The flu – in review

  | June 1, 2016

As flu seasons go, it could have been worse. This year's flu season kicked off in January, peaked in early March, and all but ran its course by the end of April, according to athenahealth's year-in-review analysis of the rates of “influenza-like illness" across the United States. Using patient data gathered from athenahealth's national provider network, researchers tracked the spread of flu in near-real time since last October.
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Here's a brief recap:

The flu shot is big

You know flu season is on the way when the number of people getting flu shots hits its peak. This season, that happened in mid-to-late October, when nearly 20 percent of outpatient visits to primary care physicians resulted in a flu vaccination.

This season hit late

The moment when flu rates actually start to rise varies from year to year. Likewise, the date of peak flu infection changes each season, although it always arrives between October and March and typically hits sometime in February.

This season, infection rates remained low through December and gradually gathered steam in the second week of January. From there, rates rose steadily for eight straight weeks before reaching a peak in early March. That made it the latest-breaking flu season of the last three years.

The West got it first

Regionally, patients in the West were the first to reach peak flu season — in late February. Patients in the Northeast, Midwest, and South saw their peaks a few weeks later, during the second week of March.

Kids get germs

At the height of the flu season, 3.4 percent of all outpatient visits to primary care providers were made by patients who exhibited flu symptoms. As is the case most years, pediatric patients had it worse than the population as a whole: the peak infection rate for children ages 0-17 was 6.6 percent.

Still, this year's flu season wasn't nearly as bad as last year's, when the peak infection rate was 6.2 percent for all visits, and 10.0 percent for pediatric visits.

Seniors weren't as sick

Similarly, seniors fared much better this year than last year, when they made up 8.3 percent of flu cases overall and had a 3.3 percent infection rate at season's peak. This year, patients 65 and older made up 4.8 percent of overall cases and had a 0.7 percent infection rate.

Vaccines make a difference

One likely explanation for the low infection rates across the board? An effective vaccine. According to the US Centers for Disease Control and Prevention, while last year's vaccine worked only 19 percent of the time, this season's vaccine had a 60 percent effectiveness rate. That's no consolation to anyone who got the flu, but it may be reason to be optimistic about next year.

Image credit: Sergey Panteleev/Getty Images

The flu – in review