Greedy Virus Helps Spread Disease

"Mine, all mine!" That's what the vaccinia virus seems to be saying after it invades a cell and prevents its companions from following suit. But the behavior is hardly selfish. Researchers have found that the strategy actually helps the virus spread, as it speeds the targeting of uninfected cells. This previously unknown mechanism may lead to new ways to combat viral infections.

http://news.sciencemag.org/sciencenow/2010/01/22-02.html