Almost 880,000 people could have been affected by an outbreak of the winter vomiting bug, according to health officials.
The Health Protection Agency (HPA) says the number of confirmed cases of norovirus is 83% higher than the same time last year,
So far this season, there have been 3,046 cases in England and Wales, compared to just 1,669 cases last season.
But for every reported case there are likely to be a further 288 unreported sufferers, warns the HPA.
The bug has swept the country and has led to the closure of dozens of hospital wards.
It has also affected holidaymakers on two P&O cruise ships, the Oriana and the Azura.
Norovirus is highly contagious and can be transmitted through contact with an infected person or contaminated surfaces and objects.
It is known to spread rapidly in closed environments such as hospitals, schools and nursing homes.
Symptoms include sudden vomiting, diarrhoea, or both, a temperature, headache and stomach cramps. The bug usually goes away within a few days.
Although people can suffer from norovirus at any time of the year, activity increases in the winter months, with most cases seen between January and March.
John Harris, a norovirus expert at the HPA, said: "The number of laboratory confirmed cases has risen again, following the drop in the number we reported last week.
"Norovirus is very contagious so we would urge anyone who thinks they may be unwell with norovirus to stay at home and stay away from hospitals and care homes.
"The infection is short-lived although it is very unpleasant while you are unwell. Most people will not need to go to see their doctor and will recover in a couple of days. It is important to take plenty of fluids to avoid dehydration."
A Department of Health spokesperson said the NHS was "well prepared" for the increase in health problems which are typical at this time of year.
The spokesperson added: "Our weekly published figures show the number of beds closed across the NHS due to norovirus symptoms is around 2%. This compares to 2.9% of beds that were closed during the peak of norovirus cases last winter."