Australasian Science: Australia's authority on science since 1938

Gastro Epidemic Expected This Winter

By Stephen Luntz

A new strain of norovirus has all the aspects required to wreak havoc through Australian digestive systems this winter.

Prof Peter White of the University of NSW School of Biotechnology and Biomolecular Sciences identified the virus, dubbing it Sydney 2012. While there are many different strains of norovirus circulating in the community, only those of the GII.4 type are known to cause epidemics, let alone pandemics, which White attributes to their rapid rate of mutation.

White helped identify Sydney 2012 and noted its membership of the GII.4 class. “I knew straight away it was a potentially pandemic strain,” White says. Co-discoverer Dr John-Sebastian Eden says: “I noted it was quite different to what we’d seen before. It was a hybrid.”

Two strains combined to form Sydney 2012 when one unfortunate individual was infected by both simultaneously. White says the original combination probably occurred in 2006, but despite the virus’ virulence it took 6 years to become widespread in the community. Last year one-quarter of gastroviral cases in NSW were caused by Sydney 2012, and in New Zealand the figure was closer to 100%.

Sydney 2012 has been responsible for an epidemic in Europe, leading the English press to dub it the “chunder from Down Under”. White suspects that once the American medical system catches up on analysis it will be found responsible for the upsurge in cases there too.

Five norovirus pandemics have been recorded since 1996. White says there is debate about whether the same thing was happening before “but we lacked the tools to identify it, or if this is actually new”.

Another unresolved question is why gastrointestinal infections are so much more common in winter, with White favouring the view that the viruses simply last longer in cold conditions, creating more chance of transmission.

Immunity to Sydney 2012 is low in the community, and White says there is little an individual can do to prevent infection. Rather, once sick they should concentrate on not passing the virus on by “cleaning up their own vomit if possible” and not coming into work when ill.

“Also, remember that you are still shedding the virus after you feel better, so it is best to stay home for several days afterwards.”