Viral Mutation

[smellincoffee]

I'm a history student, but I like science and make an effort to maintain a well-rounded education. Tonight while reading on mutation in Richard Leakey's introduction to The Origin of Species, I wondered to myself how viruses like the influenza virus mutate to become resistant or immune to our vaccinations and so on. I made a few web searches, but turned up nothing useful. The only thing I found was this:

 

A virus is essentially a parasite: it enters a cell, hijacking its metabolic and reproductive machinery in order to replicate and to do this successfully it has to adapt to the creature it infects.

 

Most viruses do not mutate all that much N but the influenza, like the human immunodeficiency virus (HIV), is a notorious exception.

 

Flu viruses mutate in two ways

"Influenza viruses have an inherently high rate of mutation, which means that they are very flexible genetically and can adapt to a new environment," Maria Zambon, head of the flu laboratory at Britain's Health Protection Agency, said in an interview.

 

Flu viruses mutate in two ways: a slow, low-key change that usually is a minor public-health problem; and a fast, highly important genetic transformation which is the source of the alarm today.

 

 

Could someone elaborate?

[gonelli]

Vaccination is when a weakened or dead form of the virus is put into the body, which the body then recognises as "bad" and will create antibodies that help the body fight that particular virus.

 

So it isn't correct to say a virus becomes immune to vaccination, rather a new strain of the virus could infect a person and the body will not know straight away that this is a virus. Which results in the body needing more time before it can start fighting it with maximum effect. If the body has already incountered a particular virus before, it is a able to get rid of it faster, which is why a person may not get as sick or recovers quicker than if they wern't immune to the virus.

[CharonY]

The immune systems recognizes specific structures of the viruses (antigens, this term is not specific to viruses but to anything the immune system recognizes). If the genes for the given structures mutate, the resulting structure might be altered in a way that is not recognized by the immune system anymore.

[gonelli]

Is there a certain number of gene mutations that need to occur before the mutated virus can be classified as a different strain?

[CharonY]

Well, in the strictest sense a strain refers to genetically uniform entities. As such in theory a single mutation would be sufficient to classify it as a different strain. Note that this is not really a taxonomic distinction but rather is used for practical distinctions.

[smellincoffee]

The immune systems recognizes specific structures of the viruses (antigens, this term is not specific to viruses but to anything the immune system recognizes). If the genes for the given structures mutate, the resulting structure might be altered in a way that is not recognized by the immune system anymore.

 

Okay, thanks. I'm going to be reading a bit more on viral reproduction to sort out what happens where.