Dozens of hospital wards across the country have been forced to close because of outbreaks of a virulent stomach bug, NHS Trusts have said.
Cases of the norovirus among staff and patients have led to ward closures at dozens of hospitals.
Doctors estimate 100,000 people a week are catching the bug, which causes vomiting and diarrhoea and usually lasts around three days.
The virus is transmitted by contact with an infected person, by eating contaminated food or water or by contact with contaminated surfaces or objects.
Reported cases of the illness are at a five-year-high, but it is thought the real figure could be far higher, as many sufferers do not seek medical attention.
A spokeswoman for the Department of Health said she was unable to confirm the figures, which had come from individual health authorities.
Norovirus frequently causes outbreaks in places where people congregate, such as schools and cruise ships. Many cases also occur in hospitals and may cost the NHS more than £100 million a year during epidemics.
The Health Protection Agency (HPA) reported in December that the 2007 norovirus season had started "uncharacteristically early", with a greater number of cases nationally from the first week of November.
Norovirus is the most common cause of infectious gastroenteritis in England and Wales. The virus is easily transmitted by contact with an infected person, by consuming contaminated food or water or by contact with contaminated surfaces or objects.
According to the HPA, symptoms will begin about 12 to 48 hours after becoming infected and will usually last 12 to 60 hours. Most people make a full recovery within one or two days, however some (usually the very young or elderly) may become very dehydrated and require hospital treatment.