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What We Can Learn From The 1968 Hong Kong Flu Pandemic


1968 was a year of protests and social unrest. It was also the year of a strain of the flu that started in Hong Kong that spread and killed nearly a million people worldwide and 100,000 here in the United States. That specific strain still comes back during the flu season, though it's not as lethal. So what lessons can we take from that pandemic to move forward in this one about how COVID-19 will behave? Dr. Ed Belongia is an infectious disease epidemiologist with the Marshfield Clinic Research Institute in Wisconsin. He joins me now. Welcome.

ED BELONGIA: Thank you for having me.

GARCIA-NAVARRO: So can you first tell us why that strain of the flu, H3N2, became so deadly? What do we know about it?

BELONGIA: Well, H3N2 was a virus that never circulated in people before 1968, and the flu viruses are unusual in the sense that different viruses can recombine. And there are flu viruses that circulate in wild birds, many different types of flu viruses. And if those recombine with a human strain, that can lead to a new pandemic virus that people are not immune to. And that's what happened in 1968.

GARCIA-NAVARRO: How does the Hong Kong flu compare to COVID-19? I mean, do we know?

BELONGIA: What we did learn from from 1968 is that pandemic virus became a seasonal virus. It gradually became adapted more and more to be able to spread efficiently in humans, even in the presence of immunity because, of course, after the pandemic, then a lot of the population did, in fact, have some immunity to that strain. But it continued to cause seasonal infections because the immunity was not long-lasting and because the viruses continued to mutate. And even today, these viruses mutate faster than other flu strains. And that requires frequent updates to the flu vaccine strains.

GARCIA-NAVARRO: How likely is it going to be that that could happen with COVID-19, that we could get some kind of immunity but that it could come back seasonally?

BELONGIA: It will become seasonal, most likely, unless there's permanent immunity, but we don't really know if there's permanent immunity or not. And as more and more people become infected or hopefully get vaccinated and develop immunity, then we will see what sort of effects that has on the virus and whether or not we see any changes. But at this point, it's too early to really make any predictions, I think.

GARCIA-NAVARRO: What should we be looking out for in the fall when, potentially, there'll be flu and COVID-19 circulating?

BELONGIA: Some important similarities between COVID-19 and flu that will be important is that social distancing and mask use will serve a dual benefit by reducing the risk of both diseases. And in fact, there was just a study published from Taiwan where they found a substantial reduction in serious flu cases this past winter after they instituted a nationwide policy of mask use. And they believed that those two are related. And so we're hopeful that the same measures that are needed to control COVID-19 will also be beneficial in reducing the severity of the flu season.

And then I guess I would also just say that the one thing that we know for sure is that it will be possible to get a flu vaccine before you can get a COVID-19 vaccine. And it's very important this season for people to get a flu vaccine. It's more important now than ever because of the fact that we're going to be dealing with two very serious pathogens. If this is an H3N2 season, it will be more severe. We know that historically. And this year, the flu vaccine will have three new strains. And so in order to be protected against those new strains, we really encourage people to get the flu vaccine and get it as soon as possible in the fall so that they're protected from that. The last thing anybody needs is to get infected with both COVID and flu. And we can at least protect against one of those right now.

GARCIA-NAVARRO: Dr. Ed Belongia is an infectious disease epidemiologist with the Marshfield Clinic Research Institute. Thank you very much.

BELONGIA: Thank you, Lulu. Appreciate it.

(SOUNDBITE OF THRUPENCE'S "RINSE REPEAT") Transcript provided by NPR, Copyright NPR.