A party of 57 people dined together in Hamamatsu City, Japan, in December, 2001. The next day, 22 of them developed diarrhea, vomiting, and fever. Four were confirmed to be infected with norovirus. One month later, four people from the same party developed hepatitis A. The group had eaten purple Washington clam (Saxidomus purpuratus) which had been imported from China and was subsequently lightly steamed with red pepper. The clams underwent subsequent viral examination. The genes for norovirus and hepatitis A were present. The hepatitis A strain isolated from the clam genetically matched the hepatitis A strain detected in the people. This food source caused two outbreaks.