While the latest (week 45) FluView report from the United States continues to show only low levels of influenza activity across the country, yesterday we saw South Korea declare an early start to their flu season, and today we have the latest FluWatch report from Canada indicating an early arrival of flu activity as well.
Unlike our horrific H3N2 flu season last year - which saw 80,000 deaths in the United States alone - so far H1N1 seems to be the dominant flu strain this fall. While H1N1flu seasons tend to be milder than H3N2 years, this subtype does tend to exact a heavier toll on younger age groups.And while the flu season is just getting started in Canada, already they are reporting a significantly higher number of pediatric hospitalizations than usual, and early evidence suggests younger patients are being more affected than recent years.
FluWatch report: November 4, 2018 to November 10, 2018 (Week 45)
- Influenza activity continued to increase in week 45. The influenza season has started earlier than in recent years.The number of regions in Canada reporting sporadic or localized influenza activity in week 45 increased slightly compared to the previous week.
- Influenza A is the most common influenza virus circulating in Canada, and the majority of these viruses are A(H1N1)pdm09.
- The number of influenza-associated hospitalizations continued to increase in week 45. In particular, the number of pediatric hospitalizations is significantly higher than in recent years.
- The number of influenza outbreaks remains within expected levels. However, the settings in which outbreaks have been reported this season suggests that younger age-groups are being affected more than in previous seasons.
Laboratory Confirmed Influenza Detections
In week 45, the following results were reported from sentinel laboratories across Canada (Figure 2):(Continue . . . )
To date this season 1,523 laboratory-confirmed influenza detections have been reported (Figure 3):
- The percentage of tests positive for influenza continued to increase to 9.6% of tests positive.
- The percentage of tests positive for influenza A is higher for this time of year compared to the same period during the previous eight seasons. Laboratory detections of influenza have entered seasonal levels three weeks earlier than the median over the previous eight seasons.
- In week 45, 509 laboratory detections of influenza were reported, of which 97% were influenza A.
To date this season, detailed information on age and type/subtype has been received for 1,457 laboratory-confirmed influenza cases (Table 1):
- 97% have been influenza A
- Among the 922 influenza A viruses subtyped, 80% have been A(H1N1)pdm09
For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.
- Adults 20-44 years of age represent the largest proportion of cases (25%), followed by adults >65 years of age (20%).
The good news here, at least compared to last year, is that the H1N1 component of the flu vaccine is generally more effective than its protection against H3N2. And after two difficult H3N2 seasons, this year may prove more manageable.
But H1N1 is far from benign, and it tends to hit children and younger adults harder than H3N2.While flu activity is remains low in the United States, yesterday's FluView report does show the start of some activity, particularly in the deep south (see map below).
With the first big cold snap for the south land this week, a big winter storm in the northeast, and next week's Thanksgiving travel and intermixing, the conditions are ripe for flu to ramp up over the coming weeks.
If you haven't gotten your flu vaccine, now is the time to get it, as it takes a couple of weeks for the shot to take full effect.And whether you get the flu shot or not, now is also the time to start consistently practicing good flu hygiene (covering coughs, washing hands, staying home if you are sick, etc.).