Patients at the Queen Alexandra Hospital, in Cosham, Portsmouth have been struck down with the Norovirus.
Visitors can only go to the virus-hit areas in 'exceptional circumstances' until the danger of the infection spreading passes.
Hospital bosses are calling on all members of the public to limit hospital visits while vulnerable people and children are asked to stay away altogether.
They say those who do visit should use hand cleansing gels at the entrances to the hospital and wards.
The areas affected are the Anne ward, which is completely shut to new admissions and visitors, while wards D2, D4, E1, F2 and F4 are also affected with restricted visiting.
Portsmouth Hospitals Trust spokesman Pat Forsyth said: 'Patients, relatives and visitors will be advised of the particular restrictions in each of these areas.
'People wishing to visit these wards should contact the ward prior to visiting. These restrictions will be applied to any other area where outbreaks occur.'
More information is available at www.porthosp.nhs.uk. Alternatively call (023) 9228 6000 ext 3270.