An electron microscopic image that shows SARS-CoV-2, the virus that causes COVID-19. (AFP)

A B.C. hospital has declared a "precautionary" COVID-19 outbreak after cases were confirmed in one of its units.

Northern Health posted a notice about the cases at University Hospital of Northern B.C. in Prince George on Wednesday. 

So far, two patients and four staff have tested positive for the disease in the internal medicine unit, but no evidence of ongoing transmission has been recorded. 

"Northern Health Public Health is closely monitoring for additional cases, and the facility is taking steps to protect the health of staff and those they care for, with enhanced outbreak precautions," the health authority said in a statement. 

Increased cleaning and symptom monitoring is underway. 

"The precautionary outbreak declaration will be in place until at least 14 days after any potential exposure to a lab-confirmed case," Northern Health's statement said. 

"If there is still no evidence of transmission of illness after that time, the outbreak can be declared over."

Several other hospitals in B.C. are dealing with active outbreaks including Langley Memorial Hospital, Surrey Memorial Hospital, Burnaby Hospital, Abbotsford Regional Hospital and Vancouver General Hospital.