University outbreak of calicivirus infection mistakenly attributed to Shiga toxin-producing Escherichia coli O157:H7--Virginia, 2000.

On February 21-22, 2000, the Virginia Department of Health (VDH) was notified by a university student health center of two suspected cases of Escherichia coli O157:H7. At a local hospital laboratory, stool specimens from the two ill students tested positive for Shiga toxin-producing E. coli (STEC) using a commercially available enzyme immunoassay (EIA) kit. Further investigation revealed that the outbreak of gastrointestinal illness was caused by a Norwalk-like virus (NLV), a member of the calicivirus family. This report summarizes the outbreak investigation and laboratory findings used to identify the causative agent, and highlights the need for follow-up cultures on all specimens testing positive for STEC by EIA and for submission of isolates to state laboratories so that public health agencies can respond appropriately in identifying common source outbreaks.