The herpes virus is carried by as many as 90% of people in most populations. The virus inserts itself into nerve structures in the human skin, where it stays for the entire lifetime of the carrier. Some people get regular coldsores, many people get just one, and the majority of people have no symptoms at all.

Scientists have now discovered that a viral protein called VP16 provokes herpes into causing visible coldsores. When this protein is created by a nerve cell that carries herpes, it causes the virus to make copies of itself, often resulting in visible signs of the virus: a coldsore, orally or genitally.

Herpes recurrences are usually associated with a fever, so in this study the scientists simulated high fever in mice. They found that VP16 was necessary for the virus to reactivate.

“Future studies will use this new information to develop strategies to prevent or control herpetic disease, said Dr. Sawtell, who also is an associate professor of Pediatrics at UC.”

Source: http://www.sciencedaily.com/releases/2009/03/090326215050.htm

Other news sources for this story:
http://www.genengnews.com/news/bnitem.aspx?name=51904776
http://health.usnews.com/articles/health/healthday/2009/03/27/treatment-target-for-herpes-pinpointed.html
http://www.eurekalert.org/pub_releases/2009-03/cchm-dop031909.php