Map of overall Influenza activity level by province and territory, Canada, Week 5
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Like the United States, Canada is reporting increasing levels of influenza across much of their nation, prompting recent headlines such as:
The latest FluWatch report from PHAC combines data from weeks 51 & 52.
- Influenza activity in Canada continues to rise with increases in all indicators in weeks 51 and 52
- A total of 4632 laboratory detections of influenza were reported, of which 97.7% were for influenza A viruses, predominantly A(H3N2)
- 127 new influenza outbreaks were reported, 87 of which were in long-term care facilities
- 114 new paediatric influenza-associated hospitalizations were reported through the IMPACT network, and 176 hospitalizations including 15 deaths among adults ≥20 years of age were reported through Aggregate surveillance
- The ILI consultation rate increased, but remains within the expected range for this time of year.
- Similar to previous years, older adults (persons aged ≥65 years) are the most affected this season; with 41.3% of laboratory detections to date, increased outbreaks in long-term care facilities, higher hospitalization rates and a high proportion of antiviral prescriptions among those ≥75 years.
As the following chart indicates, influenza detections are on the ascendant, and to a lesser extent, so are RSV (Respiratory Syncytial Virus) cases. Rhinovirus, coronavirus, parainfluenza, and metapneumovirus detections – in contrast - are on the decline.
A breakdown of influenza strains identified this year suggest that most are similar to the strains included in this year’s vaccine. That said, we won’t really know how effective this year’s vaccine has been until after the season is over.
Influenza strain characterizations
During the 2012-13 season, the National Microbiology Laboratory (NML) has antigenically characterized 177 influenza viruses [136 A(H3N2), 17 A(H1N1)pdm09 , and 24 influenza B].
The 136 influenza A(H3N2) viruses were antigenically similar to the vaccine strain A/Victoria/361/2011.
The 17 A(H1N1)pdm09 viruses were antigenically similar to the vaccine strain A/California/07/09. Among the influenza B viruses, 20 were antigenically similar to the vaccine strain B/Wisconsin/01/2010 (Yamagata lineage) and four were similar to B/Brisbane/60/2008 (Victoria lineage; component of the 2011-2012 seasonal influenza vaccine) (Figure 6).
Figure 6. Influenza strain characterizations, Canada, 2012-2013, N = 177
Note:The recommended components for the 2012-2013 Northern Hemisphere influenza vaccine include: an A/Victoria/361/2011 (H3N2)-like virus; an A/California/7/2009 (H1N1)pdm09-like virus; and a B/Wisconsin/1/2010-like virus.
For more detailed information on the flu, and what Canadians can do to protect themselves, Public Health Canada maintains a specialized influenza website called FightFlu.ca.
