CDC: New strain attributed to 2012 norovirus outbreaks

CDC: New strain attributed to 2012 norovirus outbreaks

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CDC: New strain attributed to 2012 norovirus outbreaks

CDC. MMWR. 2013;62:55-56.

• January 25, 2013

A significant increase in the number of norovirus outbreaks in 2012 was caused by the GII.4 Sydney strain of the virus, according to a recent CDC report. GII.4 Sydney was first identified in Australia in March and was responsible for acute gastroenteritis outbreaks in multiple countries.

“GII.4 noroviruses remain the predominant cause of norovirus outbreaks, and the GII.4 Sydney strain appears to have replaced the previously predominant strain, GII.4 New Orleans,” researchers reported in an early release of Morbidity and Mortality Weekly Report.

In the United States, GII.4 Sydney spread rapidly across the country, causing an increasing number of norovirus outbreaks. From September to December, 141 (53%) of the 266 norovirus outbreaks reported to the CDC’s public health network CaliciNet were attributed to GII.4 Sydney.

GII.4 Sydney was associated with four (19%) of 21 outbreaks in September, 22 (46%) of 48 in October, 70 (58%) of 120 in November and 45 (58%) of 77 in December (P.01). More than half (51%) of these outbreaks resulted from direct person-to-person transmission, whereas 29 (20%) were foodborne and one outbreak was waterborne. The mode of transmission was unknown in 39 (28%) of the GII.4 Sydney-related outbreaks. Long-term care facilities (65%) and restaurants (13%) were the most frequently reported settings for the outbreaks.

According to the CDC, continued surveillance for norovirus outbreaks will allow a better assessment of the public health implications of the new strain.

“Proper hand hygiene, environmental disinfection, and isolation of ill persons remain the mainstays of norovirus prevention and control,” the researchers wrote.

Disclosure: The researchers report no relevant financial disclosures.

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