Sunday, November 29, 2009

H1N1 gradually fizzling out

On Friday, the Public Health Agency of Canada released fresh statistics on H1N1 activity in Canada.  The data is for the week ended November 21st, because there is a certain delay before data from hospitals across the country are received and compiled.

The new stats show that H1N1 activity continues to decline.  Since April 18, 2009, there have been a total of 280 deaths related to H1N1.  My deepest sympathies go out to the families that have been affected.  Yet, from a scientific perspective, that's not an alarming rate at all.  Experts estimate that the regular garden-variety flu kills about 4,000 Canadians each year.  So the fact that we've only had 280 deaths since April (7 months) is quite underwhelming.  It's not much.

The number of outbreaks of H1N1 has dropped off a cliff since the peak attained two weeks earlier (see first chart).  It seems very likely that we've past the peak of this bug.    

The second chart shows the percentage of patients visiting hospitals with flu-like symptoms that have tested positive for H1N1 (red line).  Again, the percentage is down from the previous week and sits at its lowest level in the past 3 weeks. 

More important, in my opinion is the trend in the actual number of people who are diagnosed with H1N1 each week. I'm surprised that the PHAC doesn't provide any chart for this data.  I've cobbled together the data from various tables on their site:

Number of people diagnosed with H1N1 each week (new cases)
  • Oct 24:   2,880
  • Oct 31:   4,802
  • Nov 7:    6,151
  • Nov 14:  6,007
  • Nov 21:  3,723
As you can see, there was a surge in early November, but the number of new cases has fallen dramatically in the most recent week.  

In summary, I continue to think that H1N1 was way overblown and over-hyped.  I seriously doubt that we'll reach 4,000 deaths over a full year, as we have in past years.  I'm not losing any sleep over it.

But wait!  This news just in:  apparently a cat has been infected with H1N1.  Don't ask me how a feline can catch a swine flu that mutated into a human virus, but that's what I heard.   I don't suppose we'll do a mass vaccination of cats.