Cambridge Memorial Hospital has declared a norovirus outbreak at its rehabilitation unit, the second such outbreak in a month. 

The hospital says visitation policy will be one visitor per patient until there are no new cases of the virus for five days.

Donna Lyle, a registered nurse and infectious disease practitioner at the hospital, says symptoms of norovirus include vomiting and diarrhea. The virus is common during winter months, she said.

"There are many nursing homes and retirement homes in outbreak right now," said Lyle.

The virus generally lasts 24 to 48 hours.