Can You Get the Flu From Touching a Sneezy Handle?

You’re far more likely to get the flu from breathing in the virus when you’re around someone who has it than you are from touching infected items around your house, say researchers from Great Britain.

Most household materials can’t sustain enough influenza—the virus which causes the common disease we call “the flu”—to infect another person by physical contact after only a few hours. These results confirmed what most scientists suspected: the influenza virus is quite fragile.

To test the survival of the virus on household items, researchers deposited small amounts of influenza on items like light switches, toys, kitchen counters, keyboards, and window glass in a laboratory setting. Then they measured the amount of viable virus (meaning a large enough quantity to lead to an infection) at set times.

On all surfaces tested, there was no longer any viable virus after nine hours. In fact, most surfaces could be considered “contamination free” in four hours or less. Hard, non-porous materials such as stainless steel allowed for longer survival times while softer, porous materials like wood allowed for the shortest.

According to Jane Greatorex, lead scientist on the research team and senior research scientist for the Health Protection Agency at the University of Cambridge, the biggest surprise in these results was the relatively long survival times observed on stainless steel, a common material in hospitals, compared to other materials.

On “stainless steel, the virus survives a little bit longer, which perhaps isn’t so good in a hospital setting,” she says. “Stainless steel is often used on things like bedrails and sinks and door handles—that might not be ideal.”

Epidemiologist Rene Najera of the Communicable Disease Surveillance Division at the Maryland Department of Health and Mental Hygiene says the awareness of virus survival time on stainless steel could lead to improved interventions in hospital cleanliness guidelines, a key component to pandemic response planning.

“Where you see these places that are spotless but they’re all covered in stainless steel—they’re easier to clean but unfortunately, as we saw in the study, the flu virus liked it a lot,” says Najera. “So you would recommend, if you’ve got stainless steel, clean it often and clean it well during flu season.”

Jonathan Van-Tam, professor of health protection at the University of Nottingham and co-author of the study, thinks even the stainless steel results should come as a reassurance to people. “If you think about an office, where people go home at six p.m. in the evening, by the time people come back in at eight a.m. in the morning, people shouldn’t be fretting too much about viruses left over from yesterday,” says Van-Tam. Normal surfaces probably don’t have to be intensely sanitized “because it’s unlikely there will be any virus left.”

Another important aspect, notes Van-Tam, is that there are many critical factors that must line up for contact transmission to occur. After enough of the virus has been applied to a surface by coughing, sneezing, or snotty hands, the virus needs to survive long enough to pass on to somebody else. Then it has to survive on the person’s hands and be rubbed against a mucus membrane on the patient’s face, like the eyes, nose, or mouth. If enough virus is still alive at that point, it still has to have a high enough concentration to be infectious.

These results clear up some uncertainty about the transmission methods of influenza and have already brought about changes in public health policy in Great Britain. The team fed their results immediately to Great Britain’s Department of Health, says Greatorex. This resulted in a change to the national advertising program used for spreading the word about influenza control.

“We were able to confirm that we were getting out the correct messages—that you’re most likely to catch this virus by being sneezed on or being in close proximity to sick people,” says Greatorex. “The virus doesn’t really survive that well on household surfaces.”

This study and others like it are aimed at understanding the influenza virus as part of a larger effort to prevent the next big flu pandemic—or worldwide flu outbreak—like the 2009 Swine Flu pandemic which killed more than 18,000 people worldwide.

Paul Digard, co-author of the study and senior lecturer in the department of pathology at the University of Cambridge, says one of the two strains of influenza the research team used was isolated from that same pandemic, “which is about as close as you can get to the real thing,” says Digard.

“People have been planning like mad for the next flu pandemic since 2004 or 2005,” says Van-Tam.

Urgency to improve the country’s pandemic response heightened with the outbreak of bird flu in India in 2006 and resulted in a 2007 report from Great Britain’s Department of Health that targeted several knowledge gaps in influenza research. “One of the things they identified is they didn’t really know how long the virus survived on surfaces in general,” says Greatorex.

There are three ways to get the flu, says Van-Tam. Contact transmission (either directly touching an infected person and passing secretions or touching an infected surface where that person has deposited flu virus) is one of them. The other methods include aerosols (small solid or liquid particles suspended in air that travel long distances) and large droplets (generated by coughing or sneezing) that travel short distances. “And out of that comes one question: how long do human flu viruses actually survive?” says Van-Tam.

When it comes to pandemic planning, everybody seems to be interested in that one. “You get teachers or education department policy makers asking: how long will the flu virus last on a classroom table?” says Van-Tam. “I’ve even had customs and excise officials saying, at the airports: if we’re receiving freight from another country in a pandemic, is there a risk at touching the outside of freight containers? How long does the virus survive?”

In dealing with flu pandemics, planners can never be too vigilant. In 1918, an influenza pandemic (called the “Spanish” flu) killed between 50 and 100 million people worldwide (about three percent of the world’s population at the time) in one of the deadliest natural disasters in human history.

Researchers continue to strive for a better understanding of the continuously-evolving influenza virus. According to Elena Naumova, director of the Tufts University Initiative for Forecasting and Modeling of Infectious Diseases, there may be other factors that affect the likelihood of being infected by the virus. “In my opinion, all three modes of transmission occur naturally, however their relative contributions to an overall transmission pattern depend on many environmental and behavioral factors,” she says, adding that different strains of flu virus affect different age ranges and at different times of the year. Surfaces could also be re-contaminated by an infected person—all the more reason to maintain high cleanliness standards throughout flu season.