To reduce the risk> of catching swine flu, the Centers for Disease Control and Prevention recommends frequent hand washing and using tissues when you sneeze. But there's another way to protect yourself even if it's not so good for the economy: Stop spending money.
It doesn't get talked about much, but the fact is paper currency the dollars, fives, tens and twenties most people routinely touch every day can spread a virus from one person to another. So if you have contact with money that an infected individual has also handled, there's a possibility of catching the flu.
How likely is that? Despite the pervasiveness of cash in society, its role in transmitting illness has been the subject of surprisingly little study. But some recent research suggests that flu bugs can show some staying power when they land on one of the countless banknotes that change hands every day.
Generally speaking, scientists interviewed by SmartMoney estimate the lifetime of a plain flu virus deposited on money at an hour or so. But mix in some human nasal mucus, and the potential for the virus to hang on long enough to find a victim increases, according to one of the few scientific studies done on flu transmission through cash.
In a study conducted at Switzerland's Central Laboratory of Virology at the University Hospitals of Geneva, researchers tested to see what would happen when flu virus was placed on Swiss franc notes. In some of these tests, researchers placed flu virus mixed in with nasal secretions from children on banknotes and saw some unexpected results.
When protected by human mucus, the flu cells were much hardier in some cases, lasting up to 17 days on the franc notes. The virus that persisted for 17 days was a form of influenza A called H3N2. In an email interview, Dr. Yves Thomas said samples of an influenza A strain called H1N1 also endured for quite a bit in some cases, up to 10 days. That bug was similar but not identical to the virus at the center of the current swine flu outbreak, which is considered a new strain of H1N1.
Read the full study, "Survival of Influenza Virus on Banknotes," in the May 2008 issue of the journal Applied and Environmental Microbiology here
To be sure, many kinds of frequently touched surfaces could temporarily harbor the flu virus. Broadly speaking, scientists consider the risk of transmission in this way to be low, particularly if hand-washing and other hygiene measures are practiced, says Dr. Philip Tierno, director of clinical microbiology and immunology at New York University's Langone Medical Center and author of "The Secret Life of Germs."
Three things must happen for a flu virus to be transmitted from one person to another via money. First, a person who is infected with the swine flu must sneeze or cough onto the bill or blow their nose and leave remnants of their mucus on the currency. Next, an uninfected person would need to touch the money while the virus is still present.
Finally, that person would need to put their contaminated hand in their mouth or pick their nose, says Dr. Murray Grossan, an otolaryngologist at Cedars-Sinai Medical Center in Los Angeles.
As public concern and media hype about the swine flu outbreak grows, it's remarkable how little the subject of money comes up and how few people want to discuss it. The CDC wouldn't discuss the role of money in flu transmission. At the New York State Health Department, spokeswoman Claire Pospisil declined to comment. And when we asked the U.S. Bureau of Engraving and Printing that's the government operation that actually manufactures money a spokeswoman told us that what happens to U.S. dollars once they're in circulation is beyond the bureau's control.
Meanwhile, concern about the potential spread of swine flu continues to grow in the U.S. and abroad. On Wednesday, the World Health Organization raised its pandemic alert level to phase 5, one level shy of WHO's highest readiness. As of Thursday afternoon, there has been one confirmed swine flu death in the U.S. -- a 23-month-old Mexican child brought to Texas for treatment. Also as of Thursday afternoon, the tally of confirmed U.S. cases of swine flu stands at 109, measured from when it was first identified as a new strain on April 24. To put those numbers in perspective, an estimated 36,000 Americans die annually from complications related to regular seasonal flu strain, according to the CDC.
Still, if all this has you looking more suspiciously at the folding money you're carrying around, you could consider relying more on coins. Scientists say those are much more likely to be virus-free since metals like nickel and copper inhibit viruses.
And even the humble dollar bill may have some defenses. The ink on freshly-printed U.S. dollars has a fungicidal agent in it that can inhibit the growth of bacteria and fungi and the influenza virus can be killed more easily because of it, says Tierno. As the dollar gets used and abused especially with perspiration or water the strength of the ink weakens, he says.
As for the paper, Peter Hopkins, a spokesman for Crane & Co., the exclusive provider of paper for U.S. currency, says he doesn't know whether the paper has any antiviral properties, but says it is made out of 75% cotton and 25% linen (he wouldn't disclose the other elements). Tierno says that those natural fibers can be degraded by fungus. And, therefore, to prevent that from happening, the pulp -- like the ink -- also includes a fungicidal agent.
One big unknown at the moment is whether the swine flu will continue to mutate and grow stronger, says Dr. Rani Bright, assistant professor of pathology, microbiology and forensic medicine at Philadelphia College of Osteopathic Medicine. If it does, the virus could conceivably survive on dollar bills for an even longer period of time.
When severe acute respiratory syndrome, or SARS, first broke out in China, some researchers expected the virus to survive on currency and other surfaces for just a few hours. Instead, it lasted a few days because it was much stronger than originally anticipated, says Dr. Jean Patterson, chair of the virology and immunology department at the Southwest Foundation for Biomedical Research in San Antonio, Texas.
Even after the spread of swine flu subsides, consumers may want to continue being cautious when handling their cash. Some infectious bacteria, such as Staphylococcus aureus and Klebsiella pneumoniae, can stick to currency for a longer period than viruses, according to a 2002 study that was published by the Southern Medical Journal, titled Bacterial Contamination of Paper Currency. Dr. Peter Ender, an infectious diseases physician at St. Luke s Hospital & Health Network in Bethlehem, Pa., who co-authored the study said that while the average health risks are low, bacteria on U.S. dollars could cause mild or serious illness.
Are there ways to make cash cleaner? One approach: ATMs that sterilize your money. Some years back, just such a machine was marketed in Japan, where cleanliness can be something of a cultural obsession. These "clean ATMs" were manufactured by a Hitachi subsidiary, Hitachi-Omron Terminal Solutions. However, according to Hitachi spokeswoman Lauren Garvey, those machines were not available outside of Japan and are no longer manufactured.
There may be a much simpler solution if you don't mind making the credit-card companies richer. Paying by credit card instead of cash could lower your risk of catching a bug, says Patterson. That isn't because of any special properties of plastic, but because your credit card typically passes through fewer hands than cash reducing the chance of contact with an infected individual. But don't throw away your bottle of sanitizing gel. Viruses can still live on your plastic for up to an hour or so, she says.