RELATIVES and friends of patients in Huddersfield hospitals are urged to stay away if they themselves are unwell.
Hospital chiefs want to avoid a repeat of the problems when Huddersfield Royal Infirmary was hit by a virus.
The Norwalk virus causes sickness and diarrhoea and has a major impact on hospital life.
Wards had to be closed and operations cancelled.
The Infirmary has been hit in the past by the bug.
Dr Howard Barnes, consultant in public health medicine for the Calderdale and Kirklees Health Protection Agency, said: "There is a great misconception that Norwalk (also called Norovirus) is hospital-acquired. But most often it is brought in by somebody.
"Although the Norwalk virus is relatively mild and symptoms short-lived, it can have a huge impact on hospital activities. That is why we want to reduce the risk as much as possible."
Dr Barnes added: "Large outbreaks can lead to ward and even hospital closure.
"It may mean that patients who were due to be discharged become too ill to be moved, those awaiting operations have treatment delayed and wards are closed to new admissions."
Norwalk can be spread in several ways, including in food and water, vomit, faeces and person-to-person.
Hospitals and GPs in the North are mounting a poster campaign to try to limit the spread of the illness this winter, when the bug is most prevalent.
The posters tell people not to visit friends and relatives in hospital if they are suffering from Norwalk and to wait at least 28 hours after the sickness and diarrhoea have gone before visiting again.
Most outbreaks occur in hospitals and residential and nursing homes during winter months.
In the first 10 months of last year there were 3,029 reports of the virus, compared with 1,064 during 2001. Neither did the number of cases last year fall in the summer, as is normal.
Symptoms of the Norwalk virus include diarrhoea and vomiting, nausea, abdominal cramps, headache, muscle pain chills and fever.
Symptoms last between one and three days. Recovery is usually rapid. All age groups can be affected.
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