You know those enviable people who seem like they never, ever get the flu? Even though they're exposed to the virus, they just don't get sick from it.
Now, new research reveals that it may not because the virus doesn't infect these people -- rather, their genes keep them from developing symptoms of the flu, and they can still be contagious and pass the virus on to others.
"Many people might conclude that if you are exposed to a virus and you don’t get sick, it’s because the virus didn’t stick or it was so weak, it just passed right through your system and your system didn’t notice. That’s not a correct notion," study researcher Alfred Hero, a professor at the University of Michigan, told MSNBC.
Hero and a team of Duke University researchers inoculated 17 people with the H3N2/Wisconsin strain of flu virus, and drew blood samples from these volunteers every six to eight hours. The researchers then used those blood samples to look at their genes to see if any of those associated with immunity were active.
After about five-and-a-half days, nine of the people came down with symptoms of the flu, but blood tests revealed that all 17 people were actually infected with the flu and that their bodies were making flu antibodies, according to the PLoS Genetics study.
The symptom-free volunteers showed activity in genes performing antioxidant and anti-inflammatory functions, but their bodies' acute inflammatory responses were not active, said Alfred Hero, a co-author of the paper. Meanwhile, blood samples from the sick volunteers showed different, or even opposite, gene activity, Hero said.
Even though the number of people involved in the study was small, the quantity of blood samples gathered -- 267 -- and genes examined -- 22,000 -- was the largest done on the human immune response, the scientists explained.
Researchers also said that the discovery could help them to detect the flu early, since flu-sufferers developed a "genetic signature," signaling inflammation 36 hours before the worst of the flu symptoms set on, the Daily Mail reported. This would give people a "running start" to take preventive measures to stave off the worst flu symptoms, they said.
Symptoms of the flu include having a fever over 102 degrees Fahrenheit, feeling nauseous and fatigued, having muscle aches, chills, stuffy nose, headache and cough, and having a loss of appetite, according to the American Academy of Family Physicians.
To stop mild symptoms from becoming worse, the AAFP recommends getting rest, avoiding secondhand smoke, drinking lots of fluids to loosen mucus and gargling with warm salt water to soothe sore throats. For severe flu, a doctor can also prescribe antiviral medicine that can be inhaled, swallowed as a pill or taken as a syrup.
Aside from genes, there are other things you can do that can decrease your risk of getting sick. Some of these include remaining active and exercising, which increases circulation and thereby white blood cells that eat up germs, as well as getting enough sleep to restore the immune system, according to WebMD.
In addition, simply getting older could make you immune to certain strains of flu, Wired reported. Because an older person has been exposed to -- and possibly even vaccinated against -- many past strains of flu, their bodies may already have antibodies to more current strains that are similar to those past strains, according to Wired.