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Question

Is it rare or common for some viruses to mutate or evolve into a much stronger one?
i mean, NOVA said its like putting 1000 chimpanzees on typewriters and one out of a thousand will type up shakespear's second act of hamlet

Answer 1

Hey I saw that NOVA show! IT was cool! I love NOVA! Anyways, think about it this way. A virus is asexual which means that it can split in two to make an exact copy of itself. Think about a million viruses all splitting and making another copy. Then youve got 2 mil viruses. Then 4 mil viruses. With so many reproductions sometimes there are genetic malfunctions just like a baby might be albino. And then the viruses might use this trait to their advantage because of evolution. Viruses accidentally mutate and sometimes cause them to be immune to a certain drug. I'd say there wil be one genetic mutation with every 5 million viruses asexually reproducing

Answer 2

Here is how viruses evolve. Mutations happen at random throughout the virus population (which is generally a very large population wherever they are present). Some vaccine comes along that will kill of 99.999% of a virus, but 0.001% have some mutation that makes them resistant to the vaccine, then that 0.001% is all that is left to reproduce and make the future generations of the virus. This means that they have a pretty good chance to pass on whatever mutation it was that allowed them to survive the vaccine. On the large scale, this means that future generations of the viruses will in general be immune to the vaccine since they come from the ones that survived the vaccine the first time. That is why vaccines change every year for things like the flu.

In general though viruses (or anything else really) will not evolve on their own unless their is some multi-generational pressure to do so (like a vaccine in the case of viruses).

About the chimp part of your question, I actually had to calculate something like that for a thermodynamics class. If we instead had 10 billion chimps and they each hit the keyboard 2 times per second and they had been doing this since the universe began (roughly 5.7 * 10^17 seconds ago). The probablility that ANY sequence of characters typed out is Hamlet is approximately 10^(-155,630). Not very likely. So, no, it is not like that.

Answer 3

First of all, viruses DO NOT split into two. Thats bacteria. Second of all, if in theory you started with 3 virus particles which produce 100 virus particles per generation and they replicate for only 4 generations you have 300 million viruses. Now if they replicate for even more generations you get more viruses than I care to count.
Thirdly, viruses work by hijacking a normal cells DNA replication hardware. And since the virus is really only interested in pumping out more virus it does not allow the cells normal DNA proofreading functions to work to their full extent. Hense mistakes/mutations are created in virus DNA.
Fourthly the most highly mutagenic viruses tend to be viruses such as influenza and the cold viruses which require dense human populations to be transmitted, hense creating even more viruses with chances to mutate.
So, all these factors and more mean that YES it is common for viruses to mutate.
Will they mutate stronger? Perhaps. They will generally evolve in the way to enhance their production. In theory this could make them weaker or stronger.

Answer 4

Let me conglomerate several of the very good technical answers above and add a bit. Yes, virus replicate their designs at massive rates, and if even a small percentage of one generation survive an auto-immune attack, it means that that percentage has some characteristic which allows them better survival in a harsh environment. The weak have been removed, which means these stronger sorts (relative to the environment) can reproduce at a good rate.
In any type of massive reproduction, man-made or natural, errors occur. For viruses this means that for the millions of the microscopic viruses that are reproducing there is a certain, realistic chance that a percentage of them can quite randomly be made to be immune to a body's natural defences. Natural selection by definition always selects the ones that are stronger, or more apt to survive in their environment. Unlike the thousand monkeys, virus infect in large numbers and replicate rapidly, producing scores of millions of individuals in a short period of time increasing the likelihood of a strong offspring.

Answer 5

It's common. Haven't you ever had the same cold or flu virus bounce from family member to family member and have the same family member get sick again? When a virus meets an antibody or something else that kills it, a few of the viruses survive and mutate into a strain that won't die as easily as the original virus. That's why they have such a hard time getting the right formula for the flu vaccine. Bacteria also mutate to become more resistant to antibiotics.

Answer 6

Let's say that you live in a part of africa and like to eat monkey meat. Monkey's are known to catch all kinds of viruses that humanoids (us, i.e. you and me) don't normally catch. (For instance, the simian aids virus.) But because most viruses mutate because they have to adapt to their surroundings, if you eat enough monkey meat, the virus may find a comfy human environment to set up shop. Look at bird flu, and the noted swine flu. Both are a virus that mutated from animals to humans.

By the way, if NOVA said that, shame on them.

Answer 7

Many viruses mutate at a rapid rate purposefully. Look at RNA viruses, and many of the polymerases used by viruses have a very high mutation rate in comparison to ours. It helps them adapt and evolve faster.

Oh no, I said evolve.

Answer 8

I was told that some cold virus gradually mutate in a slow phase at a rate that adult can built immunity to. This mutation usually take place in winter. So i think it's between rare and common.

Answer 9

It is rare, however because of the short lifespans of viruses, they tend to evolve at a much faster rate because there are new, more resilient generations being born all the time.

Answer 10

well its common for viruses to mutate often.. esp. the flu
but maybe its not exactly a stronger one.. just a different one that requires a different.. um antibiotic or whatever