The Thunder Bay District Health Unit confirmed Friday that it was the Norovirus that caused an outbreak of gastrointestinal illness that affected dozens of people.

Maltese Grocery had shut down its catering operations temporarily after 85 people became sick after eating food at three events the company had catered the previous week. They've since resumed, but with additional precautions.

Senior Public Health Inspector Abby Mackie said clinical specimens submitted to a lab confirmed the Norovirus to be the source of the outbreak.

"It looks as if we're looking at a food handler that may have inadvertently transmitted the illness through food," Mackie said.

"People can be shedding Noro-like virus and not even know. So, it's really important to be very stringent with hand-washing, glove use and other cleaning and disinfecting."

Maltese Grocery is making some additional changes to its cleaning and hand-washing procedures, including the use of new chemicals and sanitizers.

"If people are hosting gatherings at their houses or going out into the community, extra caution with hand-washing is your only protection," Mackie added.

The owners of the company released a statement apologizing for the outbreak.

"We are very sorry for everyone who has been affected and we take full responsibility, " Lisa and Dave Maltese said, adding that they are "working with the Health Unit and have taken every precaution to ensure this does not happen again."

Mackie said the Health Unit is confident in those steps.

He added that the grocery store has been open for 80 years and has had "a great inspection track record."

Norovirus infections are characterized by a sudden onset of diarrhea and nausea. Symptoms usually last an average of 24 hours.

It can be transmitted from person to person via contaminated food or commonly-touched surfaces, such as door handles and light switches.