Table 1: Influenza Virus Testing Methods; Method 1 Types Detected Acceptable Specimens 2 Test Time CLIA Waived 3; Rapid Influenza Diagnostic Tests 4 (antigen detection): A and B: NP 5 swab, aspirate or wash, nasal swab, aspirate or wash, throat swab <15 min. [2][35], Influenza can be prevented or reduced in severity by post-exposure prophylaxis with the antiviral drugs oseltamivir, which can be taken orally by those at least three months old, and zanamivir, which can be inhaled by those above seven years of age. [45] During the 1918 pandemic, the respiratory route of transmission was clearly identified[23] and influenza was shown to be caused by a "filter passer", not a bacterium, but there remained a lack of agreement about influenza's cause for another decade and research on influenza declined. H17N10 and H18N11 are unable to reassort with other IAVs, but they are still able to replicate in other mammals. [19] Various mutations have been identified that are associated with AIVs adapting to mammals. [17] As of 2019, 18 H subtypes and 11 N subtypes have been identified. These bat viruses have HA and NA subtypes H17, H18, N10, and N11. Mayo Clinic; 2020. The influenza A H1N1 virus is a member of the family Orthomyxoviridae (a group of RNA viruses). We are a government-funded service, providing quality, approved health information and advice. [16], AIVs have occasionally infected humans through aerosols, fomites, and contaminated water. A newer category of drugs, the neuraminidase inhibitors, which includes oseltamivir (Tamiflu) and zanamivir (Relenza), was introduced in the late 1990s; these drugs inhibit both the influenza A and B viruses. Most A(H5) viruses identified worldwide in wild birds and poultry are LPAI, but occasionally HPAI A(H5) viruses have been detected. [1] From 1700 to 1889, influenza pandemics occurred about once every 5060 years. Grohskopf LA, et al. [1][9] Influenza-associated encephalopathy can occur directly from central nervous system infection from the presence of the virus in blood and presents as suddent onset of fever with convulsions, followed by rapid progression to coma. Please enter a suburb or postcode of your location and select from the list. [8][1], Influenza viruses comprise four species. Influenza A viruses are divided into subtypes on the basis of two proteins on the surface of the virus:hemagglutinin (HA) and neuraminidase (NA). However, there are multiple types of flu vaccines to choose from depending on your age, health conditions, and personal preferences. There are 18 known HA subtypes and 11 known NA subtypes. [33] Most flu vaccines are inactivated and administered via intramuscular injection. There are two main types of human flu viruses: types A and B. Most people who have flu are infected with the influenza type A virus. [17] In 1955, avian influenza was confirmed to be caused by IAV. Flu A viruses can be broken down into sub-types depending on the genes that make up the surface proteins. [1], Serological assays can be used to detect an antibody response to influenza after natural infection or vaccination. When discharging patients to care homes, it is important to take care if there is a known influenza outbreak. [21] Past pandemics, and especially the 1918 pandemic, are the subject of much research to understand flu pandemics. Factors that may increase your risk of developing the flu or its complications include: If you're young and healthy, the flu usually isn't serious. [22] The virion consists of each segment of the genome bound to nucleoproteins in separate ribonucleoprotein (RNP) complexes for each segment, all of which are surrounded by a lipid bilayer membrane called the viral envelope. Centers for Disease Control and Prevention. [59][60][61] The shortened form of the word, "(the) flu", is first attested in 1839 as flue with the spelling flu first attested in 1893. The number of deaths probably exceeded one million, mostly among the very young and very old. There is a copy of the RdRp, all subunits included, bound to each RNP. The polymerase snatches 5' caps for viral mRNA from cellular RNA to prime mRNA synthesis and the 3'-end of mRNA is polyadenylated at the end of transcription. You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance. All known subtypes of influenza A viruses can infect birds, except subtypes A(H17N10) and A(H18N11), which have only been found inbats. [8][1] Secondary S. aureus infection has been observed, primarily in children, to cause toxic shock syndrome after influenza, with hypotension, fever, and reddening and peeling of the skin. [15] In bacterial infections, early depletion of macrophages during influenza creates a favorable environment in the lungs for bacterial growth since these white blood cells are important in responding to bacterial infection. The novel betacoronavirus . Flu: What to do if you get sick. These two subtypes are included in the seasonal flu vaccine each year. Accessed Sept. 15, 2022. The exception are bat influenza-like viruses, which have an uncertain origin. In: Conn's Current Therapy 2022. [47], Initially, the microbial agent responsible for influenza was incorrently identified in 1892 by R. F. J. Pfeiffer as the bacteria species Haemophilus influenzae, which retains "influenza" in its name. All information these cookies collect is aggregated and therefore anonymous. [1] Direction transmission from wild birds is rare. There are three different virus types that are made distinct by their shape. The final genome segment encodes the viral nucleoprotein (NP). In the northern hemisphere, this is from October to May (more narrowly December to April[11]), and in the southern hemisphere, this is from May to October (more narrowly June to September[11]). Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. [1][9][10] ICV and IDV experience a slower rate of antigenic evolution than IAV and IBV. In particular, alveolar cell infection appears to drive severe symptoms since this results in impaired gas exchange and enables viruses to infect endothelial cells, which produce large quantities of pro-inflammatory cytokines. Only H subtypes H1-3 and N subtypes N1-2 are known to have circulated in humans,[17] the current IAV subtypes in circulation being H1N1 and H3N2. Kellerman RD, et al. Prevention Frequently Asked Questions Influenza, more commonly known as the flu, is a viral illness that affects millions of people every year. LPAI A(H6) virus outbreaks in birds are not internationally reportable, therefore, its true prevalence is unknown. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website. Notable HPAI viruses include HPAI H5N1 and HPAI H7N9. The sialidase activity of NA also cleaves any sialic acid residues from the viral surface, which helps prevent newly assembled viruses from aggregating near the cell surface and improving infectivity. https://www.cdc.gov/flu/season/faq-flu-season-2022-2023.htm. The several subtypes are labeled according to an H number (for the type of hemagglutinin) and an N number (for the type of neuraminidase ). [1] There is, however, an "original antigenic sin", in which the first HA subtype a person is exposed to influences the antibody-based immune response to future infections and vaccines. Some such as bacterial pneumonia can cause flu-like symptoms but are caused by bacteria. If you need to go back and make any changes, you can always do so by going to our Privacy Policy page. If you need to go back and make any changes, you can always do so by going to our Privacy Policy page. [17] Likewise, ICV primarily infects humans but has been observed in pigs, dogs, cattle, and dromedary camels. [1][32] Other NA inhibitors include laninamivir[1] and peramivir, the latter of which can be used as an alternative to oseltamivir for people who cannot tolerate or absorb it. The first human infections with A(H10N8) virus were reported in China in December 2013. DeeDee Stiepan: The flu vaccine won't protect against COVID-19 but it can help reduce the chance of getting the flu. [32] Among NATs, reverse transcription polymerase chain reaction (RT-PCR) is the most traditional and considered the gold standard for diagnosing influenza[39] because it is fast and can subtype IAV, but it is relatively expensive and more prone to false-positives than cultures. The envelope is reinforced structurally by matrix proteins on the interior that enclose the RNPs,[3] and the envelope contains HA and NA (or HEF[18]) proteins extending outward from the exterior surface of the envelope. Regulation of the type I interferon . While more than 100 different viruses can cause a cold, only influenza virus types A, B, and C cause the flu. [8], There is uncertainty about the use of masks since research thus far has not shown a significant reduction in seasonal influenza with mask usage. Influenza Surveillance Report (FluView), Previous Forecasts for the 2021-2022 Season, Tools to Prepare Your Practice for Flu Season, Information for Clinicians on Influenza Virus Testing, Multiplex Assays Authorized for Simultaneous Detection of Influenza Viruses and SARS-CoV-2, Information on Collection of Respiratory Specimens for Influenza Virus Testing, Information for Clinicians on Rapid Diagnostic Testing for Influenza, Information on Rapid Molecular Assays, RT-PCR, and other Molecular Assays for Diagnosis of Influenza Virus Infection, Algorithm: Interpreting Influenza Testing Results When Influenza is Circulating, Algorithm: Interpreting Influenza Testing Results When Influenza is NOT Circulating, Guide: Influenza Diagnostic Testing in Closed Setting Outbreaks, Guidance: Standard-Based Electronic Laboratory Reporting, Guidance: Antiviral and Obstetric Health Care, Guidance: Outbreak Management in Long-Term Care Facilities, Guidance: Use of Mask to Control Influenza Transmission, Guidance: Prevention & Control in Peri- and Postpartum Settings, U.S. Department of Health & Human Services. But children and adults at high risk may develop complications that may include: Pneumonia is one of the most serious complications. [47] By the time of the 1889 pandemic, which may have been caused by an H2N2 strain,[55] the flu had become an easily recognizable disease. Swine flu is mild in most people but can be severe for some high risk groups such as people with chronic conditions, pregnant people and Aboriginal or Torres Strait Islander people. As well as infecting people, the influenza A virus can infect animals, including birds and pigs. Symptoms include fever, headache, body aches, runny nose, sore throat, cough, and fatigue that come on quickly. Other mutations include mutations affecting which sialic acids NA proteins cleave and a mutation in the PB2 polymerase subunit that improves tolerance of lower temperatures in mammalian respiratory tracts and enhances RNP assembly by stabilizing NP and PB2 binding. There are four types of flu viruses, but the two that cause illness in humans most commonly are influenza A and influenza B. In 2009, a strain of flu virus known as H1N1 caused a respiratory infection in humans which spread rapidly around the world and became a pandemic. In the United States, no HPAI A(H7) virus infections have ever been reported in people; however, there have been four laboratory-confirmed cases of LPAI A(H7N2) virus infection in people. inactivated) viruses and live attenuated influenza vaccines (LAIVs) that contain weakened viruses. [8][9] Symptoms usually last for 28 days. The human influenza virus types A and B are responsible for the illnesses experienced during the flu season every year. In: Harrison's Principles of Internal Medicine. In many other animal species, avian influenza A viruses have been reported to cause occasional infections, but do not regularly spread among them (e.g., cats and seals). The most frequently identified A(H7) viruses associated with human infections are avian influenza A(H7N9) viruses, which were first detected inChina in 2013. information submitted for this request. For adults, emergency symptoms can include: Emergency symptoms in children can include: There is a problem with Healthdirect Australia is not responsible for the content and advertising on the external website you are now entering. Most people diagnosed with bird flu have caught it from infected birds so far, there is no evidence that bird flu can pass from human to human. Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health. To provide you with the most relevant and helpful information, and understand which Some features, tools or interaction may not work correctly. People at higher risk of developing flu complications include: Although the annual influenza vaccine isn't 100% effective, it reduces the chances of having severe complications from infection. Flu (influenza) season is quickly approaching in the United States.Per the CDC 's recommendation, all individuals aged six-months and older should receive a flu vaccine each year - ideally in October - to protect themselves (and others) against the flu.. Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. In: Goldman-Cecil Medicine. Seasonal flu is the type of influenza that typically causes illness for just a few months out of the year. [39], New antiviral drugs are also in development due to the elimination of adamantines as viable drugs and concerns over oseltamivir resistance. Antiviral treatment is also recommended if a person is hospitalized with suspected influenza instead of waiting for test results to return and if symptoms are worsening. [1], Equine IAVs include H7N7 and two lineages[1] of H3N8. [2][66] mRNA vaccines to provide protection against influenza are also under research. [4] These drugs are only functional against IAV[32] but are no longer recommended for use because of widespread resistance to them among IAVs. Consequently, the commonly recommended methods of infection control are respiratory etiquette, hand hygiene, and mask wearing, which are inexpensive and easy to perform. Because of this antigenic stability, relatively few novel lineages emerge. Find out about COVID-19, COVID-19 vaccines, and Mayo Clinic patient and visitor updates. ICV-associated hospitalization most commonly occurs in children under the age of 3 and is frequently accompanied by co-infection with another virus or a bacterium, which may increase the severity of disease. This does not mean that cold weather causes the flu; rather, cool weather, by bringing people indoors, along with other changes , is a contributing factor. https://www.cdc.gov/flu/highrisk/index.htm. Centers for Disease Control and Prevention. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. [11], Other respiratory complications that may occur include sinusitis, bronchitis, bronchiolitis, excess fluid buildup in the lungs, and exacerbation of chronic bronchitis and asthma. [1], If live poultry markets are not closed, then "clean days" when unsold poultry is removed and facilities are disinfected and "no carry-over" policies to eliminate infectious material before new poultry arrive can be used to reduce the spread of influenza viruses. But antibody levels may decline over time. [54], From 1918 to 1920, the Spanish flu pandemic became the most devastating influenza pandemic and one of the deadliest pandemics in history. Cookies used to make website functionality more relevant to you. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html. [11] Ultimately, presence of large quantities of viral RNA in the cell triggers apoptosis, i.e. Influenza is commonly called the flu, but it's not the same as stomach "flu" viruses that cause diarrhea and vomiting. Fatigue and malaise may last for several weeks after recovery, and healthy adults may experience pulmonary abnormalities that can take several weeks to resolve. HA and HEF[18] proteins have a distinct "head" and "stalk" structure. Seasonal influenza epidemics caused by influenza A and B viruses result in 3 to 5 million severe cases and thousands of deaths . [16] A notable example of this was the reassortment of a swine, avian, and human influenza virus in 2009, resulting in a novel H1N1 strain that caused the 2009 flu pandemic. [1], Diagnosis based on symptoms is fairly accurate in otherwise healthy people during seasonal epidemics and should be suspected in cases of pneumonia, acute respiratory distress syndrome (ARDS), sepsis, or if encephalitis, myocarditis, or breaking down of muscle tissue occur. [17], During the Second World War, the US government worked on developing inactivated vaccines for influenza, resulting in the first influenza vaccine being licensed in 1945 in the United States. [39] Rapid influenza diagnostic tests (RIDTs) are a simple way of obtaining assay results, are low cost, and produce results quickly, at less than 30 minutes, so they are commonly used, but they can't distinguish between IAV and IBV or between IAV subtypes and are not as sensitive as nucleic-acid based tests. 40 milligrams (mg) dose for people at least 10 years old, This page was last edited on 27 October 2022, at 15:56. There are many subtypes of avian influenza viruses, but only some strains of five subtypes have been known to infect humans: H5N1, H7N3, H7N7, H7N9, and H9N2. [45] From this pandemic, influenza became associated with sudden outbreaks of febrile illness. [32] The role of genetics in influenza is not well researched,[1] but it may be a factor in influenza mortality. If you have influenza A, you will have some or all of these symptoms: Children may also have abdominal pain, nausea and vomiting. [11][32][4] Additionally, the earlier NA inhibitors are provided, the better the outcome,[4] though late administration can still be beneficial in severe cases. [4], In 1968, H3N2 was introduced into humans as a result of a reassortment between an avian H3N2 strain and an H2N2 strain that was circulating in humans. What is Influenza? To date, all known flu pandemics have been caused by IAVs, and they follow the same pattern of spreading from an origin point to the rest of the world over the course of multiple waves in a year. Five flu pandemics have occurred since 1900: the Spanish flu in 19181920, which was the most severe flu pandemic, the Asian flu in 1957, the Hong Kong flu in 1968, the Russian flu in 1977, and the swine flu pandemic in 2009. They are:[1][14], IAV is responsible for most cases of severe illness as well as seasonal epidemics and occasional pandemics. A small H5N1 outbreak in humans in Hong Kong occurred then,[30] and sporadic human cases have occurred since 1997, carrying a high case fatality rate. Learn more here about the development and quality assurance of healthdirect content. [8] Primarily in children, in severe cases the immune system may rarely dramatically overproduce white blood cells that release cytokines, causing severe inflammation. There are three types of flu viruses: A, B, and C. Type A and B cause the annual influenza epidemics that have up to 20% of the population sniffling,. These symptoms are usually accompanied by respiratory symptoms such as a dry cough, sore or dry throat, hoarse voice, and a stuffy or runny nose. The different subtypes and strains of influenza viruses are distinguished by the hemagglutinin and neuraminidase antigens they possess. In sows, pregnancy may be aborted. https://www.uptodate.com/contents/search. An exacerbated immune response, however, can harm the host organism through a cytokine storm. There are 11 N subtypes, ranging from N1 to N11. [1] Approximately 3040% of people hospitalized for influenza develop pneumonia, and about 5% of all severe pneumonia cases in hospitals are due to influenza, which is also the most common cause of ARDS in adults. [1][9][2] In tropical and subtropical regions, seasonality is more complex and appears to be affected by various climatic factors such as minimum temperature, hours of sunshine, maximum rainfall, and high humidity. Influenza is caused by three types of RNA viruses called influenza types A, B and C (considered different genera), which all belong to the family Orthomyxoviridae.The disease, colloquially called . Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data. [19] Depending on the level of pre-existing immunity in the population, novel influenza viruses can spread rapidly and cause pandemics with millions of deaths. Influenza A virus belongs to the family of Orthomyxoviridae. In some cases, these types of influenza can be passed on to humans. [45] Notably, the 1957 pandemic was the first flu pandemic to occur in the presence of a global surveillance system and laboratories able to study the novel influenza virus. Read more on Immunisation Coalition website, Read more on TGA Therapeutic Goods Administration website. There are two main types of human flu viruses: types A and B. However, LPAI A(H6) viruses have been identified in various species of wild waterfowl and domestic poultry in Eurasia and the Americas. During an outbreak of influenza in 1743 that started in Italy and spread throughout Europe, the word reached the English language and was anglicized in pronunciation. A message has been sent to your recipient's email address with a link Other AIVs have less commonly infected humans since the 1990s, including H5N6, H6N1, H7N2-4, H7N7, and H10N7-8,[15] and HPAI H subtypes such as H5N1-3, H5N5-6, and H5N8 have begun to spread throughout much of the world since the 2010s. Among IAV subtypes, H1N1 and H3N2 currently circulate in humans and are responsible for seasonal influenza. This year, the vaccine will be available as an injection and as a nasal spray. This content does not have an English version. Figure S1: Migratory DCs can transfer infectious virus to uninfected cells in the absence of TPCK-trypsin. AskMayoExpert. [1] Closure of live poultry markets appears to the most effective measure[15] and has shown to be effective at controlling the spread of H5N1, H7N9, and H9N2. ICV and IDV have seven genome segments that encode nine major proteins. Influenza A viruses are further categorized into subtypes based on the 2 major surface protein antigens . In humans, a sizeable antibody response occurs ~1 week after viral exposure. CDC twenty four seven. [1][9][13], Influenza can affect pregnancy, including causing smaller neonatal size, increased risk of premature birth, and an increased risk of child death shortly before or after birth. [50] In 1648, it was discovered that horses also experience influenza. At first, the flu may seem like a common cold with a runny nose, sneezing and sore throat. [23][45], A minor influenza pandemic occurred from 1847 to 1851 at the same time as the third cholera pandemic and was the first flu pandemic to occur with vital statistics being recorded, so influenza mortality was clearly recorded for the first time. The influenza viruses are known for periodically giving rise to pandemic outbreaks in humans. [11], Influenza is typically characterized by seasonal epidemics and sporadic pandemics. [53][54] Shope's research reinvigorated research on human influenza, and many advances in virology, serology, immunology, experimental animal models, vaccinology, and immunotherapy have since arisen from influenza research. Pregnant women are at an elevated risk, which increases by trimester[1] and lasts up to two weeks after childbirth. HPAI H7N9 emerged sometime in 2016 and has occasionally infected humans incidentally. Also known as influenza. ", "Novel Influenza D virus: Epidemiology, pathology, evolution and biological characteristics", "Influenza Virus Infection, Interferon Response, Viral Counter-Response, and Apoptosis", "Roles of the Non-Structural Proteins of Influenza A Virus", "Reviewing the History of Pandemic Influenza: Understanding Patterns of Emergence and Transmission", "Transmission routes of respiratory viruses among humans", "Inactivation of influenza A viruses in the environment and modes of transmission: a critical review", "Seasonality of Respiratory Viral Infections", "Evolution of Influenza A Virus by Mutation and Re-Assortment", "Role of hemagglutinin cleavage for the pathogenicity of influenza virus", "Influenza virus-related critical illness: prevention, diagnosis, treatment", "Protection of children against influenza: Emerging problems", "Cell culture-derived influenza vaccines in the severe 20172018 epidemic season: a step towards improved influenza vaccine effectiveness", "Physical interventions to interrupt or reduce the spread of respiratory viruses", "Effectiveness of personal protective measures in reducing pandemic influenza transmission: A systematic review and meta-analysis", "Current Approaches for Diagnosis of Influenza Virus Infections in Humans", "Kawasaki disease and influenza-new lessons from old associations", "Estimated Influenza Illnesses, Medical visits, Hospitalizations, and Deaths in the United States 20182019 influenza season", Centers for Disease Control and Prevention, "Up to 650 000 people die of respiratory diseases linked to seasonal flu each year", "2,500-year evolution of the term epidemic", "Eyewitness accounts of the 1510 influenza pandemic in Europe", "Discovery and characterization of the 1918 pandemic influenza virus in historical context", "Complete genomic sequence of human coronavirus OC43: molecular clock analysis suggests a relatively recent zoonotic coronavirus transmission event", "1918 Influenza: the mother of all pandemics", "A virus obtained from influenza patients", "The Spanish flu and the fiction literature", "Global Influenza Surveillance and Response System (GISRS)", "Universal influenza virus vaccines and therapeutic antibodies", "mRNA vaccines manufacturing: Challenges and bottlenecks", https://en.wikipedia.org/w/index.php?title=Influenza&oldid=1118543268, Influenza virus, magnified approximately 100,000 times. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease. Screening infants is important for the early detection, diagnosis, and treatment of certain conditions that may not have been discovered immediately at birth. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i.e., global epidemics of flu disease. [54] Highly pathogenic avian influenza was recognized in 1878[54] and was soon linked to transmission to humans. There are 18 different H subtypes in influenza A that run from influenza H1 to H18. Water treatment, indoor raising of animals, quarantining sick animals, vaccination, and biosecurity are the primary measures used. Pterostil With the prevalence of novel strains and drug-resistant influenza viruses, there is an urgent need to develop effective and low-toxicity anti-influenza therapeutics. The most common form of influenza, type A can spread from animals to humans and is known to cause pandemics. Influenza is commonly called the flu, but it's not the same as stomach "flu" viruses that cause diarrhea and vomiting. CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. [1] The first antiviral drug against influenza, amantadine, was approved for use in 1966, with additional antiviral drugs being used since the 1990s. Influenza, commonly known as " the flu ", is an infectious disease caused by influenza viruses. Influenza. You will be subject to the destination website's privacy policy when you follow the link. [1][9] Antigenic drift occurs in all influenza species but is slower in B than A and slowest in C and D.[18] Antigenic drift is a major cause of seasonal influenza,[23] and requires that flu vaccines be updated annually.
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