A ward has been closed to new patients and visitors told to stay away after a winter bug break-out at Wigan Infirmary.
Both staff and patients have gone down with the diarrhoea and vomiting infection gastoenteritis, health chiefs have reported.
They say the symptoms are most likely due to norovirus which is known to be active in the Wigan community at present.
Wightington Wigan and Leigh NHS Foundation Trust (WWL) says its Infection Prevention and Control team have recommended that one ward does not take new admissions as specimens obtained from patients have identified the presence of the virus.
A spokeswoman said: “WWL wishes to assure borough residents that all necessary precautions are in place to help contain the spread of the infection.
“Visitors are asked to not visit if they have any symptoms of diarrhoea and/or vomiting and we would politely request that the elderly or very young do not visit.”
Norovirus, also called the “winter vomiting bug”, can be very unpleasant, but usually goes away in about two days.
It is highly contagious and can be passed on by being in close proximity to an infected person, touching surfaces or objects that have the virus on them, then touching your mouth, or eating food that has been prepared or handled by someone with norovirus.
Washing your hands frequently with soap and water is the best way to stop it spreading.
But alcohol hand gels do not kill norovirus.
Other symptoms can include a raised temperature, headaches and aching limbs.
Sufferers are advised to stay off school or work until the symptoms have stopped for two days.