There are two different kinds of spikes, each made of a different protein one is the hemagglutinin ha protein and the other is the neuraminidase na protein the ha protein allows the virus to stick to a cell, so that it can enter into a host cell and start. Nov 23, 2009 detect influenza type a viruses all subtypes in specimens from humans. Summary this is the 10th and final report for the 2019 2020 influenza season. Structure of influenza viruses, connected with influenza. While influenza a viruses infect humans and other animals, influenza b viruses affects only humans. Case reports successful explantation of a ventricular assist device following fulminant influenza type aassociated myocarditis paul c. In the northern hemisphere, the flu season can begin as early as october and can last as late as april or may. Infection with type b influenza is usually milder than with type a. These proteins are produced by alternative mrna splicing 64. These protocols have been shown to be widely effective for the identification of influenza type a viruses when used with the reagents and primers indicated. Structure of influenza viruses, connected with influenza life. Influenza type a viruses are categorized into subtypes based on the type of these two proteins on the surface of the viral envelope.
Members of the orthomyxoviridae family of segmented, negative sense, singlestranded rna viruses. The genome of influenza viruses is a linear, segmented and formed by ssrna. Influenza a h1n1 can cause a wide range of symptoms, including fever, cough, sore throat, body aches, headache, chills and fatigue. Who information for the molecular diagnosis of influenza. Flu can occur throughout the year but flu activity usually peaks in winter. Influenza a viruses can also cause sporadic infections or spread worldwide. As of week 392020, 164 917 influenza detections across the who european region had been reported. Influenza, also called the flu, is a viral disease that affects humans and many animals. A bad case of the flu can result in hospitalization or even death. Influenza a viruses are classified into subtypes based on two surface proteins, the hemagglutinin ha and neuraminidase na. Influenza type a is the primary group affecting both humans and animals. Till 2001, eight genome segments influenza a and b. Influenza virus type a excluding 1918 influenza a h1n1 strain and subtypes h5, h7 and h9.
Pdf successful explantation of a ventricular assist. Influenza d virus is 50% similar in amino acid composition to influenza c virus, similar to the level of divergence between types a and b, while types c and d have a much greater level of divergence from types a and b. Jun 02, 2009 influenza h5n1 viruses frequently cause primary viral pneumonia characterized by diffuse alveolar damage and interstitial fibrosis. Type a influenza is classified into subtypes depending on which versions of two different proteins are present on the surface of the virus. Select your audience and utilize these printable resources to help increase awareness with preventing the spread of influenza. Nonhuman viruses do not infect man but play an important role in the emergence of pandemic influenza by genetic reassortment with human viruses. In the current classification system, influenza a viruses are categorized into 16 hemagglutinin h and 9 neuraminidase n subtypes, although recently described bat influenza viruses may increase the number of hemagglutinin sub types. Nonhuman influenza viruses belong to type a whereas human influenza viruses belong to type a, b and c. Multiple influenza virus types and subtypes cause human infection, and currently circulating subtypes of influenza a virus include h1n1, h1n2, and h3n2. Jun 10, 2020 type a influenza is a contagious viral infection that can have lifethreatening complications if left untreated. Jan 10, 2020 influenza a is the only type that can cause a pandemic, which is a global spread of disease. Drift occurs in all three types of influenza virus a,b,c. How does influenza disproportionately impact older adults.
Both types can cause mild to severe illness in all age groups. Bird flu and swine flu pandemics both resulted from influenza a viruses. It can cause mild to severe illness, hospitalization, and even death. Antigenic differences exhibited by two of the internal structure proteins np and m, are used to divide influenza viruses into types a, b and c. Influenza, or flu, is a highly contagious respiratory illness caused by influenza viruses. Pdf influenza viruses are significant human respiratory pathogens that cause both seasonal, endemic infections and periodic, unpredictable pandemics. This global pandemic possibly infected 50% of the worlds population and up to 20% died. Criteria to distinguish a new case from previous reports not applicable. Mar 28, 2020 influenza a and b are the two types of influenza that cause epidemic seasonal infections nearly every year. For instance, during most of the 19971998 influenza season, a. A virus that has a type 1 ha and type 2 na, for example, would have the subtype h1n2. Influenza a viruses cause most human and all avian influenza infections. Influenza type a viruses are very similar in structure to influenza viruses types b, c, and d. Strains of influenza viruses are described by their type, host, place of first isolation, strain number if any, year of isolation and subtype.
Avian influenza has high mortality rate, as high as 60% 23456 hence it is a mayor concern if it mutates and can spread from human to human. Between 1918 and 1919 flu is thought to have killed over 50 million people 6 times as many as died as a consequence of the world war i. Pdf avian influenza type a virus infections has been classified by the office international epizootica oie as the most dangerous human and animal. There are 18 known ha subtypes and 11 known na subtypes.
The eighth segment of type a influenza virus encodes two proteins, known as nonstructural proteins ns1 and ns2 63. The core nucleoproteins are used to distinguish the 3 types of influenza viruses. The risk for exposure to influenza during travel depends somewhat on the time of year and destination. In naming virus strains, influenza virus type a, b, or c, host if other than humans swine, equine, chicken. Pdf the influenza virus iv is still of great importance as it poses an immanent threat to humans and animals.
Influenza a viruses are divided into subtypes on the basis of two proteins on the surface of the virus. Influenza virus a and b cause seasonal epidemics whereas influenza type c causes mild respiratory illness. Influenza is caused by infection of the respiratory tract with influenza viruses, rna viruses of the orthomyxovirus genus. Adjusted vaccine effectiveness against medically attended influenza by age group, us flu ve network, 201819. Yearly epidemics are typically caused by the influenza type a, with a smaller number of infections resulting from type b. Influenza viruses a, b, c, and d represent the four antigenic types of influenza viruses. These viruses are also called type a influenza viruses. Compared with past influenza seasons, this season there was a lower percentage of outpatient visits for influenza like illness, lower rates.
The influenza viruses are members of the family orthomyxoviridae. Small ernumbers of influenza a h3n2 and influenza b viruses were also identified. Primary viral pneumonia occurs mostly in individuals at high risk for influenza complications e. As any type of influenza it is fatal for immune compromised individuals. Influenza disease alabama department of public health. Two types of influenza, a and b, cause outbreaks in people. Taubenberger, md, phd,e alysia carboni, crnp, msn,b carol twomey, crnp, msn,b and evan loh, mdb we report a case of fulminant myocarditis. Comments this is a generic case definition for novel influenza infection.
Influenza flu is a contagious respiratory illness that can cause mild to severe illness. Flu influenza disease directory travelers health cdc. Influenza chapter 4 2020 yellow book travelers health. Influenza a can be found in many species, including humans, birds, and pigs. Influenza a is the most virulent type and is commonly associated with human disease. There are three groups of influenza viruses, called type a, b, or c.
In the temperate regions of the southern hemisphere, influenza activity typically occurs during april september. Influenza d viruses primarily affect cattle and are not known to infect or cause illness in people. Major outbreaks of influenza are associated with influenza virus types a or b. It most commonly causes a fever and respiratory problems. Anyone can get flu and it strikes suddenly and can last several days.
The virus particle also called the virion is 80120 nanometers in diameter such that the smallest virions adopt an elliptical shape. Wild aquatic birds particularly certain wild ducks, geese, swans, gulls, shorebirds and terns are the natural hosts for most influenza type a viruses. This mechanism changes a lowly pathogenic into a highly pathogenic avian influenza virus and has been associated so far only with subtype h5 and h7 viruses. Mcgovern, md,a susan chambers, crnp, msn,b emily a. Of the four antigenic types, influenza a virus is the most severe, influenza b virus is less severe but can still cause outbreaks, and influenza c virus is usually only associated with minor symptoms. Influenza a symptoms can be confused with signs of other conditions but are usually. Questions and answers immunization action coalition. Pdf avian influenza type ah5n1 epidemiological model. Structure of influenza virion influenza virions fig. Successful explantation of a ventricular assist device following fulminant influenza type aassociated myocarditis.
Dec 15, 2019 influenza is an acute viral respiratory infection that causes significant morbidity and mortality worldwide. There are 16 subtypes of ha and 9 subtypes of na known, but only h 1, 2 and 3, and n 1 and 2 are commonly found in humans. Influenza a h1n1 can cause a wide range of symptoms, including fever, cough, sore. Influenza pandemics are caused by type a viruses, and therefore these are the most feared type of influenza virus. Influenza a h1n1, previously referred to as swine flu is a respiratory disease, and is caused by a type a influenza virus. Influenza type c infections generally cause mild illness and are not thought to cause human flu epidemics. Influenza a viruses are divided into subtypes based on two proteins on the surface of the virus. Clinical illness follows a short incubation period and presentation ranges from asymptomatic to fulminant, depending on the characteristics of both the virus and the individual host.
In the temperate regions of the southern hemisphere, influenza activity typically occurs. The length of each particle varies considerably, owing to the fact that influenza is pleomorphic, and can be in excess of many tens of micrometers, producing. Influenza a viruses also have many different subtypes. Influenza is an acute respiratory illness, caused by influenza a, b, and c viruses, that occurs in local outbreaks or seasonal epidemics. Influenza virus has a rounded shape although it can be elongated or irregularly shaped and has a layer of spikes on the outside. There are three large groupings or types of seasonal influenza viruses, labeled a, b, and c. There are two main types of influenza virus that cause infection in humans types a and b and many sub t ypes or strains. Nov 18, 2019 influenza type c infections generally cause mild illness and are not thought to cause human flu epidemics. Subtypes of type a influenza virus are identified by two. Dec 11, 2020 yearly epidemics are typically caused by the influenza type a, with a smaller number of infections resulting from type b. Virus and disease, epidemics and pandemics steinhoff. Influenza viruses are enveloped, negativesense, singlestranded rna viruses of the family orthomyxoviridae.
Seasonal influenza causes substantial mortality and morbidity in the united states, with approximately 365,000 hospitalizations and 50,000 deaths per year 8, 9. Influenzaviruses c and d were estimated to have diverged from a single ancestor over 1,500 years ago, around 482 ad. Older adults and those with certain health conditions, are at high risk of serious flu complications. Influenza is a viral infection that attacks your respiratory system your nose, throat and lungs.
Pdf successful explantation of a ventricular assist device. Influenza flu is a contagious respiratory illness caused by. It was caused by an unusually pathogenic strain of influenza a virus. These cdc influenza printable materials include messaging to address flu recommendations to all types of audiences. Covid19, influenza, and rsv clinical diagnostic laboratory.
35 1015 376 585 1218 990 388 1080 233 1032 714 1447 68 828 915 1641 426 766 1113 1025 1866