Fever, muscle aches, nausea - these are what we usually associate with having the flu.
But just because you don't exhibit these symptoms, it doesn't mean you don't have the flu, researchers say. And you could be just as contagious. In fact, their study found that roughly three quarters of people with seasonal or pandemic flu show either no symptoms or mild ones that aren't usually linked to flu.
"[The] flu is more common than we thought, but often less severe than what we had thought," says Andrew Hayward, an epidemiologist at University College London and the study's lead author.
People often mistake the flu for the common cold, Hayward tells Shots. "A lot of the time you may just have a runny nose, a bit of a cough, perhaps a sore throat," he says. But the classic flu symptoms of a sudden fever and muscle aches - "the study shows that that very often doesn't happen. And it's often a much more mild illness."
The study tracked nearly 5,500 people across England over six flu seasons between 2006 and 2011, including the 2009 H1N1, or swine flu, pandemic. Researchers drew blood samples before and after each season from each participant to check for signs of the infection.
They then contacted each household every week to check for cough, cold, sore throat or flu-like illnesses. Those who reported these symptoms then submitted nasal swabs to test for influenza and other respiratory illnesses.
Roughly 1 in 5 unvaccinated people were infected with the flu virus each winter, the study found, but only a quarter of those people showed any symptoms of the infection. And only 17 percent of those infected were sick enough to see a doctor.
Contrary to previous reports of the H1N1 influenza causing more severe symptoms than the seasonal flu, researchers found that people who had the 2009 pandemic strain, a newer one that many people have less resistance to, actually showed milder symptoms. Hayward says this calls for a better understanding of the severity of not only seasonal flu, but of new strains when it comes to developing preventive measures.
The results, published Monday in The Lancet Respiratory Medicine, suggest that commonly used statistics based on the number of hospital visits and deaths significantly underestimates the extent of flu infections and illnesses.
"If you want to understand how severe it is, you really need to understand not only the number of people who end up in hospitals or die, but also the number of people in the community who are infected in the first place," Hayward says. "So we need better methods of picking those people up."
He adds that though there needs to be more research done, it may be that some the people who have milder symptoms are still potentially infectious, which calls for doctors to rethink some of the initiatives on how to stop the flu from spreading.
According to Hayward, few people visit the doctor when they have the flu, and even when they do, doctors rarely diagnose them as having influenza.
It's not enough, he says, to just tell people to stay home to avoid spreading the illness, especially if they aren't struck with the debilitating symptoms of a severe flu. And while flu vaccines are still important, they aren't 100 percent effective among healthy young adults and even less so among the elderly population.
But this study should not be taken to mean that the flu is as trivial as the common cold. "The flu is very common, and often mild, but that doesn't mean that we shouldn't take it seriously because from time to time it can lead to very severe complications," he says.
And while doctors work on rethinking the spread of flu, Hayward says people can protect themselves by getting vaccinated and by regularly washing their hands.
South by Southwest 2014 is a wrap, and it's hard to quite comprehend how much was packed into its five days. Which is why we've put together a handy guide to a small sampling of the massive quantity of music we consumed in Austin last week.
Start with a few of the 97 photos from the annual music festival. Sample video from Kelis' set at our SXSW showcase. Take a listen to the interviews and podcasts recorded live on Austin's streets in the wee hours of the morning. If you're feeling overwhelmed, try slowing things down with our slo-motion videos. It might be enough to keep you occupied until next year.
Interviews and Keynotes
Neil Young Explains His Pono Music Player: For years, Young has been working on a digital music player that would prove how terribly we've compromised our listening experience. On Tuesday at SXSW, he explained how Pono is supposed to work. Hear the whole thing here.
Lady Gaga At SXSW: 'Don't Sell Out. Sell In.': We're not sure precisely what that quote means either, but Gaga made plenty of strong, surprising points during her keynote interview on Friday about the realities of being a popular artist. Watch the whole thing here.
Ana Tijoux: 'We Are Crazy As A Species': The Chilean rapper played songs from her new album, Vengo, and talked with Alt.Latino hosts Jasmine Garsd and Felix Contreras about her unique style. Hear the whole thing here.
Kevin Gates: 'I Put All My Flaws On Front Street': "The more I grow in popularity, the lonelier it gets," the Baton Rouge rapper told Microphone Check hosts Ali Shaheed Muhammad and Frannie Kelley during an interview in an East Austin back yard. Watch the whole thing here.
All Songs Considered Late Night Dispatches
Each night, after consuming as much music as they possibly could, All Songs hosts Bob Boilen and Robin Hilton, along with NPR Music's Stephen Thompson and a rotating cast of guests, met on the streets of Austin to talk about the best of what they'd seen.
Tuesday: Agnes Obel, Royal Teeth, Jambinai and what people mean when they say "Keep Austin Weird."
Wednesday: NPR Music's SXSW Showcase at Stubb's featuring Damon Albarn, St. Vincent, Kelis, Eagulls and Perfect Pussy, which was interrupted by news of the accident that killed two people, just one block away.
Thursday: The shadow cast by the previous day's accident begins to lift. Catharsis from Typhoon, The Autumn Defense and Big Freedia. Plus a unifying set by the breakout stars of SXSW 2014, Baltimore's Future Islands.
Friday: Moon Hooch's two saxophones win everyone over, but Robin has given his heart to Perfect Pussy.
Saturday: Bob discovers the secret of the universe on the dirty floor of an Austin club, and as the festival ends, we finally catch up with band's we've been trailing all week.
South by Slo-mo
South By Southwest goes by fast. So Mito Habe-Evans and our video team helpfully slowed it down. It's pretty self-explanatory. Want more? Of course you do.
Whether it's James Franco writing novels or Pablo Picasso scrapbooking, all great artists move outside their medium. Subway has recently been experimenting with pizzas. The latest is the Flatizza, which is a combination of "flatbread" and "pizza," and is also embarrassing to say when you have to order one.
Mike: Subway pizza is a tough sell. "Five-dollar foot-wide" feels wrong.
Miles: I just don't understand why Subway demands we wash down the Flatizza with a FlatSoda.
Robert: After the long winter we've had, it's handy to have a lunch that also works as an ice scraper.
Miles: Remember in the 15th century, when everyone thought pizza was flat?
Ian: The flat shape makes it an ideal food to go in Pizza ATMs. If these don't exist yet, nobody tell me.
You order the Flatizza like a Subway sandwich — the sandwich artist asks you what you want on it, and you choose from the ingredients on the other side of the sneeze guard. Then they stick it in a fast-cook toaster oven, which is either powered by nuclear fission or magic.
Ian: You can get it plain, veggie, or with everything Jared denied himself for the last 10 years.
Robert: Weirdly, I was watching a movie where Jared showed up at the door with one of these. After that, it got kind of weird.
Mike: Of all the foods at Subway, the Flatizza is the one Snoop Dogg has the easiest time ordering.
Miles: Instead of fighting with each other, New York-style and Chicago-style should both team up on Flatizza.
Mike: The slogan is "Crispy, cheesy and totally edgy"—it's like a charred Sarah Silverman.
Miles: Subway took the yoga mats out of their bread, threw some cheese on them, and called it a pizza.
Ian: Finally, the perfect bathroom tile in my life-size gingerbread house.
[The verdict: a fine fast-food pizza. There may come a day when we think of Subway as that pizza place that used to serve sandwiches.]
Sandwich Monday is a satirical feature from the humorists at Wait Wait ... Don't Tell Me!
A nonprofit organization called Pack for a Purpose is encouraging international travelers to use some of their luggage space to carry medical and school supplies to their vacation destination.
The organization has teamed up with local lodging, tour agencies and community organizations in countries across the globe to find out what items are needed, from pencils and soccer balls in schools to clothes and toiletries in orphanages.
Rebecca Rothney, founder of Pack for a Purpose, joins Here & Now’s Robin Young to talk about how setting aside some extra space in your luggage can help those in need.
It wasn’t exactly “the big one,” but people in Southern California did get a rude awakening today when a 4.4 magnitude earthquake struck. The quake could be felt from the San Fernando Valley down to Long Beach, but there are no reports of damage or injury.
Here & Now‘s Jeremy Hobson is reporting from Los Angeles this week and checks in with co-host Robin Young about what the quake felt like. He also shares what he has in store for us tomorrow and Wednesday when he co-hosts the show from NPR West.