Four wards at Mid Staffordshire Foundation Trust have been affected by norovirus.
Visiting has been limited and relatives have been asked to observe good hygiene practices when in the trust and to limit visitor numbers to two at a time.
The wards affected are Trauma & Orthopaedics, Acute Cardiac Unit, Acute Medical Unit and the GP Assessment Unit.
Not all of the affected wards are closed to admissions and discharges the trust has said.
Colin Ovington, director of nursing and midwifery said: “Ward staff are working with our infection control team to contain the norovirus within the areas affected.”