Response and Mitigation of Large Norovirus Outbreak associated with Person-to-Person Transmission at the U.S. Air Force Academy, July 2011

When outbreaks of acute gastrointestinal illness occur in military or institutional settings, they can have significant impact on training and education. In July 2011, nearly 300 basic cadets, instructors, food service workers, and health care professionals were affected by a laboratory confirmed outbreak of Norovirus during field training exercises at the United States Air Force Academy. An epidemiological investigation suggested that the virus was most likely introduced by one or more food service workers through a fomite. After the initial spike in the cases, the outbreak was propagated via person-to-person transmission—which ultimately accounted for 70% of the cases. Several factors facilitated the spread of the virus including: close living quarters, poor personal hygiene, stress associated with the field training environment, and the use of contaminated communal bathrooms. Isolation of ill individuals as well as a comprehensive, coordinated education and sanitization campaign helped to limit the duration and scope of the outbreak. Although the attack rate was 22% for the 1085 trainees, the outbreak did not spread to the 3000+ returning cadets at the beginning of the academic year. Strict sanitation practices, proper personal hygiene, surveillance and early identification should be used to prevent an outbreak, isolation of ill individuals and appropriate disinfection procedures will limit the scope and duration of a Norovirus outbreak.