Here's why health officials are predicting a worse flu season than usual


Two children in Minnesota have died from what appears to have been the flu so far this winter – one infant and one teenager.

In southeast Minnesota, the Mayo Clinic Express Care and ER are busier than they've been in years, and area schools are "half empty" as the virus jumps from kid to kid, the Rochester Post-Bulletin reports.

Attached to all those reports have been warnings about a potentially bad flu season.

“It’s too early to say for sure that this will be a severe flu season, but Americans should be prepared,” said CDC director Tom Frieden, M.D., M.P.H., last week.

Here's why.

Different strains

There are three different types of the influenza virus, noted as either A, B or C.

Those types are broken down further based on how the virus is structured – that's where you see the numbers and letters combination such as H1N1.

All of those different types and subtypes and strains – plus unexpected genetic changes to those – mean the virus can take a number of different forms.

This year's strain is pesky

According to early numbers from the CDC, the type of flu that looks to be most dominant this winter is A H3N2.

A H3N2 has been troublesome in the recent past, with the CDC noting it usually results in more severe flu illnesses, hospitalizations, and deaths. The three winters with the highest mortality rate in the past decade (2012-2013, 2007-2008, and 2003-2004) all happened when A H3N2 was the main strain.

Historically however those years are characterized as only “moderately severe,” not worse.

There is also some concern about this year's strain and "drift variants" – basically, mutations to the virus.

The CDC says it's finding about half of the H3N2 viruses being analyzed have some sort of mutation, and have drifted from a standard model.

This year's vaccine and flu strain don't match perfectly

There are several different flu vaccinations for this winter (which the CDC details here), and they commonly protect against three different strains: A H1N1, A H3N2, and an influenza B virus. There is a vaccine that protects against another influenza B type, making it four altogether.

The types of strains in the vaccine are based on what experts expect to see that season, Vox explains.

A H3N2 is in there this year, and as we know, that strain appears to be more prevalent right now.

But because about half of those A H3N2 viruses have mutated in some way (as we talked about in the previous section), the flu vaccine's ability to protect someone from it may be lessened. What's in the vaccine and what's out in someone's body isn't a perfect match, essentially.

It doesn't mean the vaccine is useless, the CDC says – those with a vaccination who pick up one of the mutated strains may have a milder form of the illness than those without a vaccination. So the CDC is still strongly recommending people get vaccinated.

According to CNBC, doctors have "ample" supply of flu shots.

Next Up