I was lunching with a couple of other family practitioners and we were all wondering what happened to the seasonal flu this year. We’d gone through February, the traditional peak month of the flu season, and the virus was (as the cliche goes) conspicuous by its absence.
Turned out we weren’t alone. An article in the Wall Street Journal (“The Flu Season that Fizzled“) wondered the same thing. For example: The University of Virginia’s health clinic usually sees about 130 students a week with flu this time of year. Now it’s 3-5 a week.
Flu has peaked in late February or early March in 20 of the past 26 flu seasons, said Lyn Finelli, the CDC’s chief of flu surveillance and outbreak response.
So why not this year? The answer is a shrug. No one knows for sure.
Maybe it’s all the raised consciousness about personal hygiene – the handwashing and coughing into one’s sleeve. I attended a mystery writers convention (Bouchercon) in the fall where the organizers had posted signs with caveats about handshaking and such. I found Lee Child standing near one so we jokingly bumped elbows instead of shaking hands.
Sometimes a pandemic virus bumps a seasonal flu off the grid. H1N1 doesn’t make the headlines anymore, but it’s taken its toll since it appeared last April: 57 million cases and nearly 12,000 deaths (mostly in the under-24 population). Compare that to a typical year when seasonal strikes about 25 million people and directly kills 8,000 (usually at the older end of the population curve).
Don’t write off H1N1 yet. Spring break may spark new waves of cases on campuses. But we shouldn’t see a spike like we saw in October. Barring a significant mutation in the virus, the 57 million people who survived H1N1 infection are immune, and 86 million were vaccinated. That’s a big pool of immunity.
Whatever the reason, we seem to have dodged the much-anticipated double-barreled blast of flu this year.
Current plans are to include H1N1 in the 2010-11 seasonal flu vaccine, which will further expand the immune pool. And the new target population for the vaccine is virtually everyone over 6 months of age.