Internationally Distributed Frozen Oyster Meat Causing Multiple Outbreaks of Norovirus Infection in Australia

Obligations to report outbreaks of foodborne disease under the International Health Regulations (2005)

Every year, Australia identifies 2–3 outbreaks associated with imported foods. To examine national authorities’ obligations under the International Health Regulations (2005), we reviewed outbreaks in 2001–2007 that implicated internationally distributed foods. Under these regulations, 6 (43%) of 14 outbreaks would have required notification to the World Health Organization.

Epidemics of gastroenteritis during 2006 were associated with the spread of norovirus GII.4 variants 2006a and 2006b

BACKGROUND

Acute gastroenteritis is commonly associated with norovirus genogroup II (GII) infection. Norovirus GII has 17 classified genotypes (GII.1-GII.17), but only 1 norovirus genotype (GII.4) is associated with global epidemics of gastroenteritis. In 2006, an increase in global norovirus activity was observed.

METHODS

During the period from December 2005 through August 2006, a total of 231 fecal samples were obtained from patients with acute gastroenteritis from Australia and New Zealand. Norovirus RNA was amplified and sequenced to determine norovirus genotype and relatedness to known epidemic norovirus GII.4 variants.

RESULTS

Two GII.4 variants, designated 2006a and 2006b, were identified in 61.8% and 11.3%, respectively, of the 186 cases investigated. Norovirus 2006a and 2006b have also been implicated as the predominant causes of norovirus-associated gastroenteritis across Europe in 2006.

CONCLUSIONS

The global increase in norovirus-associated gastroenteritis in 2006 was linked to the emergence of 2 novel GII.4 variants, 2006a and 2006b.