Notes from the field: Norovirus!
From the Centers for Disease Control and Prevention, and now making the CNN front page: notice of a new norovirus strain responsible for multiple outbreaks of gastrointestinal disease throughout the United States from September to December 2012. Norovirus is one of the leading causes of foodborne gastroenteritis, accounting for just about half of the foodborne illnesses reported to the CDC. This is the virus that is colloquially known as “stomach flu,” but it is completely unrelated to influenza virus, which enters the body via the respiratory route. The CDC estimates that roughly 21 million cases of norovirus-related gastroenteritis disease occur annually in the US, resulting in 70,000 hospitalizations and 800 deaths. Close to two thirds of the reported outbreaks occur in long-term care facilities, underscoring the significant problems that this virus raises for health care professionals. Desiree T, a student from the Spring 2012 BIO230 course, pointed out to me that February is National Norovirus Appreciation Month, so this seems as good a time as any to highlight the current outbreak.
An emergent strain of norovirus, designated GII.4 Sydney, was first identified in March 2012 in Australia. Over the next several months, the strain was observed to cause outbreaks worldwide. The CDC began noting case reports in the United States during the late summer and fall of 2012, and charted the origin of the reported outbreaks. Over 50% of the reported norovirus outbreaks during this period were due to GII.4 Sydney, and over half of those cases were due to direct person-to-person transmission. The CDC found that 61% of the cases were associated with long-term health care facilities, and restaurants were the second highest associated location, accounting for 19% of the cases.
The CDC notes that peak norovirus season is typically in late winter; consequently continued surveillance is necessary to determine the scope of the current outbreak. Point of contact hand antisepsis, environmental disinfection, and patient isolation continue to be the primary ways to prevent further transmission.