Wealth may not be the only thing people spread when they fork over funds. Researchers warn that banknotes may be reservoirs for the common flu virus. Researchers report in the journal Applied and Environmental Microbiology that human influenza viruses can survive on for as long as 17 days.

But here's the good news: just because the flu virus can survive on a banknote does not necessarily mean touching money will put a person at risk for flu infection. What's more: U.S. bills may not be as hospitable to the germs as other currency, as microbiologist Peter Palese of Mount Sinai School of Medicine suggested in National Public Radio's most recent Science Friday broadcast.

"We didn't study directly the transmission from banknotes to fingers and from fingers to upper respiratory tract," says study co-author Yves Thomas, director of the National Influenza Research Centre at Geneva University Hospital. 

Studies suggest that the virus can only live on the skin for up to five minutes, which might be due to a variety of factors including temperature and pH of the skin, says Allison Aiello, an epidemiologist at the University of Michigan in Ann Arbor. That means, she says, that "even if it's on the bill, you are in much better shape if you can inactivate it on human skin." The best way to do that?  Wash your hands frequently and do not touch your eyes, nose or mouth unless you have done so immediately before. Aiello says, "The reason I recommend frequent hand washing during influenza season is because the eyes, nose, and mouth are all membrane passages for self-inoculation with the flu virus which then makes it's way to epithelial cells, usually in the nose, throat and lungs where it replicates."

In addition, says Thomas, not all banknotes have the ability to shelter live viruses like the Swiss currency (Swiss franc) he and colleagues used in their study.

"The composition of banknotes is different from one country to he other," he says, noting that he has no clue whether the findings would translate to U.S. dollars or other international paper currency. But whether the money's dirty or not, the best way to avoid the flu, says Aiello, is to get the flu shot and scrub those paws frequently.

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