Nanaimo General Hospital is dealing with a second serious infection outbreak since early April. (viha.ca)

Health officials have declared a hospital-wide norovirus outbreak at Nanaimo Regional General Hospital.

Twenty-two patients are showing symptoms, and the public has been asked to postpone visits, the Vancouver Island Health Authority says.

Norovirus outbreaks had already been declared on several units in the hospital, with four more people getting ill on Friday.

Officials say all of the new cases in the last week were caused by sick patients entering the Emergency Department and exposing others.

It's the second serious outbreak at the hospital in the past six weeks.

Two patients died in April from the bacterium C. difficile. At least 13 other patients were also infected with the deadly pathogen, which is often contracted during hospital stays.

Norovirus infection, which is highly contagious, can make people ill for one to three days and cause sudden episodes of nausea, vomiting and diarrhea.

There is no vaccine or medicine that can prevent the virus.