A recent survey of oyster habitats found that 85 percent of oyster reefs have been lost due to disease and over-harvesting, and about 75 percent of wild oysters can now be found only in five locations in North America. Many of these mollusks are disappearing because of a new disease known as ostreid herpesvirus 1. The virus manifests only when water temperatures hit 61 degrees F, generating concerns that global warming will help it spread. OsHV-1 was first detected in Pacific oysters in France in 2008, and since then the virus has wiped out at least 20 percent of the oysters in French beds, and the disease has now spread to oysters in the United Kingdom. Because strains of herpes can infect a variety of mollusks, it’s possible that the virus could also infect clams, scallops and mussels. While people can’t catch herpes from an oyster, infected mollusks are still unsafe for consumption.