Genetic slip

One understands by genetic slip the capacity of a Virus or a Génome with to transfer to give a new form, possibly more pathogenic than the preceding form, either because of intrinsic characteristics, or because the Immune system is not prepared to recognize the new virus, or for these two reasons.
the change can be done gradually over several years or decades, or brutally, by two different mechanisms:

In the case of the Virus has Bird influenza

One speaks about “ antigenic Glissement ” or “ drift transistor ” to describe one (or several) change (S) specific (S) of the viral genome. When these change S tiny relates to the Protéine S ha or Na, it did not require there to re-elect the sub-type of ha (H1 example) or Na (N1 example).
This type of small changes explains the epidemic S seasonal. It that which makes necessary a new Vaccin each year, is adapted to the dominant sub-types in circulation. the preceding one.

Brutal a change known as antigenic break or shift , can also occur, generally by exchanges of whole gene segments between one or more viral sub-types present in the same organization (human or animal).
Si this change produces the sufficiently new shape of protein ha and/or protein Na sufficiently different from those of the common viruses, the viral sub-type must be famous person in charge of Pandémie S.

This type of change is generally not viable or does not produce necessarily a more pathogenic virus, but it happens that such a mutant is particularly pathogenic vis-a-vis a Immune system which does not recognize them. It is them which are responsible for pandemias.

The antigenic break can come from the mixture of Gène S coming from an animal virus and a human virus .

It is supported by the segmentation of the ARN in 8 pieces in the case of the flu virus A.

Random links: