More than 140 wards in NHS hospitals have had to be closed as a result of an outbreak of norovirus – commonly known as winter vomiting bug.

The Daily Mail reports that as many as 500,000 people may have contracted the stomach bug so far. Some NHS trusts have banned visitors and cancelled operations in a bid to stop the infection spreading. Experts are concerned that, as everyday life resumes after the recent freezing weather, more people could contract the bug. Medics say that, for every case of norovirus in hospitals, there may be ‘hundreds more’ in the community.

Chairman of the Royal College of GPs, Dr Steve Field, said that the situation ‘seems incredibly serious’.

'We can only estimate the figures because most cases go unreported. We know it peaks twice a year and it looks like we are in the middle of a second serious peak – in a few months that could be affecting up to half-a-million people.’

Professor Hugh Pennington – Emeritus professor of microbiology at Aberdeen University –

said that, although this year seemed ‘very bad’ regarding outbreaks of winter vomiting flu, for most people affected, the illness would last for around two to four days only.

'Although it's very unpleasant, the vast majority will get better without any treatment. The worry is for the elderly and those with pre-existing health problems.’

Prof Pennington said that wards would need to be cleaned thoroughly, however, before patients were allowed back in, to prevent further infection.

The backlog of cancelled operations could also be made worse if doctors and nurses contract the virus.

This year’s outbreak was first seen in November and the current outbreak appears to represent a second wave, said experts.

The Department of Health said that the infection was not, however, a ‘superbug’ – and added that most people recovered from it.

'The NHS deals effectively with norovirus outbreaks all year round and this year is no different,’ said a spokesperson.

The Health Protection Agency said it was too soon for experts to be able to confirm whether a ‘sharp rise’ in cases of winter vomiting bug actually had occurred in January

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