An outbreak of a winter vomiting bug has led to the closure of 45 hospital wards in the last two weeks, health officials said.
The closures, which took place between November 12 and Sunday, occur when hospitals attempt to contain the extremely contagious infection.
Thousands of people have been struck down with a surge in norovirus, according to figures from the Health Protection Agency (HPA). Since July, the HPA has confirmed 1,975 cases in England and Wales - a 52% rise on the number of cases last year when it was 1,301 for the same period.
But the figure is likely to be much higher as many people do not report their illness to their GP.
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 October and April.
John Harris, an expert in norovirus at the HPA, said: "Outbreaks of norovirus in hospitals can be disruptive and often lead to ward closures. It is beneficial to try and limit the opportunities for the virus getting into hospitals in the first place. Everyone can help to minimise the risk of outbreaks at their local hospital by not going if they have the typical symptoms of a norovirus infection.
"These include a sudden onset of vomiting, which can be projectile in nature, and/or diarrhoea, which may be profuse and watery. People might also have other symptoms such as a temperature, headache and stomach cramps. The illness usually completely resolves in one or two days and there are no long-term effects. To reduce the risk of spreading the virus to other people, it is very important to wash your hands properly after you have used the toilet.
"If you are symptomatic, avoid preparing food until 48 hours after you have recovered. Over-the-counter medications can reduce some of the effects of the virus and more information is available online from NHS Direct, including a symptom checker."
A Department of Health spokeswoman said: "The NHS is well prepared for the increase in winter-related health problems which are typical at this time of year. Anyone who thinks they may have norovirus should avoid their doctor's surgery or A&E as this could spread the illness to vulnerable people and healthcare workers. Patients with symptoms should call NHS Direct or their local GP practice for advice.