Some 40 people have been taken ill following an outbreak of the winter vomiting virus at Bedford Hospital.
The hospital has closed four wards, including the children's unit, to contain the virus, which causes non-fatal infections that last a few days.
Pregnant women, children and the elderly are particularly at risk from the infection, which causes projectile vomiting, dizziness and diarrhoea.
Dr Pat Nair, a consultant in communicable diseases at the hospital, advised vulnerable people to stay away from the hospital unless their condition was serious.
Full recovery
"If it's somebody with a milder illness who does not have to go into the hospital, who can be managed at home, then that is the right thing to do.
"You don't want to go into hospital and pick up another infection that you don't have," said Dr Nair.
There is no known treatment for the virus, which is also known as Norwalk.
However, it usually passes in 24 to 60 hours, and even very elderly patients usually make a full recovery.
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