Viruses and bivalve shellfish.

The epidemiological data clearly demonstrates that filter feeding bivalve shellfish can, and do, act as efficient vehicles for the transmission of enteric viruses transmitted by the faecal-oral route. This identified hazard has been documented as a cause for concern by various international agencies and has a long history. Disease outbreaks can occur on an epidemic scale as graphically illustrated by an outbreak of Hepatitis A in Shanghai, China in 1988 involving about 300,000 cases. Improvement of harvesting area water quality offers the most sustainable route to improvement in the virological quality of bivalve shellfish sold live. However there is growing awareness, and concern, that current regulatory standards based on faecal coliform monitoring do not fully protect the shellfish consumer from viral infection. New viral test methods based on PCR, and the development of alternative more reliable faecal pollution indicators, offer new approaches for the further development of public health controls. However, further work is required to build a scientific consensus and to understand the implications of their introduction into legislation.