A surge in norovirus infections has caught Canada off guard, with provinces like Ontario and Alberta particularly hard-hit. According to the Public Health Agency of Canada (PHAC), the spike in cases in 2024 surpasses the typical levels observed over the past five years.

The spread of norovirus is occurring at a rate that healthcare experts did not anticipate, presenting a significant challenge across the country. This surge stands in stark contrast to the lower transmission rates of contagious illnesses seen during the COVID-19 pandemic, when reduced social interaction led to fewer cases.

The surge in norovirus infections is not limited to specific regions, as cases have also risen in British Columbia, Saskatchewan, Manitoba, New Brunswick and Newfoundland and Labrador.

“People are doing more social things and going on cruises and those kinds of exposures that are risks for getting norovirus… I think we’re still going to see some changes in how common viruses behave because of the three years that people were doing less and interacting less,” University Health Network Infectious Diseases Leadership Chair Susy Hota, told a Canadian news organisation.

Norovirus is known for its high contagiousness and is responsible for gastroenteritis, manifesting in symptoms including nausea, diarrhea, stomach pain and vomiting. Each year, approximately four million Canadians fall ill due to foodborne infections, with norovirus alone contributing to over 1 million.

Norovirus infections typically incubate for a period ranging from 12 to 72 hours, with symptoms usually emerging within 24 to 48 hours. While the infections are typically self-limiting and tend to be of mild to moderate severity, they onset suddenly and can present with symptoms such as nausea, vomiting, non-bloody diarrhea and abdominal pain.