No matter what measures are taken, Denham said, oyster herpes is going to be tough to kick. Even if all the infected Pacific oysters are removed from oyster farms, wild Pacific oysters will still be present in surrounding waters, perhaps acting as “a reservoir for infection.”

It’s unlikely, though, that OsHV-1 μvar would end up in U.S. oyster beds, Renault said, because the United States doesn’t typically import oysters from Europe.

But a less virulent, herpes-like virus has been detected in farmed oysters off California. If sea temperatures continue to rise, he said, perhaps μvar or something like it could emerge in U.S. waters too.