Patients have been hit by a new strain of norovirus called ‘Sydney 2012’ and the current outbreak will continue until April, say experts at the Health Protection Agency (HPA).
HPA researchers carried out genetic testing of norovirus strains when the cases started to rise in October and found that a cocktail of different strains were circulating, including ‘Sydney 2012’ and ‘New Orleans 2009’, both named after the cities where they were first identified.
No strain was found to be more dominant, and officials added that Sydney 2012 does not cause more serious illness than the other strains of the illness, and can be managed in the same way – by washing hands thoroughly and regularly, especially after eating and going to the toilet.
Meanwhile HPA officials warn that although laboratory-confirmed cases of norovirus have dipped over the Christmas and New Year period, they expect to see the number of cases rising over the next few weeks and continue to rise until the beginning of April.
There have been 4,140 laboratory confirmed cases of norovirus this season, which begins in July for reporting reasons. The latest figures are 63% higher than the number of cases reported at the same point last year, when there were 2,535 cases.
Officials also estimate that for each confirmed case, there are a further 288 unreported cases.
Commenting on the new strain identified, Dr David Brown, director of the Virology Reference Department at the HPA said: ‘It is always difficult to predict the norovirus season and this year is no different.
‘Noroviruses mutate rapidly and new strains are constantly emerging. At the start of the season it is normal for outbreaks to be caused by a range of different strains. However as the season progresses particular strains are more successful and become dominant. The emergence of a new strain does not mean that it causes more serious illness and managing outbreaks and those will the illness remains the same.’
John Harris, an expert in norovirus from the HPA added: ‘Our latest figures covering the New Year period show a further decline in the number of cases and this is what we would expect to see. We can never predict how busy a season will be or what will happen in the weeks ahead although, as with other norovirus seasons we will expect to see an increase in the number of laboratory reports in the next few weeks until the end of March when activity begins to fall away.’