How the Flu Spreads — and Ways to Protect Yourself
Expert tips for staying healthy when the virus is all around you
En español | Coughing, sneezing, close contact: These are among the ways the flu spreads from one person to another, causing unpleasant symptoms like cough, sore throat and muscle aches to set in anywhere from one to four days after infection — and in some cases making people contagious before they even know they are sick.
This year, experts aren't just worried about the toll of flu season, which typically peaks between December and February in the United States. They're also concerned about the possibility of a “twindemic” — the overlap between the ongoing COVID-19 pandemic and the upcoming flu season — which, they say, makes public awareness about how the flu spreads and how to stay healthy more important than ever.
How the flu spreads
"The major mode of transmission with influenza is by droplet,” says Keith Roach, M.D., an internist at Weill Cornell Medicine and NewYork-Presbyterian. When someone with the flu coughs, sneezes or even talks, he or she produces respiratory droplets containing the virus that can land in the mouths or noses of others nearby, making them sick.
According to the Centers for Disease Control and Prevention (CDC), this kind of person-to-spread spread is possible at distances of up to 6 feet — and adults who get the flu can infect other people starting one day before they develop symptoms.
Direct contact is the second way flu spreads, Roach says, like shaking hands with an infected person who just rubbed his own nose or touched his eyes (or touching a doorknob or other surface he touched) and then touching your own mouth or nose.
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But not all exposure to the flu virus is created equal. Experts say that contact with infected surfaces is generally less of a concern than person-to-person spread, and even then, variables remain.
"Someone's risk of getting infected with either flu or SARS-CoV-2 is related to some extent to the concentration of virus that you're exposed to [multiplied by] the amount of time you're exposed to it,” says Dean Winslow, M.D., an infectious disease physician at Stanford Health Care and professor of medicine at Stanford University. “Very brief exposures to relatively small amounts of virus — you're much less likely to get infected.”
Expert tips for avoiding the flu
With the goal of minimizing one's exposure to the flu virus in mind, Winslow and other experts say that many of the precautions people are already taking to slow the spread of COVID-19 — like wearing face masks, staying 6 feet away from others and practicing proper handwashing — will theoretically slow the spread of flu as well.
But experts agree that while continuing to observe social distancing and related hygiene measures is important, the most important way to avoid the flu is by getting a flu shot — ideally by the end of October.
"Vaccines are really our best line of prevention,” says Pedro Piedra, M.D., a professor of molecular virology and microbiology and of pediatrics at the Baylor College of Medicine. He notes that the flu shot not only reduces the likelihood of getting the flu in the first place but also reduces the severity of illness if someone does become ill.
Piedra also recommends that older adults talk to their physician about having a prescription for the antiviral drugs used to treat the flu easily available or filled in advance. Antiviral drugs can make flu symptoms less severe and can also reduce the risk of serious flu complications but are most effective when taken within two days of symptom onset, which makes prompt treatment — and easy access to a prescription — key.
As for staying in general good health to fend off a flu infection, the experts agree: Skip special supplements or vitamin regimens and focus on the basics, like getting adequate rest, making time for regular exercise and eating a well-balanced diet.
Once you've taken all the necessary steps to protect yourself? Help create a “wall of protection” for those around you by telling your family, friends and caregivers to get vaccinated, too, Piedra says.
“Working as a team,” he says, “is the best way to try to stay protected.”