Recurring norovirus outbreaks in a long-term residential treatment facility - Oregon, 2007.

On November 9, 2007, the Oregon Public Health Division (OPHD) was notified of an outbreak of acute gastroenteritis in a long-term residential treatment facility. Two previous outbreaks caused by norovirus had occurred at the facility in March and July 2007. OPHD initiated an in-depth epidemiologic investigation, which included submitting archived and recent specimens from the three outbreaks to CDC for genotyping. This report summarizes findings of the outbreak investigation and laboratory testing. The overall attack rate for the most recent outbreak was approximately 14% among patients and 7% among employees. The outbreak was unusual in that it lasted 63 days, versus 24-27 days for the two previous outbreaks in 2007. Person-to-person transmission was suggested by a prolonged and dispersed epidemic curve and lack of illness in some wards, although all wards were served by one central kitchen. Barriers to conducting adequate hygiene (e.g., lack of handwashing stations) and multiple lapses in infection control (e.g., noncompliance with staff wellness policies) were identified. Timely and sustained implementation of comprehensive and effective infection control measures are needed to prevent and contain norovirus outbreaks in large institutional settings.