Whether a car is teeming with germs also depends on where you live. Climates that are warmer and more humid like Florida produce more bacteria, because the car's interior acts like a sauna, while Chicago's cold and damp conditions mimic refrigeration inside an automobile and encourage the growth of mold.
Gerba has also done similar studies on planes and buses, and found that cars were the moldiest of all forms of transportation, probably because their interiors get cleaned less frequently. If you're sensitive to mold, your car might trigger an allergic reaction, especially in colder climates.
While the exterior looks of your car might be of primary importance, experts advise you not overlook the inside and clean it as regularly as you would the outside.
Today's car has become more of an extension of the domestic environment -- where people eat and drink and talk on the phone. It's like a room of your house on wheels, said Hilton. Just imagine what a microbiologist might find in your dining room should you choose to foresake cleaning it for a time.
You'll want to periodically clean and wipe the surfaces and mats, especially after food or beverages spill, as well as vacuum the rugs and seats where crumbs and debris can settle. You also need to be more vigilant if your pet regularly joins you for a ride.
"I don't want people to freak out and throw bleach in their cars," said Hilton.
But Gerba takes a stronger stance. He recommends using disinfecting wipes on the dashboard, door handles and kids' car seats, especially if you're transporting lots of children or have a carpool.
It's highly unlikely that the microbes in the average car will make you sick, but under atypical circumstances, they can, pointed out Philip Tierno, a microbiology professor at New York University and author of "The Secret Life of Germs."
The real risk is driving with more passengers in the car, particularly younger ones, which increases the odds of more people sneezing and coughing, leaving a trail of germs behind that you might touch to your nose, mouth or eyes, leading to a cold or flu.
"Children are little bags of germs and if you cart them around, they have more potential pathogens," said Tierno.
Gerba put it another way, "If you're a soccer mom, you're essentially driving a germ-mobile."
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