian influenza ( HPAI ) if 75% or more of chickens die after being deliberately infected with it, or if it is genetically similar to such a strain. The alternative classification is low pathogenic avian influenza (LPAI). Classification of a virus strain as either LPAI or HPAI is based on the severity of symptoms in domestic chickens and does not predict severity of symptoms in other species. Chickens infected with LPAI display mild symptoms or are asymptomatic , whereas HPAI causes serious breathing difficulties, significant drop in egg production, and sudden death. Since 2006,
1272-511: Is concern about two subtypes of avian influenza which are circulating in wild bird populations worldwide, H5N1 and H7N9 . Both of these have potential to devastate poultry stocks, and both have jumped to humans with relatively high case fatality rates . H5N1 in particular has infected a wide range of mammals and may be adapting to mammalian hosts. As of June 2024, the influenza viruses which circulate widely in humans are IAV subtypes H1N1 and H3N2, together with Influenza B. Annual vaccination
1325-437: Is not known whether antibiotics are effective for preventing recurrent sore throat. There is only limited evidence that a hot drink can help alleviate a sore throat, and other common cold and influenza symptoms. If the sore throat is unrelated to a cold and is caused by, for example, tonsillitis , a cold drink may be helpful. There are also other medications such as lozenges which can help soothe irritated tissues of
1378-596: Is possible to vaccinate poultry and pigs against specific strains of influenza. Vaccination should be combined with other control measures such as infection monitoring, early detection and biosecurity. The main treatment for mild influenza is supportive; rest, fluids, and over-the-counter medicines to alleviate symptoms while the body's own immune system works to recover from infection. Antiviral drugs are recommended for those with severe symptoms, or for those who are at risk of developing complications such as pneumonia. The symptoms of seasonal flu are similar to those of
1431-438: Is spread either through close contact between animals or by the movement of contaminated equipment between farms. Humans who are in close contact with pigs can sometimes become infected. Equine influenza can affect horses, donkeys, and mules; it has a very high rate of transmission among horses, and a relatively short incubation time of one to three days. Clinical signs of equine influenza include fever, nasal discharge, have
1484-443: Is the primary and most effective way to prevent influenza and influenza-associated complications, especially for high-risk groups. Vaccines against the flu are trivalent or quadrivalent, providing protection against the dominant strains of IAV(H1N1) and IAV(H3N2), and one or two influenza B virus strains; the formulation is continually reviewed in order to match the predominant strains in circulation. Poultry and other animals - it
1537-572: The Global Influenza Surveillance and Response System (GISRS) monitors the spread of influenza with the aim to inform development of both seasonal and pandemic vaccines. Several millions of specimens are tested by the GISRS network annually through a network of laboratories in 127 countries. As well as human viruses, GISRS monitors avian, swine, and other potentially zoonotic influenza viruses. IAV vaccines need to be reformulated regularly in order to keep up with changes in
1590-584: The World Organization for Animal Health requires all detections of LPAI H5 and H7 subtypes to be reported because of their potential to mutate into highly pathogenic strains. Signs of swine flu in pigs can include fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed. Some pigs infected with influenza, however, may show no signs of illness at all. Swine flu subtypes are principally H1N1, H1N2, and H3N2; it
1643-436: The management of pain . The use of corticosteroids seems to increase slightly the likelihood of resolution and the reduction of pain, but more analysis is necessary to ensure that this minimal benefit outweighs the risks. Antibiotics probably reduce pain, diminish headaches and could prevent some sore throat complications, but as these effects are small they must be balanced with the threat of antimicrobial resistance. It
Influenza A virus subtype H7N7 - Misplaced Pages Continue
1696-460: The Dutch government: As at least 50% of the people exposed to infected poultry had H7 antibodies detectable with the modified assay, it was estimated that avian influenza A/H7N7 virus infection occurred in at least 1000, and perhaps as many as 2000 people. The seroprevalence of H7 antibodies in people without contact with infected poultry, but with close household contact to an infected poultry worker,
1749-469: The Netherlands were confirmed to have been infected by H7N7 following an outbreak in poultry on approximately 255 farms. One death was recorded – a veterinarian who had been testing chickens for the virus – and all infected flocks were culled. Most affected people had mild symptoms including conjunctivitis . Antibodies were found in over half of 500 people tested according to the final official report by
1802-487: The United States, about 1% of all visits to the hospital emergency department, physician office and medical clinics, and outpatient clinics are for sore throat (over 7 million visits for adults and 7 million visits for children per year). Causes of sore throat include: A sore throat is pain felt anywhere in the throat. Symptoms of sore throat include: The most common cause (80%) is acute viral pharyngitis,
1855-427: The core of new virions. The predominant natural reservoir of influenza viruses is thought to be wild waterfowl. The subtypes of influenza A virus are estimated to have diverged 2,000 years ago. Influenza viruses A and B are estimated to have diverged from a single ancestor around 4,000 years ago, while the ancestor of influenza viruses A and B and the ancestor of influenza virus C are estimated to have diverged from
1908-409: The envelope and is responsible for uncoating the virion once it has bound to a host cell. The table below presents a concise summary of the influenza genome and the principal functions of the proteins which are encoded. Segments are conventionally numbered from 1 to 8 in descending order of length. PB2 also inhibits JAK1/STAT signaling to inhibit host innate immune response It also degrades
1961-515: The feverPAIN. A clinical scoring system is often used along with a rapid test. The scoring systems use observed signs and symptoms in order to determine the likelihood of a bacterial infection. Sore or scratchy throat can temporarily be relieved by gargling a solution of 1/4 to 1/2 teaspoon (1.3 to 2.5 milliliters) salt dissolved in an 8-US-fluid-ounce (240 ml) glass of water. Pain medications such as non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol (acetaminophen) help in
2014-475: The first flu pandemic of the 20th century, known generally as the " Spanish flu ", which caused an estimated 20 to 50 million deaths worldwide. It is now known that this was caused by an immunologically novel H1N1 subtype of influenza A. The next pandemic took place in 1957, the " Asian flu ", which was caused by a H2N2 subtype of the virus in which the genome segments coding for HA and NA appeared to have derived from avian influenza strains by reassortment, while
2067-486: The high variability of the virus, subtyping is not sufficient to uniquely identify a strain of influenza A virus. To unambiguously describe a specific isolate of virus, researchers use the Influenza virus nomenclature, which describes, among other things, the subtype, year, and place of collection. Some examples include: The influenza A virus has a negative-sense , single-stranded, segmented RNA genome , enclosed in
2120-575: The host cell's mitochondrial antiviral signaling protein At the early stage of infection, the RNP binds to the host cell's importin-α which transports it into the host cell nucleus, where the viral RNA is transcribed and replicated. At a later stage of infection, newly manufactured viral RNA segments assemble with the NP protein and polymerase (PB1, PB2 and PA) to form the core of a progeny virion NA also facilitates
2173-531: The movement of infective virus particles through mucus, enabling them to reach host epithelial cells. M1 also assists with the function of the NEP protein. Three viral proteins - PB1, PB2, and PA - associate to form the RNA-dependent RNA polymerase (RdRp) which functions to transcribe and replicate the viral RNA. Viral messenger RNA Transcription - The RdRp complex transcribes viral mRNAs by using
Influenza A virus subtype H7N7 - Misplaced Pages Continue
2226-403: The person get better faster, reduce the risk that the bacterial infection spreads, prevent retropharyngeal abscesses and quinsy , and reduce the risk of other complications such as rheumatic fever and rheumatic heart disease . In most developed countries , post-streptococcal diseases have become far less common. For this reason, awareness and public health initiatives to promote minimizing
2279-471: The person's signs and symptoms alone. In the US, approximately two-thirds of adults and half of children with sore throat are diagnosed based on symptoms and do not have testing for the presence of GAS to confirm a bacterial infection. Numerous clinical scoring systems ( decision tools ) have also been developed to support clinical decisions. Scoring systems that have been proposed include Centor's , McIsaac's, and
2332-460: The relationship between influenza viruses and bacteria, how influenza symptoms progress, and why some influenza viruses are deadlier than others. Past pandemics, and especially the 1918 pandemic, are the subject of much research to understand and prevent flu pandemics. The World Health Organization has published a Research Agenda with five streams: Sore throat For sore throat caused by bacteria (GAS), treatment with antibiotics may help
2385-513: The remainder of the genome was descended from the 1918 virus. The 1968 pandemic (" Hong Kong flu " ) was caused by a H3N2 subtype in which the NA segment was derived from the 1957 virus, while the HA segment had been reassorted from an avian strain of influenza. In the 21st century, a strain of H1N1 flu (since titled H1N1pdm09 ) which was antigenically very different from previous H1N1 strains, leading to
2438-492: The strain of virus underlying the infection, and on the species of bird affected. Symptoms of influenza in birds may include swollen head, watery eyes, unresponsiveness, lack of coordination, respiratory distress such as sneezing or gurgling. Because of the impact of avian influenza on economically important chicken farms, avian virus strains are classified as either highly pathogenic (and therefore potentially requiring vigorous control measures) or low pathogenic. The test for this
2491-488: The use of antibiotics for viral infections have become the focus. Approximately 35% of childhood sore throats and 5–25% of cases in adults are caused by a bacterial infection from group A streptococcus. Sore throats that are "non-group A streptococcus" are assumed to be caused by a viral infection. Sore throat is a common reason for people to visit their primary care doctors and the top reason for antibiotic prescriptions by primary care practitioners such as family doctors. In
2544-417: The viral RNA - The replication of the influenza virus, unlike most other RNA viruses , takes place in the nucleus and involves two steps. The RdRp first of all transcribes the negative-sense viral genome into a positive-sense complimentary RNA (cRNA), then the cRNAs are used as templates to transcribe new negative-sense vRNA copies. These are exported from the nucleus and assemble near the cell membrane to form
2597-622: The virus. There are two methods of classification, one based on surface proteins (originally serotypes ), and the other based on its behavior, mainly the host animal . There are two antigenic proteins on the surface of the viral envelope, hemagglutinin and neuraminidase . Different influenza virus genomes encode different hemagglutinin and neuraminidase proteins. Based on their serotype , there are 18 known types of hemagglutinin and 11 types of neuraminidase. Subtypes of IAV are classified by their combination of H and N proteins. For example, " H5N1 " designates an influenza A subtype that has
2650-949: The winter peak in temperate regions: A zoonosis a disease in a human caused by a pathogen (such as a bacterium , or virus ) that has jumped from a non-human to a human . Avian and pig influenza viruses can, on rare occasions, transmit to humans and cause zoonotic influenza virus infections; these infections are usually confined to people who have been in close contact with infected animals or material such as infected feces and meat, they do not spread to other humans. Symptoms of these infections in humans vary greatly; some are in asymptomatic or mild while others can cause severe disease, leading to severe pneumonia and death. A wide range of Influenza A virus subtypes have been found to cause zoonotic disease. Zoonotic infections can be prevented by good hygiene, by preventing farmed animals from coming into contact with wild animals, and by using appropriate personal protective equipment. As of June 2024, there
2703-417: Was 59%. This suggests that the population at risk for avian influenza was not limited to those with direct contact to infected poultry, and that person to person transmission may have occurred on a large scale. Final analysis of Dutch avian influenza outbreaks reveals much higher levels of transmission to humans than previously thought. In August 2006, low pathogenic (LP) H7N7 was found during routine testing at
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#17327986967922756-707: Was confirmed on a poultry farm in Lancashire , England . In August 2020, H7N7 was confirmed on a free range farm in Lethbridge, Victoria . Influenza A virus Influenza A virus (IAV) is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae . It is a pathogen with strains that infect birds and some mammals , as well as causing seasonal flu in humans. Mammals in which different strains of IAV circulate with sustained transmission are bats, pigs, horses and dogs; other mammals can occasionally become infected. IAV
2809-465: Was first discovered in 2009 in little yellow-shouldered bats ( Sturnira lilium ) in Guatemala . In 2012 a second bat influenza A virus IAV(H18N11) was discovered in flat-faced fruit-eating bats ( Artibeus planirostris ) from Peru . Bat influenza viruses have been found to be poorly adapted to non-bat species. Influenza research includes efforts to understand how influenza viruses enter hosts,
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