Influenza A activity increasing in Canada with sporadic cases and some outbreaks

Canada’s latest FluWatch report indicates that detections of influenza have increased sharply since the beginning of April. From March 13, 2022 to April 16, 2022, 1,287 laboratory detections (1,283 influenza A, 4 influenza B) were reported across Canada, with the majority occurring in individuals under 45 years of age. The first 12 lab-confirmed influenza outbreaks of the season were also reported during this period. Six occurred in long-term care facilities, one in an acute care facility and five in other types of facilities where individuals congregate.1 To date, for the 2021/22 flu season (August 29, 2021 to April 16, 2022), only 1,842 influenza detections (1,722 influenza A, 120 influenza B) have been recorded. This figure is much lower than the norm for the past six pre-pandemic seasons, where an average of 43,627 influenza detections were reported by this point in the flu season.1 Read: Exploring common OTC myths: Zinc for acne? However, influenza activity has been increasing in recent weeks from an average of 40 lab-confirmed detections per week in March, to 492 detections during the week of April 10 through 16, 2022. During the April 10 through 16, 2022 period, 3.8% of tests for influenza were positive. A 5% positivity rate is the threshold that would signify the start of a seasonal influenza epidemic. Canada may reach this threshold in the coming weeks.1 Also concerning is the sharp increase in influenza-associated pediatric hospitalizations reported by the Immunization Monitoring Program Active (IMPACT) network, with 19 influenza-associated pediatric (≤ 16 years of age) hospitalizations during the week of April 10 through 16, 2022.1 “This late-season increase in (flu) cases is not unique to Canada; since early March, influenza activity has increased in both the United States and parts of Europe," noted Public Health Agency of Canada spokesperson. "One reason for the increase in cases may be due to the lifting of public health restrictions that were in place for the past two years in Canada and globally.”2 To date, 47 influenza viruses [45 A(H3N2) and 2 A(H1N1)] isolated in Canada have been tested for antiviral resistance and all were sensitive to oseltamivir and zanamivir.1 Is it COVID-19 or influenza? COVID-19 and influenza can have similar symptoms. Flu symptoms usually appear within one to four days of exposure and include the sudden appearance of fever, cough and muscle aches/pain. Other common symptoms include headache, chills, fatigue, loss of appetite, sore throat and runny or stuffy nose. Some individuals (particularly children) may also experience diarrhea, nausea and vomiting.3 As COVID-19 shares many of these symptoms, patients who start to develop any of these symptoms, should be counselled to follow the same precautions taken for COVID-19.3, 4 Read: Self-care myth or fact: Are carrots really good for eyesight? Patients should be advised that they can only confirm if they have the flu or COVID-19 by being tested. If they have symptoms of the flu and haven’t received a negative COVID-19 test, they should follow COVID-19 prevention measures to help keep others safe.4 Healthcare providers can display a poster that explains how multiple public health measures (e.g., vaccination, hand-washing, masking) can help stop both the flu and COVID-19. The poster is available for download.5 An update on the flu case trajectory in Canada will be available when the next FluWatch report is published on May 27, 2022.1 References 1. Government of Canada. FluWatch report: March 13, 2022 to April 16, 2022 (weeks 11-15).(accessed May 13, 2022). 2. D'Andrea A. Shut out from COVID-19, influenza appears to be making a comeback in Canada. Why? Global News, May 5, 2022. (accessed May 12, 2022). 3. Government of Canada. Flu (influenza): symptoms and treatment. (accessed May 12, 2022). 4. US Centers for Disease Control and prevention. Similarities and differences between flu and COVID-19. (accessed May 12, 2022). 5. Public Health Agency of Canada. Stop the spread of the flu and COVID-19. (accessed May 12, 2022).

Influenza A activity increasing in Canada with sporadic cases and some outbreaks

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