Key Takeaways
- Flu cases in Canada reached a three-year high over the holidays but have since stabilized or decreased
- The dominant strain of influenza in Canada is the highly infectious and deadly H3N2 strain
- Cases of respiratory syncytial virus (RSV) and COVID-19 have risen since the last update
- Hospitalizations for all flu strains have remained stable, with 12.4 patients per 100,000 of the population reported per week
- Thirteen regions in five provinces have seen "widespread" influenza activity during the most recent reporting period
Introduction to the Flu Season
The latest national influenza data released by Health Canada shows that flu cases across the country reached a three-year high over the holidays but have since stabilized or decreased heading into the new year. The data, which accounts for the holiday period of December 14 to January 3, indicates that the percentage of positive tests for influenza reached 33.3 percent during the week of Christmas, the highest value recorded in the past three seasons. This high rate of positive tests is a cause for concern, as it suggests that the flu virus was highly prevalent during the holiday season.
Flu Activity and Trends
The following week, the rate of tests coming back positive for flu decreased to just over 27 percent, indicating a slight decline in flu activity. However, Health Canada notes that indicators of influenza activity were still high but were either stable or decreasing in the most recent week of data that ended January 3. The highly infectious and deadly H3N2 strain was found to be the predominant strain among influenza A cases detected in laboratory samples. This strain has been associated with severe illness and hospitalizations, particularly among older adults and young children.
RSV and COVID-19 Activity
In addition to flu, cases of respiratory syncytial virus (RSV) have risen since the last update on December 19, with 3.4 percent of tests returning positive. COVID-19 cases also rose to 5.3 percent positive tests. Health Canada notes that indicators of RSV activity continue to increase slowly, and some indicators of COVID-19 activity increased. This suggests that both RSV and COVID-19 are still circulating in the community and pose a risk to vulnerable populations, such as older adults and young children.
Hospitalizations and Outbreaks
Hospitalizations for all flu strains have remained stable since the last update on December 19, with 12.4 patients per 100,000 of the population reported per week. There were 343 reported outbreaks across the country in the most recent week of data, with 72 percent of which were related to influenza. The number of outbreaks marked the second week-over-week decline from a peak of 457 outbreaks reported during the week ending December 20. Thirteen regions in five provinces, including Alberta, Prince Edward Island, southern Ontario and Quebec, and British Columbia’s Lower Mainland, saw "widespread" influenza activity during the most recent reporting period.
Regional Flu Activity
The dominant strain being observed in Canada and the United States is the influenza A(H3N2) strain, including a subvariant — A(H3N2) subclade K — according to the World Health Organization. In Ottawa, three children between the ages of five and nine have died from influenza A-related complications, highlighting the severity of the flu season. The city’s health officials are urging anyone over the age of six months to get vaccinated to protect themselves and others from the flu. The Children’s Hospital of Eastern Ontario saw eight times more children test positive for influenza compared with the same month last year and double the number of children who needed to be hospitalized with the flu.
Prevention and Vaccination
The flu is a serious illness that can have severe consequences, particularly for vulnerable populations such as young children and older adults. Children under five are at a higher risk of severe illness from influenza because they have smaller airways, and their immune systems are still developing. Even healthy kids can become seriously ill, and the flu spreads quickly in schools and child-care settings. The best way to protect against the flu is to get vaccinated, and health officials are urging everyone over the age of six months to get vaccinated as soon as possible. By taking this simple step, individuals can help prevent the spread of the flu and protect themselves and others from serious illness.