From Ebola in West Africa to chikungunya in the Caribbean, the world has had plenty of strange and scary outbreaks this year.
Some pathogens have even landed in the U.S. Just a few months ago, two men boarded planes in Saudi Arabia and brought a new, deadly virus from the Middle East to Florida and Indiana.
Nobody along the way caught Middle East respiratory syndrome. But all of these plane-hopping pathogens got us wondering: How easily do bacteria and viruses spread on commercial jets? And is there anything we can do to cut our risk?
Microbiologist James Barbaree and his team at Auburn University have been trying a few simple experiments to figure out the first question.
The airlines gave the scientists parts on commercial jets where spread might take place a steel toilet button, the rubber armrest, the plastic tray table and, of course, "the seat pocket in front of you."
Barbaree and his team sterilized the surfaces and then painted on two dangerous microbes: the antibiotic-resistant superbug MRSA and E. coli O157, which will give you an unforgettable case of diarrhea.
Several days later, the microbes were still happily thriving on the plane parts. E. coli survived about four days. MRSA lasted at least a week, the team reported at a scientific meeting in May.
Such hardiness is common for MRSA and E. coli, Barbaree says. "I'm not surprised at all the bacteria survived so long on the surfaces," he says. "MRSA has been tested on other surfaces. And in one case, it lasted over a year."
In general, the bacteria tended to stick on the plane surfaces instead of hopping onto a pig skin an experimental proxy for a traveler's hand. But some of the bugs did make the jump from the plane onto the fake hand.
If you're going to pick up a pathogen on an intercontinental flight, it will probably be one hanging out on your seat or another surface, says Dr. Mark Gendreau, who specializes in aviation medicine at Lahey Medical Center in Peabody, Mass.
"When you look at most infectious diseases, the overwhelming majority are transmitted when you touch a contaminated surface," he says. "You grab the door knob of the airplane bathroom, and then touch your eyes, nose or mouth."
"But we're not all doomed to get sick after a plane flight," Gendreau says. "You can change behaviors when you're traveling and substantially reduce the risk of catching anything."
First off, keep your hands microbe-free. "I recommend bringing aboard a sanitizing gel with 60 percent alcohol," he says. "Before you eat or drink, sanitize your hand."
And don't forget to use the sanitizer after you wash your hands in the bathroom's sink, Gendreau recommends. The water in airplanes has a dirty track record.
In 2004, the Environmental Protection Agency found high levels of fecal bacteria in the drinking water of 15 of the 327 planes it tested. Then in 2009, the agency set forth new guidelines for airlines for testing their water. Now the EPA says that water on the airplane is safe to drink if you don't have a suppressed immune system.
But Gendreau still wouldn't risk it. He wouldn't even brush his teeth with the water in an airplane bathroom. "I use bottled water," he says.
Of course, not all pathogens live in water or on surfaces. Many, such as the measles and tuberculosis, hang out in the air. Commercial jetliners recycle about 50 percent of the cabin air. So if a sick passenger is sneezing in first class, will his viral-packed air eventually reach you in the back of the plane?
Not likely, Gendreau says. Airplanes have high-tech air filters that remove more than 99 percent of dust and microbes from the air, he says. "And the ventilation is compartmentalized. So the air circulates only in part of the cabin."
But if you're unlucky and are sitting close to the sick passenger, then a flu-packed sneeze may find your lungs before it finds the filter.
Several studies have looked at how airborne diseases, such as TB and severe acute respiratory syndrome, move about on planes. For TB, the conclusions have been consistent: When you sit within two rows of someone infected with TB and the flight is longer than eight hours, there's a chance you could catch disease.
But the size of this "transmission zone" depends on the specific pathogen.
Take SARS, for instance. Back in 2003, a 72-year-old man boarded a plane from Hong Kong to Beijing. He had a fever on the flight. And when he got to mainland China, he was hospitalized. About a week later, the man died of SARS.
During the three-hour flight, he had infected 22 other passengers with the virus. About half of those people were sitting within three rows of the ill man. But even passengers seven rows in front of him caught the deadly virus.
Don't fear, Gendreau says. There's even a way to protect yourself from these airborne pathogens: Take advantage of that vent above your head.
"Set your ventilation at low or medium," he says. "Then position it so you can draw an imaginary line of current right in front of your head. I put my hands on my lap so I can feel the current so I know it's properly positioned."
Then if something infectious is floating in your personal space, he says, that air from the vent will create enough current to knock it away. And you'll be more likely to go home healthy.