# 5203
While the United Kingdom is dealing with a well publicized resurgence of the 2009 `swine’ H1N1 virus this year, North America been dealt a different viral hand; the new Perth H3N2 strain of flu.
The latest available Canadian FluWatch surveillance report (week 50 – ending December 18th) indicates:
- During week 50, all influenza surveillance indicators continue to increase, particularly in regions across the Prairies, Ontario and Quebec.
- The proportion of positive influenza specimens reported during week 50 has increased over last week with 565 specimens out of 3,577 (15.8%) testing positive of which 99% are influenza A and 1% influenza B. Of the positive influenza A tests subtyped, 91% are influenza A/H3N2
and 9% are pandemic H1N1 2009. - Worldwide, influenza activity is increasing in the northern hemisphere, in particular in the UK (England), with pandemic influenza A/H1N1 and B being the predominant circulating viruses. Outbreaks and severe cases, mainly in people aged <65 years, continue to be reported in the
UK.
Less glamorous, perhaps, than its swine-introduced cousin – the new Perth H3N2 strain is not to be underestimated.
Unlike the pandemic strain which shows a preference for younger adults and children, this H3 virus is perfectly content infecting those over the age of 65 – an age cohort far more likely to be hospitalized, or even die, when infected with influenza.
Historically, years where the H3 strain predominates produce a more severe flu season, with more fatalities, than do years when H1 viruses rule.
Since most of these fatalities occur in the elderly – many of which are attributed to other conditions (COPD, coronary, pneumonia, etc.) – the impact of `seasonal’ influenza is often underestimated by the public.
Although we won’t get an update from the Canadian Surveillance system until Friday (none was produced last week due to the Holidays), anecdotal news reports indicate that influenza levels continue to rise in parts of Canada.
One such story appears in Healthwatch.ca today, which suggests that Canada may be on track for a worse than average flu season.
Seasonal flu more dangerous, widespread in H1N1’s wake
January 4, 2011
While you ought to follow the link and read the article, the thrust of the report is that low uptake of vaccine this year after the publicly perceived `fizzle’ of the swine flu pandemic has left the population particularly vulnerable to the new strain of H3N2.
This year’s flu vaccine contains antigens for the 2009 H1N1 virus, the newly emerging Perth H3N2 strain, and the currently circulating Influenza B strain.
All in all, it appears to be a pretty good match this year.
Here in the United States, where influenza activity is slowly climbing, the H3N2 virus is also the most commonly detected Influenza A strain.
A few excerpts from the CDC’s Week 51 FluView Report:
2010-2011 Influenza Season Week 51 ending December 25, 2010
All data are preliminary and may change as more reports are received.
Synopsis:
During week 51 (December 19-25, 2010), influenza activity in the United States continued to increase.
- Of the 3,284 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division, 689 (21.0%) were positive for influenza.
- The proportion of deaths attributed to pneumonia and influenza (P&I) was at the epidemic threshold.
- One influenza-associated pediatric death was reported and was associated with Influenza A (H3) virus infection.
U.S. Virologic Surveillance:
Pneumonia and Influenza (P&I) Mortality Surveillance
During week 51, 7.5% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was at the epidemic threshold of 7.5% for week 51.
It is important to remember that these reports are trailing indicators. They reflect the severity and activity level of influenza one, two, or even three weeks ago.
With 3 or 4 months left to the flu season in the northern hemisphere, it isn’t too late to get that flu shot.
Since we’ve 3 strains of influenza co-circulating, it is entirely possible that we could see more than one peak of flu activity in some regions this year. The UK, now being hit hard by H1N1 could be visited by the new H3N2 strain in the spring.
Similarly, North America could see the H1N1 virus pick up later this year.
Influenza truly produces a dynamic, constantly changing, dangerous, unpredictable and fascinating global epidemic each year.
One that still holds many secrets, and that – for now - can best be understood, and quantified, only in retrospect.
