Dual Infections: When Coronavirus And Flu Virus Compete : Shots - Health News There's a lot that scientists don't know about how viral infections can interact. But researchers are eager to figure out how coronavirus infections might affect flu infections and vice versa.
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Flu Season Looms And Scientists Wonder How Flu And COVID-19 Might Mix

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Flu Season Looms And Scientists Wonder How Flu And COVID-19 Might Mix

Flu Season Looms And Scientists Wonder How Flu And COVID-19 Might Mix

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MARY LOUISE KELLY, HOST:

The flu season will soon be upon us. It usually starts in late fall. This year, it is coming as the U.S. continues to grapple with another serious respiratory virus. NPR's Nell Greenfieldboyce looked into what it could mean to get the flu plus COVID-19.

NELL GREENFIELDBOYCE, BYLINE: Doctors around the world have seen some patients who tested positive for both influenza virus and the COVID-19 virus. At least a couple dozen or so cases have been reported - not a lot when you consider that over 26 million people have been diagnosed with COVID-19. Still...

MICHAEL MATTHAY: It is quite possible and likely that the two viruses could infect a patient at the same time or, for that matter, sequentially - one month, one virus, and the next month, the other virus.

GREENFIELDBOYCE: Michael Matthay is a professor of medicine at the University of California, San Francisco. He says both viruses can cause dangerous inflammation in the lungs. That can fill the air spaces with fluid, making it difficult to breathe.

MATTHAY: It's likely with both viruses at the same time the severity respiratory failure would be greater, or, of course, having two illnesses in a row that affected the lungs would make the respiratory failure more severe.

GREENFIELDBOYCE: The truth is, though, COVID-19 is so new we just don't have the research to know for sure. Generally speaking, co-infections are common when it comes to respiratory diseases. Helen Chu is an associate professor of medicine at the University of Washington. In the past, she's checked sick folks with tests for 10 to 20 different viruses.

HELEN CHU: And we often find the presence of more than one virus at a time.

GREENFIELDBOYCE: That doesn't necessarily mean there's actually more than one active infection.

CHU: You could be at the end of your illness. So you're no longer symptomatic from it, but you can still detect, you know, non-viable virus.

GREENFIELDBOYCE: Researchers have also looked to see if having more than one virus says anything about how sick you get. It can really vary depending on the viruses involved. Chu says it's unclear if rhinovirus, a common cold virus, can make a bout with flu worse.

CHU: But for a lot of the other viruses that are known causes of disease, like parainfluenza virus, human metapneumovirus and human coronavirus, those can work with flu and cause you to have more severe disease.

GREENFIELDBOYCE: Not everyone agrees on that, though. There's conflicting data out there, and some epidemiological research shows that respiratory viruses seem to compete with each other in a way that means one virus can suppress another. Tanya Miura is a virologist at the University of Idaho. She says when a new pandemic flu virus swept through in 2009...

TANYA MIURA: It was delayed in certain populations that were having, like, ongoing outbreaks of other respiratory viruses at the time.

GREENFIELDBOYCE: All the recent social distancing does seem to have reduced the number of circulating respiratory viruses. But flu is still out there, and its symptoms are very similar to those of COVID-19. Sarah Meskill is an assistant professor in pediatrics and emergency medicine at Baylor College of Medicine.

SARAH MESKILL: Just because you test positive for the flu doesn't mean you don't have coronavirus. You should still be doing your social distancing and quarantining.

GREENFIELDBOYCE: And, of course, there is one way to avoid a possible double whammy of flu and COVID-19 - get your flu shot. The vaccine will protect you, and reducing flu cases will also help hospitals that are already struggling to cope with COVID-19. Nell Greenfieldboyce, NPR News.

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