Hot and humid summers mean mosquitoes. And the annoying insects spread more than just itchy welts – they can transmit painful and sometimes deadly diseases.
At least 497 people in the continental U.S. as well as Puerto Rico and the U.S. Virgin Islands have contracted the chikungunya virus so far this year, according to the Centers for Disease Control and Prevention -- 140 of them in the past week alone.
For most of us, mosquito bites are just a nuisance. And some people have it worse than others.
What makes a person a mosquito magnet? Read on to learn how some seemingly harmless habits like a daily run or a backyard beer could make you a more appetizing target.
It turns out mosquitoes don’t bite randomly. Instead, they hone in on a victim by following a steady output of carbon dioxide.
Richard Pollack, an instructor at the Harvard School of Public Health and adviser to the Massachusetts Department of Agricultural Resources, said mosquitoes are adept at figuring out where their target is by following these exhaled trails.
“If you were to exercise vigorously, you would produce more carbon dioxide for a brief period,” Pollack told ABC News. “You might [then] perhaps be a little more attractive to mosquitoes.”
Unfortunately, there’s no good way to cut down on carbon dioxide aside from holding your breath, Pollack said. So if you’re getting bitten, you might want to head inside.
While carbon dioxide is how mosquitoes lock onto you as a target, heat may be how they figure out where to bite you.
Dr. Jonathan Day, a professor of medical entomology at the University of Florida, said that before mosquitoes can take a bite they have to find an area of the body where the blood is close to the surface. Common areas include the forehead, wrists, elbows and neck.
However, people who are over heated or who just finished working out will have blood closer to the surface of the skin throughout their body.
“They use the heat to very quickly to determine where blood is closest to the surface,” said Day.
Although a few small studies speculated that mosquitoes were after specific blood types, CDC say that's false. By the time the mosquito bites you, they've picked you as the target, they said.
If you’re heading to a picnic and looking to avoid becoming a mosquito’s meal, Day recommends avoiding any dark denim or all-black outfits.
“If you dress in dark colors you stand out against the horizon and mosquitoes [can see you,]” said Day.
Some mosquitoes are visual hunters that search you out by looking for signs of life against the horizon, Day said. Movement can also draw the insects in, so hikers on the move should wear plenty of bug-repellent, he added.
The results of a very small study suggest that drinking a bottle of beer could make you a target for mosquitoes, though CDC experts say there's no good evidence that consuming certain foods or drinks ups your risk for bites.
The study of 13 volunteers found that mosquitoes were more likely to land on subjects who had recently guzzled a beer. But blood alcohol tests failed to link alcohol ingestion and mosquito landings, so the jury's still out on why volunteers with beers got more bites in the study.
In addition to heat and carbon dioxide, mosquitoes are also attracted to naturally-occurring chemicals that are released as people breathe.
Day said carbon dioxide and heat will draw the mosquitoes to a crowd, but these chemicals, called secondary attractants, can lure the insects to one unlucky person at a barbecue.
The chemicals vary, but one is related to estrogen, which Day said could be the reason women are often bitten by mosquitoes.
Aside from exhaled chemicals, the mosquitoes can get drawn in by lactic acid, CDC experts said. And people tend to produce more lactic acid when they're exercising.