All provinces and territories are reporting flu activity, the Public Health Agency of Canada said Friday.

The agency's weekly influenza report, published Friday, covering the period Dec. 1–7, showed activity across the country for the first time this season.

Flu, or influenza, is an infection of the nose, throat and lungs that spreads easily between people. It's caused by two types of viruses: influenza A and influenza B.

While the number of lab test results positive for flu continued to increase from the previous week, from 8 per cent to 9.1 per cent, this was below the average (13.7 per cent) for the same week in the past five flu seasons, the agency said.

Infectious disease experts say that while flu is unpredictable, Canada's season tends to occur in waves, typically starting in late fall and continuing until early spring.

To date this season, there have been 2,494 laboratory-confirmed cases of influenza.

Hospitalizations in children and adults

Provinces and territories have reported a total of 200 influenza-associated hospitalizations among adults, including 28 admissions to intensive care units and one death.

So far, PHAC said the percentage of tests positive for influenza B (4.0 per cent) is higher than the average (1.1 per cent) for this time of year. Influenza B can be particularly dangerous for children, pediatricians say.

In the latest report, PHAC said there were 24 lab-confirmed hospitalizations associated with pediatric flu cases — those age 16 and under. That's close to the average (22) for this week in previous seasons.

In the U.S., flu activity also continues to increase. The latest report from the U.S. Centers for Disease Control and Prevention has 23 states reporting widespread activity.

Experts in both countries say vaccination is the best way to prevent the flu and serious complications that can arise from it. It's not too late for anyone six months and older to get vaccinated.

Health officials also recommend not touching your face; washing your hands often; coughing and sneezing into the bend of your arm rather than your hands; and cleaning and disinfecting surfaces such as doorknobs and television remotes that many people may touch.