Short Wave - Never had the flu? Scientists may know why

Episode Date: April 3, 2026

Scientists estimate somewhere between 5%-35% of people do not get sick from the flu despite being exposed to the virus that causes it. Now, researchers may have figured out why. The team looked at mouthwash samples from 19 healthcare workers who, despite frequent contact with infected patients, report never getting flu symptoms. Today on Short Wave, we talk about how what they found could help scientists develop treatments and strategies to protect people who do get the flu. If you liked this episode, check out our show on an effort to map the entire immune system.Interested in more health science? Email us your question at [e-mail] to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, shortwavers. Emily Kwong here with my co-host, Regina Barber. Hey, I'm. Hi, and Juana Summers. One of the many awesome hosts of all things considered. Aren't you so excited to take a break from the hard news? It's always fun hanging out with y'all. Oh, we are fun. Excellent.

Well, this episode is our biweekly science news roundup where we wax poetic about some of the most interesting science stories we found online in the journals in pop culture, anywhere cool science could be happening. Sounds like most off on the journals. Yeah, that's just true. Science is happening around us all the time. But this week, those stories we found are mostly focused on health. See? Like, that is around us, right? It's true.

Have either of you gotten the flu this season? This is my important question for our show. Knock on wood, not yet. Me neither. I got a vaccine, so no. Yeah, awesome. Awesome. Well, I'll be curious to see, like, what you think about this first topic because we are talking about people who have never gotten the flu.

And then we're going to talk about something that I think Wana is going to be interested in exercise. Yeah, I'm a runner. I'm excited for this. Our second story also may change up your routine because it's about why you may need less vigorous exercise than you think. Interesting. And then I think we're going to round it all out with a study on the effects of fortifying food, right? That is right. Food, flu, and fitness today on the show. Let's get healthy. You're listening to Shortwave, the science podcast from NPR. Okay, Gina and Wana. I have gavats.

gathered us all to this fine studio in the depths of NPR to chat about some new interesting health studies. Okay. Wana, which one do you want to talk about first? Okay, I want to start off with this flu story because I am not a person who really gets the flu. I don't think I've actually ever had it before. What about you guys? That is ridiculous. Crossing my fingers. I might have just janked myself. Good for you. The flu heard you. Let message us next week. So it sounds like this story is kind of about people like me who don't get the flu. And so scientists seem to have a clue now as to why. Yeah, so scientists found a lot of this one small protein in the noses and mouths of people who reported never getting flu symptoms. And that seems likely to protect them from the flu virus. And this study was published in the journal PNAS. How'd they find this out? Yeah, scientists found a special group of participants for this study, 19 healthcare workers. So 19 people who had a ton of close contact with sick patients, but never once had.

flu-like symptoms themselves. These folks also had never had a flu vaccine in their lives. And guess who the first study participant was? Okay, I'm not going to get this right. Was it the surgeon general? Nope, nope. It was one of the researchers' moms. I love that. I always tell her that she has a superpower. Mariam Ferrer Garcia is a virologist who worked on the study. She's based at the Fisabio Foundation in Spain.

And she always wondered why her mom, who's this retired nurse, managed to never get the flu. So Mariam and her team collected mouthwash samples from healthy health care workers in search of a reason. And they found high levels of this protein called dermcidin. It seems to block the flu virus before it even gets into cells. But this is not what dermcidin was known for. Okay, hold up for a second. Scientists already knew that some people had this protein.

Yes. Dermcidin is found in human sweat where it blocks bacteria and fungus from infecting our skin. But what scientists didn't know is that dermcidin is an antivirus. too. Yeah. So compared to healthy people who have definitely had the flu before to these like flu resistant health care workers, they had a much higher level of dermcidin in their saliva and nasal passageways. Okay. Let me see if I understand this. So the amount of this protein is ramped up in some people, even before a person is exposed to the flu? Yeah. Scientists don't know exactly why some people have different levels of dermcidin. But Mariam says that measuring the amount could help identify people who may be at

risk for getting very sick from the flu, and then making sure those folks get a flu vaccine for sure. Scientists also want to explore how to use dermcidin as an antiviral and as a preventative treatment. Like in a nasal spray or something? Yeah, nasal spray or even eyedrops with derm cyden that could protect someone. The research has also found that dermcidin blocked measles, one of the viruses that causes the common cold, and multiple strains of the flu, including a strain that's already resistant to current antivirals. Interesting. All right. Let's move on to topic two. which is about vigorous exercise. You guys both know that I'm a runner, but sometimes it's more of a jog than a sprint.

Is that okay? Yeah, almost only jog. But, Juana, if you're getting at least 15 to 20 minutes of this vigorous exercise a week, then yeah, you're doing great. Yeah, researchers discovered this by looking at survey data showing the exercise habits of over 96,000 people in the UK. And they found that people who put in just a few minutes of vigorous exercise a day, We're less likely to develop serious conditions such as heart and kidney disease, type 2 diabetes, and dementia. Okay, so I have questions for you guys. And the first one is this. What actually counts as vigorous exercise? Yeah. It's a really good question. Yeah. So do you have a heart rate monitor?

I do. I've got a little heart rate monitor on my wrist. Well, it depends on your age. But generally speaking, the American Heart Association defines vigorous exercise as your body reaching 70 to 85% of your max heart rate. It's different for different ages and health levels. I spoke to the lead researcher of the study, Ming Shui Shen, and he said that even small things could count as vigorous exercise, like going up the stairs quickly or carrying heavy groceries or short bursts of cycling or running, which is really a good reminder for people who can't do like a ton of cardio. And this was surprising to the scientists? It was at least to Ming Shui. We are very surprised. We expected the higher intensity activity could be beneficial.

But we were struck by how much more important intensity was than total volume. Because the American Heart Association suggests 75 minutes of vigorous exercise a week. And then along comes this study saying maybe you don't need that much. Interesting. And it's also worth noting that the American Heart Association says that you can alternatively do 150 minutes of moderate exercise. But this study suggests it's best to prioritize the short bursts of intensity during that workout. Interesting. What do people in the sports world, though, have to say about all of this? Yeah, so that's what I thought, too. And one expert I talked to wasn't that surprised. In fact,

he says that during workouts. If you look at like the collective time that people are actually engaged in that high intensity, it's not a lot. This is Dr. Eli Friedman from Cedars Sinai in Los Angeles. He trains athletes. So he wasn't surprised, but he also wanted to caution that even though vigorous exercise is important, he doesn't want people to be discouraged from doing less. intense exercise. Any exercise is good. And that this study, it shows pushing yourself a little, even for a few seconds, can go a long way. Okay, I'm going to keep that in the back of my head when I go to the gym tomorrow. Yeah, let's go sprint after this up some stairs. I literally sprinted for like 30 seconds after I did this story. Okay. And do we all feel ready to move on to the final topic?

I think it's food fortification. I do not know what that is. Please help. Yeah. It is so technical sounding, but fortified foods are pretty common. You've probably had iodized salt in a salt shaker. That's fortified with iodine. There's bread, fortified with folic acid and breakfast cereal, fortified with iron. You're thinking of something like Wheaties? Yes, I am. Yeah, I just ate fortified cereal this morning. It was like cinnamon checks. Yum. And basically, fortified foods contain carefully calculated boosts of essential vitamins and minerals because billions of people around the world are not getting enough micronutrients. And over time, a micronutrient deficiency has serious health consequences. From susceptibility to disease, to impaired growth and development for young

children especially. Mduduzzi Mboya is the co-author of a new study in the Lancet Global Health, which measured the impact of large-scale food fortification programs in 185 countries. And his team found that based on the best available data, these programs prevent seven billion nutrient gaps, worldwide. So this is basically evidence that these programs do have a massive impact. And they estimate that even more nutrient gaps could be prevented if food fortification programs had higher compliance. This involves manufacturers consistently fortify in staple foods at the levels required by national standards. As an example, a nutrient gap in folic acid has been linked to neural tube defects in infants. And that's why California now requires

manufacturers to add folic acid to corn, moss of flour. which is used to make tortillas. Yeah, Alabama will follow suit with a similar law in June. So my big takeaway here is that I definitely need to eat more vegetables and tortillas, huh? But you also need to, like, sprint just a baby, baby amount sprinting. Just a little bit. I'll sprint out of the studio soon. Okay.

Ready, set, go. Okay. No, before you run off, Gina, Juana, thank you for hanging out and talking about all things personal health with me today. Let's do it again soon. Yeah. For more science stories just like these, follow Shortwave on whatever app you're listening to. It helps you never miss a new episode. And if you love Wana as much as we do,

check out our work on Consider This, NPR's afternoon podcast about what the news means for you. It's really good. Go ahead. This episode was produced by Jordan Marie Smith and Burley McCoy. It was edited by a showrunner Rebecca Ramirez and Patrick Jaron, Jaron, Jaron, Jaron, Jaron, Jaren, Watan. Tyler Jones checked the facts, and Hannah Glovna and Robert Rodriguez were the audio engineers. I'm Emily Kwong. And I'm Regina Barber.

Thank you for listening to Shirtwave, the science podcast from NPR. Let's get physical. Physical. Do you know Gina used to be in a band? I did not. Yeah, she was in a punk band. I was in a grunge band. Okay, I don't even know the difference between these things.

Because I was born, I never saw the 80s. I mean, grunge was in the 90s, but it's cool.