The incurable, deadly virus is alarming fishing communities in Europe, where oyster herpes seems to be spreading — and could go on spreading as seas continue to warm, experts say. The virus has already killed between 20 to 100 percent of breeding Pacific oysters in some French beds in 2008, 2009, and 2010.
A new strain named Ostreid herpesvirus 1 (OsHV-1) μvar (mew-var), the virus remains dormant until water temperatures exceed 61 degrees, which U.K. waters reach in the height of summer, according to Kevin Denham of the British government's Fish Health Inspectorate.
Like the other strains of herpes that affect mollusks, OsHV-1 μvar attacks young oysters during breeding season, when the mollusks' bodies are so focused on producing sperm and eggs that the oysters have no energy to maintain an immune system, Renault said. But OsHV-1 μvar is "more virulent than strains we identified before," Renault said, adding that the virus is so efficient at killing its hosts that it can wipe out 80 percent of the oysters in a bed within a week.