What is antigenic shift in viruses?
What is antigenic shift in viruses?
The other type of change is called “antigenic shift.” Antigenic shift is an abrupt, major change in an influenza A virus, resulting in new HA and/or new HA and NA proteins in influenza viruses that infect humans. Shift can result in a new influenza A subtype in humans.
What is antigenic drift or genetic drift )?
Antigenic drift, random genetic mutation of an infectious agent resulting in minor changes in proteins called antigens, which stimulate the production of antibodies by the immune systems of humans and animals. These mutations typically produce antigens to which only part of a population may be immune.
Does antigenic shift only occur in influenza viruses?
Antigenic shift or reassortment variations occur only in influenza A viruses, which are sudden and complete changes in one or both surface antigens. This results completely in new viruses having surface antigens different from the antigens of the old viruses circulating in the population.
What viruses have antigenic drift?
Antigenic drift occurs in both influenza A and influenza B viruses. (Confusion can arise with two very similar terms, antigenic shift and genetic drift. Antigenic shift is a closely related process; it refers to more dramatic changes in the virus’s surface proteins.
What viruses go through antigenic drift?
What is an example of antigenic shift?
An example of a pandemic resulting from antigenic shift was the 1918-19 outbreak of Spanish Influenza. This strain was originally the H1N1 avian flu, however antigenic shift allowed the viral infection to jump from pigs to humans, resulting in a large pandemic which killed over 40 million people.
How is antigenic drift beneficial for viruses?
Antigenic drift is the accidental alteration of genes encoding antigens. It typically occurs in viruses and enables the pathogen to evade the immune system, triggering an infection once more.
When does antigenic drift occur in a virus?
Antigenic drift happens slowly over time and is common for most flu viruses; antigenic shift happens quicker but is not as commonly done. First let’s explain antigenic drift.
How is antigenic drift a public health concern?
Antigenic drift may also allow a virus to cross the species barrier to a new host. Of greater public health concern is the process of antigenic shift – also called reassortment – through which at least two different viruses combine, resulting in exchange of the HA (for example H3 replaced by H5) and consequently the formation of a mosaic virus.
How often does antigenic shift occur in the flu?
When shift happens, most people have little or no immunity against the new virus. While influenza viruses change all the time due to antigenic drift, antigenic shift happens less frequently. Influenza pandemics occur very rarely; there have been four pandemics in the past 100 years. For more information, see pandemic flu.
Which is the best example of antigenic shift?
Antigenic shift. The term is often applied specifically to influenza, as that is the best-known example, but the process is also known to occur with other viruses, such as visna virus in sheep. Antigenic shift is a specific case of reassortment or viral shift that confers a phenotypic change.