MadSci Network: Virology

Re: Lifespan of HIV in contact with air?

Area: Virology
Posted By: Samuel Conway, Senior Staff Chemist, Avid Therapeutics,Philadelphia, PA
Date: Wed Aug 13 21:39:18 1997
Area of science: Virology
ID: 869294717.Vi
I put all of your questions to my esteemed coworker, Dr. Robert King,
Biologist par excellence.  He responded thusly:

The lifespan of the virus is about 20 minutes, maximum, in a drop of
blood that lands on a surface outside the body.  Once that droplet dries,
the virus is dead.  No worries there.  The chances of you putting the
cut portion of your finger on a blood-smear that is fresh enough to contain
a sufficient amount of live virus to cause infection is infinitely small.

20 minutes also holds for body fluids on a toilet seat; this is from an
actual experiment.  In order to catch it, you would have to bring *broken*
skin into contact with the fluid.  The virus doesn't get sucked through
membranes just like that.  It needs to have some way into the blood stream.

And remember, once the virus particles are exposed to the air, they begin
to die.  After 20 minutes, there is effectively no live virus left.  And 
a dried smear, certainly, is not going to pose a very great danger.

Here is the bottom line:  Don't worry about borrowing books from the 
library.  Don't worry about going to the public restroom.  You need only 
worry if you intend to have unprotected sex with a person who has been 
exposed to the virus.  Minute tears and scrapes often occur in the skin
during various sex acts, and *these* are the routes through which the virus
is transmitted.

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