常在菌っていうのがおもしろい

　⇒Harmless Virus May Be Deadly to Breast Cancer - Forbes.com

A common, harmless human virus can target and kill breast cancer stem cells, Canadian researchers report.
　
"We suspected that reovirus might be effective against cancer stem cells, because we have shown time and again how well it destroys regular cancer cells," Dr. Patrick Lee, a cancer researcher at Dalhousie Medical School in Halifax, Nova Scotia, said in a news release.

　もちろん簡単な善悪ということではないのだろうけど。