Q&A: Why last year's flu season was so bad

Florida Hospital Centra Care medical director explains breakout

ORLANDO, Fla. – The 2017-2018 flu season was one of the worst on record, according to reporting data from hospitals across the country.

Dr. Tim Hendrix, the medical director of Florida Hospital Centra Care, said the number of flu patients treated at their clinics was twice as bad as the previous worst season.

Why was last year so bad?

"It was because there was a change in the virus. We think that there was a mutation in the virus somewhere along the way, where the vaccine wasn't as effective, and the virus was more virulent," Hendrix said.

When did that mutation happen?

"Any time during the season. Because this is a rapidly multiplying spreading virus, there can be slight changes in the virus that's moving through the community, and it's hard to predict when that happens. Then we adjust for it next season, so last year there was maybe a slight change in the virus that made the vaccine not as effective, but going into this season, those adjustments have been made." 

Could you get one version of the flu at the beginning of the season and then a different version at the end? 

"I've seen people get the flu twice, and what happens is they get a type A early in the season, and then they get a type B virus that typically circulates at the end of the season," he said.

What if you already got the flu, should you still get the shot?

"Even if you get the flu, and you say, 'I already had the flu, I don't need to get my flu shot,' you still should get your flu shot. You don't know what's going to happen in the rest of the season," Hendrix said.

Can you get sick from the flu shot?

"You cannot get sick from a flu shot. What we're giving is what's called an inactivated virus; the inactivated flu virus means it's a killed virus that we're giving you to stimulate that immune response. That killed virus cannot cause an infection. Typically, the worst symptom is maybe a little soreness at the injection site, that is it."

Is the flu virus different this year?

"There are multiple viruses out there that cause the flu: there's H1N1, there's H3N2 and there are several type Bs that float around. And so what we do, the medical establishment, the World Health Organization, looks at what is going to be the most common virus this season and tries to make a good prediction, an educated guess, at what we're going to see," he said.

Last year I got the flu shot, but still got sick. Should I get the vaccine this year?

"If you get the flu and you've had your shot earlier in the season, the symptoms won't be as severe," Hendrix said. "It's a very important point, there is still protection with the flu shot."

Hendrix explained that predicting the flu depends on a lot of factors. Researchers look at data from the southern hemisphere where the flu season just wrapped up to make a prediction about the severity of the northern hemisphere's flu season ahead.

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