(OT?) How Do Cold Viruses "Die"?

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Steven L. - 20 Dec 2004 00:01 GMT

I've often come across statements like "The common cold viruses can
survive on environmental surfaces for X hours...." Presumably after
that, it "dies".

But a virus isn't really "alive" in the sense of a cell that can
multiply on its own. It's just a strand of nucleic acid wrapped inside
a protein coat.

So how does a virus "die" in the environment? What happens to it? Does
it disintegrate, does the DNA strand break up? What is the process of
death for a virus look like?

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Scott Coutts - 20 Dec 2004 00:32 GMT

> I've often come across statements like "The common cold viruses can
> survive on environmental surfaces for X hours...." Presumably after
[quoted text clipped - 7 lines]
> it disintegrate, does the DNA strand break up? What is the process of
> death for a virus look like?

Yeah, the virus particle simply degrades eventually! When they say
'survive', what they really mean is 'retains infectivity'. So it
probably loses it's coat proteins as they dissociate, eventually the
proteins and the nucleic acids will degrade too, the same as they would
do with any other complex organic structure.

Cheers,

Scott.

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Fat Cat - 20 Dec 2004 01:40 GMT

I like this thread!

When large organic creatures decompose, it is bacterias doing their
work of decomposing. When bacterias decompose, virus does its
work.

Who will eventually decompose virus?

> > I've often come across statements like "The common cold viruses can
> > survive on environmental surfaces for X hours...." Presumably after
[quoted text clipped - 17 lines]
>
> Scott.

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Scott Coutts - 20 Dec 2004 02:06 GMT

Hi,

The viruses don't do any decomposition in the way that bacteria do...
sometimes they will cause the lysis of bacterial cells, but they dont
'decompose' the bacteria as a food source, as bacteria do with
substances in their surroundings. Viruses usually only damage bacterial
cells as a means of escape and release of the new viruses that have
replicated within.

Virus particles will break down the same way that other organic
molecules do. They could also be degraded by bacteria, because bacteria
secrete enzymes to break down material in their environment to use as a
food source (usually - that's a very simplified version). The bacteria
dont 'know' what it is that they're breaking down. For example, a
protease enzyme secreted by a bacterium will break down proteins - it
doesnt matter whether those proteins happen to come from a virus coat, a
dead animal, a leaf... it doesnt matter.

Otherwise, the virus particles might break down chemically, without the
help of bacterial enzymes, the same way that any other proteins and
nucleic acids will eventually break down.

Cheers,

Scott.

> I like this thread!
>
[quoted text clipped - 25 lines]
>>
>>Scott.

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Bob - 20 Dec 2004 03:46 GMT

>I've often come across statements like "The common cold viruses can
>survive on environmental surfaces for X hours...." Presumably after
[quoted text clipped - 7 lines]
>it disintegrate, does the DNA strand break up? What is the process of
>death for a virus look like?

As Scott noted, "die" in this context means to lose the ability to
infect.

How it occurs will vary with the virus. But many (most? but certainly
not all) viruses are unable to survive drying. The proteins of the
coat change shape (denature), and the virus is unable to properly
enter the cell and embark on its life cycle. I suspect that for many
viruses, it is some specific key protein that is damaged.

bob

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