Dorn VA Medical Center is asking anyone who has flu symptoms or has been exposed to the flu to refrain from visiting the veterans' facility in Columbia.
Veterans Affairs officials also said Thursday that they must restrict anyone under age 18 from visiting until the flu season is over.
The steps are meant to limit the spread of the seasonal flu, as well as the H1N1 swine flu.
VA officials say they must protect the health of those in the 172-bed hospital and its outpatient clinics, which see about 650 patients every day.
Children may be allowed to visit patients in the 10-bed hospice center, but this will be determined on a case-by-case basis.