Hospitals across the country are closing their doors to visitors because of outbreaks of the winter vomiting bug norovirus.
Birmingham City Hospital has asked visitors to stay away after closing four wards while at Maidstone Hospital in Kent three wards have closed to new admissions and visitors have been banned from all wards.
The George Eliot Hospital in Nuneaton has shut one ward, partially closed three and is turning away visitors. Five hospitals in Wales are also closed to visitors.
The number of cases of the winter vomiting bug is up 72% on this time last year, according to the Health Protection Agency (HPA).
This season 2,630 cases have been recorded - at the same time last year, just 1,533 had been noted.
However, the HPA admits that for every confirmed case there are likely to be a further 288 unreported sufferers, which means some 750,000 people could have been struck down by the bug across the country.
Norovirus is a highly contagious bug and spreads quickly in close environments such as hospitals and schools.
The symptoms include sudden vomiting and diarrhoea, which usually last for around two days.
Professor John Oxford, a biologist at Queen Mary's College and Chairman of the International Hygiene Council, said the best way to avoid the virus is to keep away from people who have it.
He told Sky News: "We don't really know why norovirus pops up its head at this time of year. All we know is that it does with some regularity more or less at the same time as influenza.
"It could be that the winter conditions drive us indoors, we are more close together and a virus like noro depends on closeness and also lack of hygiene.
"And I must say in the United Kingdom and around Europe there is a lack of hygiene that gives the virus an opportunity to start jumping from person to person."
John Harris, an expert in norovirus at the HPA, said: "People should be vigilant in their hygiene and we would like to remind anyone who has typical symptoms suggestive of norovirus infection to avoid visiting friends or relatives in hospital or care homes."
It comes as the P&O cruise ship Azura docked in Southampton carrying 3,059 passengers after an outbreak of the virus on board.
The ship had been on an 11-night cruise of the Iberian Peninsular. P&O confirmed there had been 10 cases and those passengers had been confined to their cabins to prevent its spread.
Some 300 people on one of the company's other ships, Oriana, were hit by the virus during a cruise earlier in the week.