Grantham Hospital wards remain closed while hospitals in Lincoln and Boston are back to normal, says the United Lincolnshire Hospitals NHS Trust.
There will be no admissions on to wards at Grantham Hospital due to continuing cases of the winter vomiting bug, norovirus.
A&E will remain open, but any patients who need to be admitted to a ward will be diverted to other hospitals. Ambulance services will also take patients who need to be admitted for treatment to alternative hospitals.
Admissions at Lincoln County and Boston Pilgram hospitals have returned to normal.
The trust said staff have also been affected by the bug.