Expert: Robert Baker - 3/24/2004

Question
I'm doing a grade 12 biology presentation and I'm trying to find out how viruses can remain dormant within their host wihout becoming active for long periods of time. Why and how do they do this? What causes viruses to become active again?
I would really appreciate links and references to studies if you could help out in that area.

Answer
Ben,

Lots of viruses can remain dormant in their hosts.  Probably the best examples are the herpes viruses, such as varicela zoster virus (VZV) which causes chicken pox.  If you got chicken pox as a kid, you are still infected with the virus, and will be for the rest of your life.

You have to remember that viruses are trying to survive and propagate themselves.  So, viruses will become dormant if conditions in the host are not right.  They will wait until conditions are better.  They do this by hiding their DNA or RNA in the cell and shutting down most of their gene expression.  It's the viral equivalent of a submarine running silent in order to escape detection.

The main influence on when  viruses become dormant and then reactivate is the host immune system.  If the host immune system is strong,  it will kill off viruses.  So viruses try to lay low and be stealthy - they go dormant.  Then, when stress or other illness causes the immune system to not work as well, the dormant virus can detect this and re-activate.

You can find a ton of good information out there on the web by doing a google search for 'viral latency' and maybe tacking on the term 'herpes' or 'hiv' etc.

Let me know if I can help any more!

Robert

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