Figure 1. A) Foodborne outbreaks reported to the Centers of Disease Control and Prevention (CDC), United States, 1991–2000. B) Norovirus (NoV)-confirmed foodborne outbreaks reported to CDC, United States, 1991–2000. REVB, Respiratory and Enteric Branch, CDC; RT-PCR, reverse transcription–polymerase chain reaction. Percentage value above bars represents proportion of all foodborne outbreaks reported to CDC that were laboratory-confirmed to be due to NoV by REVB and by some state public health laboratories.