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80-571: The middle school, the high school, and the Bedford Central School District administrative buildings are all on the Fox Lane High School campus, near Interstate 684. The campus includes three soccer fields, a multipurpose astroturf field, a track that encircles the multipurpose field, and several baseball diamonds. The superintendent of the district is Dr. Robert Glass. Several old school buildings within

160-405: A bone marrow transplant , in which (undifferentiated) hematopoietic stem cells are transferred. When B cells and T cells are activated by a pathogen, memory B-cells and T- cells develop, and the primary immune response results. Throughout the lifetime of an animal, these memory cells will "remember" each specific pathogen encountered, and can mount a strong secondary response if the pathogen

240-418: A pathogen or toxin are transferred to non- immune individuals. Passive immunization is used when there is a high risk of infection and insufficient time for the body to develop its own immune response, or to reduce the symptoms of ongoing or immunosuppressive diseases. Passive immunity provides immediate protection, but the body does not develop memory, therefore the patient is at risk of being infected by

320-401: A vaccine , a substance that contains antigen. A vaccine stimulates a primary response against the antigen without causing symptoms of the disease. The term vaccination was coined by Richard Dunning, a colleague of Edward Jenner , and adapted by Louis Pasteur for his pioneering work in vaccination. The method Pasteur used entailed treating the infectious agents for those diseases, so they lost

400-404: A century to treat infectious disease, and before the advent of antibiotics , was often the only specific treatment for certain infections. Immunoglobulin therapy continued to be a first line therapy in the treatment of severe respiratory diseases until the 1930s, even after sulfonamide lot antibiotics were introduced. Passive or " adoptive transfer " of cell-mediated immunity, is conferred by

480-511: A combination of short-term notes and long-term bonds, and with an intent to minimize the increase in tax levy to homeowners and the length of time during which the dollar amount of that increase will apply. The project was slated to begin as soon as possible, and was expected to be completed in 2016. Large portions of the plan call for renovations at West Patent Elementary School and the Fox Lane Campus. These were to include renovations for

560-474: A family of viruses. By 12 January 2020, five genomes of SARS‑CoV‑2 had been isolated from Wuhan and reported by the Chinese Center for Disease Control and Prevention (CCDC) and other institutions; the number of genomes increased to 42 by 30 January 2020. A phylogenetic analysis of those samples showed they were "highly related with at most seven mutations relative to a common ancestor ", implying that

640-399: A full theory of immunity was Ilya Mechnikov who revealed phagocytosis in 1882. With Louis Pasteur 's germ theory of disease , the fledgling science of immunology began to explain how bacteria caused disease, and how, following infection, the human body gained the ability to resist further infections. In 1888 Emile Roux and Alexandre Yersin isolated diphtheria toxin , and following

720-413: A mink euthanasia campaign rendering it virtually extinct. Each SARS-CoV-2 virion is 60–140 nanometres (2.4 × 10 –5.5 × 10  in) in diameter; its mass within the global human populace has been estimated as being between 0.1 and 10 kilograms. Like other coronaviruses, SARS-CoV-2 has four structural proteins, known as the S ( spike ), E ( envelope ), M ( membrane ), and N ( nucleocapsid ) proteins;

800-499: A range of animals—such as cats, ferrets, hamsters, non-human primates, minks, tree shrews, raccoon dogs, fruit bats, and rabbits—that are susceptible and permissive to SARS-CoV-2 infection. Some institutions have advised that those infected with SARS‑CoV‑2 restrict their contact with animals. On 1   February 2020, the World Health Organization (WHO) indicated that "transmission from asymptomatic cases

880-430: A single linear RNA segment. Coronaviruses infect humans, other mammals, including livestock and companion animals, and avian species. Human coronaviruses are capable of causing illnesses ranging from the common cold to more severe diseases such as Middle East respiratory syndrome (MERS, fatality rate ~34%). SARS-CoV-2 is the seventh known coronavirus to infect people, after 229E , NL63 , OC43 , HKU1 , MERS-CoV , and

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960-412: A site. The furin cleavage site PRRAR↓ is highly similar to that of the feline coronavirus , an alphacoronavirus 1 strain. Viral genetic sequence data can provide critical information about whether viruses separated by time and space are likely to be epidemiologically linked. With a sufficient number of sequenced genomes , it is possible to reconstruct a phylogenetic tree of the mutation history of

1040-479: Is acquired through the exposure to a pathogen, which triggers the production of antibodies by the immune system. Passive immunity is acquired through the transfer of antibodies or activated T-cells derived from an immune host either artificially or through the placenta; it is short-lived, requiring booster doses for continued immunity. The diagram below summarizes these divisions of immunity. Adaptive immunity recognizes more diverse patterns. Unlike innate immunity it

1120-508: Is airborne and primarily spreads between people through close contact and via aerosols and respiratory droplets that are exhaled when talking, breathing, or otherwise exhaling, as well as those produced from coughs and sneezes. It enters human cells by binding to angiotensin-converting enzyme 2 (ACE2), a membrane protein that regulates the renin–angiotensin system. During the initial outbreak in Wuhan , China, various names were used for

1200-478: Is also found in the epic poem " Pharsalia " written around 60 BC by the poet Marcus Annaeus Lucanus to describe a North African tribe's resistance to snake venom . The first clinical description of immunity which arose from a specific disease-causing organism is probably A Treatise on Smallpox and Measles ("Kitab fi al-jadari wa-al-hasbah″, translated 1848 ) written by the Islamic physician Al-Razi in

1280-571: Is also provided through the transfer of IgA antibodies found in breast milk that are transferred to the gut of a nursing infant, protecting against bacterial infections, until the newborn can synthesize its antibodies. Colostrum present in mothers milk is an example of passive immunity. Artificially acquired passive immunity is a short-term immunization induced by the transfer of antibodies, which can be administered in several forms; as human or animal blood plasma, as pooled human immunoglobulin for intravenous ( IVIG ) or intramuscular (IG) use, and in

1360-469: Is also said to have sought to create a 'universal antidote' to protect him from all poisons. For nearly 2000 years, poisons were thought to be the proximate cause of disease, and a complicated mixture of ingredients, called Mithridate , was used to cure poisoning during the Renaissance . An updated version of this cure, Theriacum Andromachi , was used well into the 19th century. The term "immunes"

1440-477: Is another possible cause of infection. Preliminary research indicates that the virus may remain viable on plastic ( polypropylene ) and stainless steel ( AISI 304 ) for up to three days, but it does not survive on cardboard for more than one day or on copper for more than four hours. The virus is inactivated by soap, which destabilizes its lipid bilayer . Viral RNA has also been found in stool samples and semen from infected individuals. The degree to which

1520-425: Is approximately 30,000 bases in length, relatively long for a coronavirus—which in turn carry the largest genomes among all RNA families. Its genome consists nearly entirely of protein-coding sequences, a trait shared with other coronaviruses. A distinguishing feature of SARS‑CoV‑2 is its incorporation of a polybasic site cleaved by furin , which appears to be an important element enhancing its virulence. It

1600-413: Is associated with memory of the pathogen. For thousands of years mankind has been intrigued with the causes of disease and the concept of immunity. The prehistoric view was that disease was caused by supernatural forces, and that illness was a form of theurgic punishment for "bad deeds" or "evil thoughts" visited upon the soul by the gods or by one's enemies. In Classical Greek times, Hippocrates , who

1680-414: Is defined as the first line of defense against pathogens, representing a critical systemic response to prevent infection and maintain homeostasis, contributing to the activation of an adaptive immune response. It does not adapt to specific external stimulus or a prior infection, but relies on genetically encoded recognition of particular patterns. Adaptive or acquired immunity is the active component of

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1760-419: Is detected again. The primary and secondary responses were first described in 1921 by English immunologist Alexander Glenny although the mechanism involved was not discovered until later. This type of immunity is both active and adaptive because the body's immune system prepares itself for future challenges. Active immunity often involves both the cell-mediated and humoral aspects of immunity as well as input from

1840-453: Is likely not a major driver of transmission". One meta-analysis found that 17% of infections are asymptomatic, and asymptomatic individuals were 42% less likely to transmit the virus. However, an epidemiological model of the beginning of the outbreak in China suggested that "pre-symptomatic shedding may be typical among documented infections" and that subclinical infections may have been

1920-437: Is present in all metazoans , immune responses: inflammatory responses and phagocytosis . The adaptive component, on the other hand, involves more advanced lymphatic cells that can distinguish between specific "non-self" substances in the presence of "self". The reaction to foreign substances is etymologically described as inflammation while the non-reaction to self substances is described as immunity. The two components of

2000-559: Is regarded as the Father of Medicine, diseases were attributed to an alteration or imbalance in one of the four humors (blood, phlegm, yellow bile or black bile). The first written descriptions of the concept of immunity may have been made by the Athenian Thucydides who, in 430 BC, described that when the plague hit Athens : "the sick and the dying were tended by the pitying care of those who had recovered, because they knew

2080-558: Is required for defense of tuberculosis in humans. Individuals with genetic defects in TNF may get recurrent and life-threatening infections with tuberculosis bacteria ( Mycobacterium tuberculosis ) but are otherwise healthy. They also seem to respond to other infections more or less normally. The condition is therefore called Mendelian susceptibility to mycobacterial disease (MSMD) and variants of it can be caused by other genes related to interferon production or signaling (e.g. by mutations in

2160-576: Is the protein responsible for allowing the virus to attach to and fuse with the membrane of a host cell; specifically, its S1 subunit catalyzes attachment, the S2 subunit fusion. Immunity (medical) In biology , immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease . Immunity may occur naturally or be produced by prior exposure or immunization . The immune system has innate and adaptive components. Innate immunity

2240-431: Is thought to have assumed that those animals acquired some detoxifying property, so that their blood would contain transformed components of the snake venom that could induce resistance to it instead of exerting a toxic effect. Mithridates reasoned that, by drinking the blood of these animals, he could acquire a similar resistance. Fearing assassination by poison, he took daily sub-lethal doses of venom to build tolerance. He

2320-651: Is unknown, but, about 1000 AD, the Chinese began practicing a form of immunization by drying and inhaling powders derived from the crusts of smallpox lesions. Around the 15th century in India , the Ottoman Empire , and east Africa , the practice of inoculation (poking the skin with powdered material derived from smallpox crusts) was quite common. This practice was first introduced into the west in 1721 by Lady Mary Wortley Montagu [the phrase "first introduced into

2400-553: The 2002–2004 SARS outbreak . There are animal-borne coronavirus strains more closely related to SARS-CoV-2, the most closely known relative being the BANAL-52 bat coronavirus. SARS-CoV-2 is of zoonotic origin; its close genetic similarity to bat coronaviruses suggests it emerged from such a bat-borne virus . Research is ongoing as to whether SARS‑CoV‑2 came directly from bats or indirectly through any intermediate hosts. The virus shows little genetic diversity , indicating that

2480-547: The Centers for Disease Control and Prevention (CDC) concluded that "Multiple studies in different settings have consistently shown that infection with SARS-CoV-2 and vaccination each result in a low risk of subsequent infection with antigenically similar variants for at least 6 months. Numerous immunologic studies and a growing number of epidemiologic studies have shown that vaccinating previously infected individuals significantly enhances their immune response and effectively reduces

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2560-725: The International Committee on Taxonomy of Viruses adopted the official name "severe acute respiratory syndrome coronavirus 2" (SARS‑CoV‑2). To avoid confusion with the disease SARS , the WHO sometimes refers to SARS‑CoV‑2 as "the COVID-19 virus" in public health communications and the name HCoV-19 was included in some research articles. Referring to COVID-19 as the "Wuhan virus" has been described as dangerous by WHO officials, and as xenophobic by many journalists and academics. Human-to-human transmission of SARS‑CoV‑2

2640-469: The index case ". The authors later published a correction that showed that shedding began earlier than first estimated, four to five days before symptoms appear. There is uncertainty about reinfection and long-term immunity. It is not known how common reinfection is, but reports have indicated that it is occurring with variable severity. The first reported case of reinfection was a 33-year-old man from Hong Kong who first tested positive on 26 March 2020,

2720-461: The innate immune system . Naturally acquired active immunity occurs as the result of an infection. When a person is exposed to a live pathogen and develops a primary immune response , this leads to immunological memory. Many disorders of immune system function can affect the formation of active immunity, such as immunodeficiency (both acquired and congenital forms) and immunosuppression . Artificially acquired active immunity can be induced by

2800-483: The nasal cavity is seemingly the dominant initial site of infection, with subsequent aspiration -mediated virus-seeding into the lungs in SARS‑CoV‑2 pathogenesis. They found that there was an infection gradient from high in proximal towards low in distal pulmonary epithelial cultures, with a focal infection in ciliated cells and type 2 pneumocytes in the airway and alveolar regions respectively. Studies have identified

2880-420: The spillover event introducing SARS‑CoV‑2 to humans is likely to have occurred in late 2019. Epidemiological studies estimate that in the period between December 2019 and September 2020 each infection resulted in an average of 2.4–3.4 new infections when no members of the community were immune and no preventive measures were taken. However, some subsequent variants have become more infectious. The virus

2960-412: The 1890 discovery by Behring and Kitasato of antitoxin based immunity to diphtheria and tetanus , the antitoxin became the first major success of modern therapeutic immunology. In Europe , the induction of active immunity emerged in an attempt to contain smallpox . Immunization has existed in various forms for at least a thousand years, without the terminology. The earliest use of immunization

3040-600: The 2020–2021 school year and returned to full in-person instruction in April 2021. SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 ( SARS‑CoV‑2 ) is a strain of coronavirus that causes COVID-19 , the respiratory illness responsible for the COVID-19 pandemic . The virus previously had the provisional name 2019 novel coronavirus ( 2019-nCoV ), and has also been called human coronavirus 2019 ( HCoV-19 or hCoV-19 ). First identified in

3120-497: The 9th century. In the treatise, Al Razi describes the clinical presentation of smallpox and measles and goes on to indicate that exposure to these specific agents confers lasting immunity (although he does not use this term). Until the 19th century, the miasma theory was also widely accepted. The theory viewed diseases such as cholera or the Black Plague as being caused by a miasma, a noxious form of "bad air". If someone

3200-495: The N protein holds the RNA genome, and the S, E, and M proteins together create the viral envelope . Coronavirus S proteins are glycoproteins and also type I membrane proteins (membranes containing a single transmembrane domain oriented on the extracellular side). They are divided into two functional parts (S1 and S2). In SARS-CoV-2, the spike protein, which has been imaged at the atomic level using cryogenic electron microscopy ,

3280-401: The SARS‑CoV‑2 genome (matches above 90 percent may sound high, but in genomic terms it is a wide evolutionary gap ). In addition, despite similarities in a few critical amino acids, pangolin virus samples exhibit poor binding to the human ACE2 receptor. SARS‑CoV‑2 belongs to the broad family of viruses known as coronaviruses . It is a positive-sense single-stranded RNA (+ssRNA) virus, with

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3360-708: The ability to cause serious disease. Pasteur adopted the name vaccine as a generic term in honor of Jenner's discovery, which Pasteur's work built upon. In 1807, Bavaria became the first group to require their military recruits to be vaccinated against smallpox, as the spread of smallpox was linked to combat. Subsequently, the practice of vaccination would increase with the spread of war. There are four types of traditional vaccines : In addition, there are some newer types of vaccines in use: A variety of vaccine types are under development; see Experimental Vaccine Types . Most vaccines are given by hypodermic or intramuscular injection as they are not absorbed reliably through

3440-598: The amino acid sequence P RR A . This sequence is upstream of an arginine and serine which forms the S1/S2 cleavage site ( P RR A R ↓ S ) of the spike protein. Although such sites are a common naturally-occurring feature of other viruses within the Subfamily Orthocoronavirinae, it appears in few other viruses from the Beta-CoV genus, and it is unique among members of its subgenus for such

3520-404: The city of Wuhan , Hubei, China, the World Health Organization designated the outbreak a public health emergency of international concern from January 30, 2020, to May 5, 2023. SARS‑CoV‑2 is a positive-sense single-stranded RNA virus that is contagious in humans. SARS‑CoV‑2 is a strain of the species Betacoronavirus pandemicum (SARSr-CoV), as is SARS-CoV-1 , the virus that caused

3600-413: The course of the disease and were themselves free from apprehensions. For no one was ever attacked a second time, or not with a fatal result". Active immunotherapy may have begun with Mithridates VI of Pontus (120-63 BC) who, to induce active immunity for snake venom, recommended using a method similar to modern toxoid serum therapy , by drinking the blood of animals which fed on venomous snakes. He

3680-418: The differences between what was then called 2019-nCoV and the virus from the 2003 SARS outbreak were insufficient to make them separate viral species . Therefore, they identified 2019-nCoV as a virus of Severe acute respiratory syndrome–related coronavirus . In July 2020, scientists reported that a more infectious SARS‑CoV‑2 variant with spike protein variant G614 has replaced D614 as the dominant form in

3760-596: The district were in a state of disrepair, including West Patent Elementary School and Fox Lane Middle School. Both were in need of new roofs, electrical work and more. On October 22, 2013, voters in the Town of Bedford who were members of the Bedford Central School District approved a $ 31,828,238 Capital Improvement Project proposed by the Bedford Central School District. The approval was by a wide margin. A total of 1,825 votes were cast, with 1,197 votes in favor and 628 votes against. The Capital Improvement Project will be funded with

3840-452: The face of some opposition. However, inoculation had been reported in Wales since the early 17th century"]. In 1798, Edward Jenner introduced the far safer method of deliberate infection with cowpox virus, ( smallpox vaccine ), which caused a mild infection that also induced immunity to smallpox. By 1800, the procedure was referred to as vaccination . To avoid confusion, smallpox inoculation

3920-645: The first human infection occurred in November or December 2019. Examination of the topology of the phylogenetic tree at the start of the pandemic also found high similarities between human isolates. As of 21 August 2021, 3,422 SARS‑CoV‑2 genomes, belonging to 19 strains, sampled on all continents except Antarctica were publicly available. On 11 February 2020, the International Committee on Taxonomy of Viruses announced that according to existing rules that compute hierarchical relationships among coronaviruses based on five conserved sequences of nucleic acids,

4000-547: The first infection, but the mechanisms that could account for this are not known. No natural reservoir for SARS-CoV-2 has been identified. Prior to the emergence of SARS-CoV-2 as a pathogen infecting humans, there had been two previous zoonosis -based coronavirus epidemics, those caused by SARS-CoV-1 and MERS-CoV . The first known infections from SARS‑CoV‑2 were discovered in Wuhan, China. The original source of viral transmission to humans remains unclear, as does whether

4080-404: The following two days as a precautionary measure due to a staff member from Fox Lane Middle School being placed under self-quarantine while awaiting testing for the coronavirus . It was later announced on March 13 that the school district would remain closed through April 3 which was later extended until the end of the 2020 school year. The district resumed hybrid instruction at the beginning of

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4160-559: The form of monoclonal antibodies (MAb). Passive transfer is used prophylactically in the case of immunodeficiency diseases, such as hypogammaglobulinemia . It is also used in the treatment of several types of acute infection, and to treat poisoning . Immunity derived from passive immunization lasts for only a short period of time, and there is also a potential risk for hypersensitivity reactions, and serum sickness , especially from gamma globulin of non-human origin. The artificial induction of passive immunity has been used for over

4240-477: The gut. Live attenuated polio and some typhoid and cholera vaccines are given orally in order to produce immunity based in the bowel . Hybrid immunity is the combination of natural immunity and artificial immunity. Studies of hybrid-immune people found that their blood was better able to neutralize the Beta and other variants of SARS-CoV-2 than never-infected, vaccinated people. Moreover, on 29 October 2021,

4320-567: The host immune response, mediated by antigen-specific lymphocytes . Unlike the innate immunity, the acquired immunity is highly specific to a particular pathogen, including the development of immunological memory . Like the innate system, the acquired system includes both humoral immunity components and cell-mediated immunity components. Adaptive immunity can be acquired either 'naturally' (by infection) or 'artificially' (through deliberate actions such as vaccination). Adaptive immunity can also be classified as 'active' or 'passive'. Active immunity

4400-423: The immune system create a dynamic biological environment where "health" can be seen as a physical state where the self is immunologically spared, and what is foreign is inflammatorily and immunologically eliminated. "Disease" can arise when what is foreign cannot be eliminated or what is self is not spared. Innate immunity, also known as native immunity, is a semi-specific and widely distributed form of immunity. It

4480-617: The much larger clades . Several different clade nomenclatures have been proposed. Nextstrain divides the variants into five clades (19A, 19B, 20A, 20B, and 20C), while GISAID divides them into seven (L, O, V, S, G, GH, and GR). Several notable variants of SARS-CoV-2 emerged in late 2020. The World Health Organization has currently declared five variants of concern , which are as follows: Other notable variants include 6 other WHO-designated variants under investigation and Cluster 5 , which emerged among mink in Denmark and resulted in

4560-627: The natural reservoir of the virus that caused the 2002–2004 SARS outbreak has resulted in the discovery of many SARS-like bat coronaviruses , most originating in horseshoe bats . The closest match by far, published in Nature (journal) in February 2022, were viruses BANAL-52 (96.8% resemblance to SARS‑CoV‑2), BANAL-103 and BANAL-236, collected in three different species of bats in Feuang , Laos. An earlier source published in February 2020 identified

4640-530: The original SARS-CoV . Like the SARS-related coronavirus implicated in the 2003 SARS outbreak, SARS‑CoV‑2 is a member of the subgenus Sarbecovirus ( beta-CoV lineage B). Coronaviruses undergo frequent recombination. The mechanism of recombination in unsegmented RNA viruses such as SARS-CoV-2 is generally by copy-choice replication, in which gene material switches from one RNA template molecule to another during replication. The SARS-CoV-2 RNA sequence

4720-1819: The pandemic. Coronavirus genomes and subgenomes encode six open reading frames (ORFs). In October 2020, researchers discovered a possible overlapping gene named ORF3d , in the SARS‑CoV‑2 genome . It is unknown if the protein produced by ORF3d has any function, but it provokes a strong immune response. ORF3d has been identified before, in a variant of coronavirus that infects pangolins . A phylogenetic tree based on whole-genome sequences of SARS-CoV-2 and related coronaviruses is: ( Bat ) Rc-o319 , 81% to SARS-CoV-2, Rhinolophus cornutus , Iwate , Japan Bat SL-ZXC21 , 88% to SARS-CoV-2, Rhinolophus pusillus , Zhoushan , Zhejiang Bat SL-ZC45 , 88% to SARS-CoV-2, Rhinolophus pusillus , Zhoushan, Zhejiang Pangolin SARSr-CoV-GX, 85.3% to SARS-CoV-2, Manis javanica , smuggled from Southeast Asia Pangolin SARSr-CoV-GD, 90.1% to SARS-CoV-2, Manis javanica , smuggled from Southeast Asia Bat RshSTT182, 92.6% to SARS-CoV-2, Rhinolophus shameli , Steung Treng , Cambodia Bat RshSTT200, 92.6% to SARS-CoV-2, Rhinolophus shameli , Steung Treng, Cambodia (Bat) RacCS203 , 91.5% to SARS-CoV-2, Rhinolophus acuminatus , Chachoengsao , Thailand (Bat) RmYN02 , 93.3% to SARS-CoV-2, Rhinolophus malayanus , Mengla , Yunnan (Bat) RpYN06 , 94.4% to SARS-CoV-2, Rhinolophus pusillus , Xishuangbanna , Yunnan (Bat) RaTG13 , 96.1% to SARS-CoV-2, Rhinolophus affinis , Mojiang , Yunnan (Bat) BANAL-52 , 96.8% to SARS-CoV-2, Rhinolophus malayanus , Vientiane , Laos SARS-CoV-2 SARS-CoV-1 , 79% to SARS-CoV-2 There are many thousands of variants of SARS-CoV-2, which can be grouped into

4800-522: The purpose of complying with the Americans With Disabilities Act, roof replacements and other structural renovations identified as necessary in the course of a years-long study. Allocations will also be made towards roofing replacements at Bedford Hills Elementary School, Bedford Village Elementary School and Pound Ridge Elementary School. On March 11, 2020, BCSD officials announced the entire school district would be closed for

4880-502: The risk of subsequent infection, including in the setting of increased circulation of more infectious variants. ..." Immunity is determined genetically. Genomes in humans and animals encode the antibodies and numerous other immune response genes. While many of these genes are generally required for active and passive immune responses (see sections above), there are also many genes that appear to be required for very specific immune responses. For instance, Tumor Necrosis Factor (TNF)

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4960-579: The role of pangolins as an intermediate host was initially posited (a study published in July 2020 suggested that pangolins are an intermediate host of SARS‑CoV‑2-like coronaviruses ), subsequent studies have not substantiated their contribution to the spillover. Evidence against this hypothesis includes the fact that pangolin virus samples are too distant to SARS-CoV-2: isolates obtained from pangolins seized in Guangdong were only 92% identical in sequence to

5040-428: The same pathogen later. A fetus naturally acquires passive immunity from its mother during pregnancy. Maternal passive immunity is antibody -mediated immunity. The mother's antibodies (MatAb) are passed through the placenta to the fetus by an FcRn receptor on placental cells. This occurs around the third month of gestation . IgG is the only antibody isotype that can pass through the placenta. Passive immunity

5120-509: The source of a majority of infections. That may explain how out of 217 on board a cruise liner that docked at Montevideo , only 24 of 128 who tested positive for viral RNA showed symptoms. Similarly, a study of ninety-four patients hospitalized in January and February 2020 estimated patients began shedding virus two to three days before symptoms appear and that "a substantial proportion of transmission probably occurred before first symptoms in

5200-558: The source. For a virus recently acquired through a cross-species transmission, rapid evolution is expected. The mutation rate estimated from early cases of SARS-CoV-2 was of 6.54 × 10 per site per year. Coronaviruses in general have high genetic plasticity , but SARS-CoV-2's viral evolution is slowed by the RNA proofreading capability of its replication machinery. For comparison, the viral mutation rate in vivo of SARS-CoV-2 has been found to be lower than that of influenza. Research into

5280-409: The term by referring to polio vaccine , measles vaccine etc. Passive immunity is the immunity acquired by the transfer of ready-made antibodies from one individual to another. Passive immunity can occur naturally, such as when maternal antibodies are transferred to the foetus through the placenta, and can also be induced artificially, when high levels of human (or horse ) antibodies specific for

5360-443: The transfer of "sensitized" or activated T-cells from one individual into another. It is rarely used in humans because it requires histocompatible (matched) donors, which are often difficult to find. In unmatched donors this type of transfer carries severe risks of graft versus host disease . It has, however, been used to treat certain diseases including some types of cancer and immunodeficiency . This type of transfer differs from

5440-498: The virus RaTG13 , collected in bats in Mojiang , Yunnan, China to be the closest to SARS‑CoV‑2, with 96.1% resemblance. None of the above are its direct ancestor. Bats are considered the most likely natural reservoir of SARS‑CoV‑2. Differences between the bat coronavirus and SARS‑CoV‑2 suggest that humans may have been infected via an intermediate host; although the source of introduction into humans remains unknown. Although

5520-550: The virus became pathogenic before or after the spillover event . Because many of the early infectees were workers at the Huanan Seafood Market , it has been suggested that the virus might have originated from the market. However, other research indicates that visitors may have introduced the virus to the market, which then facilitated rapid expansion of the infections. A March 2021 WHO-convened report stated that human spillover via an intermediate animal host

5600-484: The virus is infectious during the incubation period is uncertain, but research has indicated that the pharynx reaches peak viral load approximately four days after infection or in the first week of symptoms and declines thereafter. The duration of SARS-CoV-2 RNA shedding is generally between 3 and 46 days after symptom onset. A study by a team of researchers from the University of North Carolina found that

5680-587: The virus may be airborne as well, with aerosols potentially being able to transmit the virus. During human-to-human transmission, between 200 and 800 infectious SARS‑CoV‑2 virions are thought to initiate a new infection. If confirmed, aerosol transmission has biosafety implications because a major concern associated with the risk of working with emerging viruses in the laboratory is the generation of aerosols from various laboratory activities which are not immediately recognizable and may affect other scientific personnel. Indirect contact via contaminated surfaces

5760-422: The virus. Another case study described a 25-year-old man from Nevada who tested positive for SARS‑CoV‑2 on 18 April 2020 and on 5 June 2020 (separated by two negative tests). Since genomic analyses showed significant genetic differences between the SARS‑CoV‑2 variant sampled on those two dates, the case study authors determined this was a reinfection. The man's second infection was symptomatically more severe than

5840-421: The virus; some names used by different sources included "the coronavirus" or "Wuhan coronavirus". In January 2020, the World Health Organization (WHO) recommended "2019 novel coronavirus" (2019-nCoV) as the provisional name for the virus. This was in accordance with WHO's 2015 guidance against using geographical locations, animal species, or groups of people in disease and virus names. On 11 February 2020,

5920-516: The west in 1721 by lady Montagu" is quite not accurate and should be rendered "first promoted in the west, by lady Montague, in 1721". Because, as you can read here https://en.wikipedia.org/wiki/Variolation , the procedure was already known in Wales: "The method was first used in China, India, parts of Africa and the Middle East before it was introduced into England and North America in the 1720s in

6000-414: Was confirmed on 20 January 2020 during the COVID-19 pandemic . Transmission was initially assumed to occur primarily via respiratory droplets from coughs and sneezes within a range of about 1.8 metres (6 ft). Laser light scattering experiments suggest that speaking is an additional mode of transmission and a far-reaching one, indoors, with little air flow. Other studies have suggested that

6080-452: Was discharged on 15 April 2020 after two negative tests, and tested positive again on 15 August 2020 (142 days later), which was confirmed by whole-genome sequencing showing that the viral genomes between the episodes belong to different clades . The findings had the implications that herd immunity may not eliminate the virus if reinfection is not an uncommon occurrence and that vaccines may not be able to provide lifelong protection against

6160-460: Was exposed to the miasma in a swamp, in evening air, or breathing air in a sickroom or hospital ward, they could catch a disease. Since the 19th century, communicable diseases came to be viewed as being caused by germs/microbes. The modern word "immunity" derives from the Latin immunis, meaning exemption from military service, tax payments or other public services. The first scientist who developed

6240-417: Was increasingly referred to as variolation , and it became common practice to use this term without regard for chronology. The success and general acceptance of Jenner's procedure would later drive the general nature of vaccination developed by Pasteur and others towards the end of the 19th century. In 1891, Pasteur widened the definition of vaccine in honour of Jenner, and it then became essential to qualify

6320-496: Was suggested that the acquisition of the furin-cleavage site in the SARS-CoV-2 S protein was essential for zoonotic transfer to humans. The furin protease recognizes the canonical peptide sequence R X[ R / K ] R ↓X where the cleavage site is indicated by a down arrow and X is any amino acid . In SARS-CoV-2 the recognition site is formed by the incorporated 12 codon nucleotide sequence CCT CGG CGG GCA which corresponds to

6400-541: Was the most likely explanation, with direct spillover from bats next most likely. Introduction through the food supply chain and the Huanan Seafood Market was considered another possible, but less likely, explanation. An analysis in November 2021, however, said that the earliest-known case had been misidentified and that the preponderance of early cases linked to the Huanan Market argued for it being

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