Flu season fizzles

MEGAN BASHAM, HOST: Coming up next on The World and Everything in It: the flu.

Last year, public health experts issued dire warnings about the possibility of a double pandemic: COVID-19 and influenza. Cases of the flu normally spike in the winter, and doctors worried patients needing hospital care would overwhelm the already strained medical system. But that didn’t happen.

MARY REICHARD, HOST: By this time last year, nearly 300,000 people had tested positive for the flu. This year, the CDC has logged fewer than 2,000 cases. So, what’s behind this record-breaking good news?

Joining us now to explain is Amesh Adalja. He is an expert in emerging infectious diseases at the Johns Hopkins University Center for Health Security. Good morning!

ADALJA: Good morning. Thank you for having me.

REICHARD: Well, let’s just start with the obvious connection between COVID-19 and the flu. Things like wearing masks, social distancing, and limiting mass gatherings do help prevent the spread of all kinds of sicknesses. So is that what helped to defeat the flu this year?

ADALJA: Yes, it likely was a combination of all of the social distancing, all of the mask wearing, all of the hand hygiene that basically made it very difficult for flu to spread. And you couple that to the fact that we have population immunity from prior flu seasons, as well as from prior flu vaccinations, and we had a pretty aggressive flu vaccine program this year. So there were a lot of things that made this season not very hospitable to influenza.

REICHARD: Well, this phenomenon isn’t unique to the United States. Nor is it unique to countries that had the strictest lockdown measures, even those with limited restrictions didn’t experience a normal flu season. So what other factors do you think might have been involved?

ADALJA: Well, I think it’s what I had mentioned. You have to remember that flu has more barriers to transmission than COVID-19 did. There is not a highly immune population. Flu has to deal with the fact that people got antibodies, that there are people that are vaccinated. And it just was something that was a barrier that was too hard for this virus to climb, but something that COVID-19 could easily climb over.

And I think that’s what we have to think about as we go back to normalcy that we’re kind of all anxious to see what happens to flu because it hasn’t circulated in the Northern Hemisphere, the Southern Hemisphere for about a year now. And that’s going to be interesting to see what does flu throw at us next. And I think it really just shows that there is value in some of this social distancing and masking that goes beyond COVID-19. And that may cause some people even when mask mandates are lifted to think about wearing masks when they’re in crowded and congregated places.

REICHARD: Some people have questioned whether cases diagnosed as COVID-19 might actually have been the flu. Do you think that’s possible?

ADALJA: Not really. I think what we’ve seen when we’ve looked for flu—and I’ve been a doctor that’s been taking care of patients throughout this pandemic—is almost every test we do for flu is negative. And in the midst of the flu season, when it was when we expected the flu season to occur, we were testing patients for both and flu tests were coming back negative. I think it’s likely the other way around—early in the pandemic that some people that they thought had influenza really had COVID-19. But now we’ve been looking for flu pretty aggressively and it’s just not there.

REICHARD: Well, in preparation for this flu season, this most recent one, health experts did urge everybody to get a flu shot anyway. Did that help?

ADALJA: I do think that the high level of vaccination with influenza this season and the public messaging did get a lot of people to get flu vaccinated. And that just erected another barrier for the flu virus that was really insurmountable for it this season.

REICHARD: Well, it’s good news that we had fewer cases of flu. But I wonder if there’s a downside. Do you think this will affect preparations for the next flu season?

ADALJA: Well, when we decide which strains of influenza to put into a vaccine, we look at the last season, we look at the other hemisphere, and we try to come up with our best estimate of what strains of the virus are going to circulate. So because there hasn’t been much circulation to flu for about a year, it becomes a much harder prospect to be able to come up with a match. So we may have a lot more uncertainty with the next version of the flu vaccine. And in terms of how well it’s going to match what circulates. So we could be in for a surprise in the next season, but we’ll have to wait and see.

REICHARD: Amesh Adalja is an expert in Infectious Diseases at Johns Hopkins University. Thanks so much for joining us today.

ADALJA: Thanks for having me.

Photo/iStock

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