![]() ![]() Antigenic drift occurs in all types of influenza including influenza A, B and C. To evolve and attack humans is just beginning to be appreciated.What is the Correct Way to Check Repeatability in Balances?Īntigenic shift is contrasted with antigenic drift, which is the natural mutation over time of known strains of influenza (or other things, in a more general sense) which may lead to a loss of immunity, or in vaccine mismatch. It is important to remember how many combinations of the 18 known hemagglutininsĪnd 11 neuraminidases have yet to be transferred to humans. So far, the number of victims have been small. Yet poorly transmitted, H5 and H7 type avian influenzas have recentlyīeen transferred to humans. Farm workers are at risk for contracting and transmitting the new reassorted viruses. Pigs are receptive to avian, human and swine influenza. An intermediate host is often required to modify the virus. Avian influenza is usually not effectively transmittedĭirectly to humans. ![]() Proximity allows for the greatest amount of cross infection and results in high Parts of the world where humans, pigs and poultry all live in close proximity. If the reassorted subtype is easily transferred among humans, thereīe no humans with antibodies to the new combination and a pandemic can occur. The HxN1 may be a novel combination created by reassortment of viral The result could be some H1N1 virus, some HxN1 virus, some HxNx. For example,Ĭell is infected by H1N1, and simultaneously infected with an avian HxNx, Viral RNA strand from one subtype is transferred to another. Each infected host will produce myriads of virion before it is killed or the infection is cleared by effective antibodies. Neuraminidase then triggers the sialic acid terminal to allow the new viral particles to escape the host cell. Once hemagglutinin binds to the sialic acid terminal of the receptor, the virus is brought into the cell for replication. Human and swine respiratory tract mucosa, as well as avian intestine, are all rich in hemagglutinin receptors. Hemagluttinin binds to a sialic acid terminal on the hemagluttinin receptor. Hemagglutinin is the viral surface protein responsible for binding the virus to susceptible cells. It is theorized that the H3 virus was suddenly able to infect humansĭue to what is called an "Antigenic Shift." However, in 1968, H3N2 caused a pandemic and remains a very common ![]() Prior to 1968, H3 type influenza was only known to infectīirds. The H1N1 to the H3N2 viruses, they can see that the viruses containĭifferent RNA and therefore produce different ( H and Pandemic "Hong Kong" flu was subtyped H3N2. The 1957 pandemic "Asian" flu was subtype H2N2, and the 1968 For example, the 1918 influenza A was subtyped as H1N1. Surface proteins, H and N, to differentiate between strains of Three types of hemagglutinin (H) and two types ofīeen involved in human influenza pandemics. Drift is one of the reasons we need to be re-vaccinatedĮighteen hemagglutinin and 11 neuraminidase subtypes are known to exist in nature (Kosik I., & Yewdell J.W. Consequently, the existing host antibodiesĪre unable to block infection. An altered configuration can render existing host antibodies lessĪble, or unable, to attach to the virus. Occurs, the configuration of the surface proteins, hemagglutinin or neuraminidase,Ĭan change. Occur during replication are known as "Antigenic Drift." As drift If such a change occurs in strand #4, the hemagglutinin protein These pointĬhanges can occur in any of the eight strands of viral RNA that make up influenzaĪ's genome. Involving an exchange of one amino acid for another are frequent. To replication errors than viruses which are based on DNA. ![]()
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