Norovirus: new strain may be to blame for record cases say experts

 By Rebecca Smith, Medical Editor

The so-called Sydney 2012 strain has become the most common form of norovirus in circulation, scientists at the Health Protection Agency said.

The virus, named after the place it first emerged, caused a similar early start to the norovirus season in Australia as has happened here.

So far over 1.1m people have contracted nororvirus this winter in England as cases approached double the normal rate.

The disease eased slightly over Christmas and New Year but this is likely to be due to less testing being carried out over the holiday period and could rise again.

Norovirus strains do change slightly and several strains were in circulation at the beginning of the UK season but Sydney 2012 has now become dominant.

It does not cause more severe illness and there remains no effective treatment, only fluids and rest until it clears on its own, usually after 48 hours.

The new strain was documented in a research paper published in the journal Eurosurveillance.

The authors, from a number of different countries, said the strain was linked to higher cases globally and healthcare systems should prepare for a 'severe norovirus season'.

They said the data from England and Wales suggested there were more norovirus cases than normal and the higher rates were not simply due to the disease striking earlier.

Dr David Brown, Director of 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.

“There is no specific treatment for norovirus infection other than to let the illness take its course, with symptoms usually lasting around two days. Keeping hydrated is very important and you can take over-the-counter medicines to relieve headaches and aches and pains.”