Editor’s note: As the pandemic continues, some health advice is changing. This article has been updated to reflect the latest.

As the numbers of coronavirus cases and deaths in the United States rise, federal authorities are pleading with the public to stop buying surgical masks.

“Seriously people — STOP BUYING MASKS!” U.S. Surgeon General Jerome Adams tweeted early in the epidemic. “They are NOT effective in preventing general public from catching #Coronavirus, but if healthcare providers can’t get them to care for sick patients, it puts them and our communities at risk!”

Hours later, during a news conference following a coronavirus death in Washington state, Vice President Mike Pence, who is leading the administration’s response efforts, said, “Let me be very clear — and I’m sure the physicians who are up here will reflect this as well: The average American does not need to go out and buy a mask.”

Face masks are recommended for people who are sick and for health-care workers, and the government has contracted with 3M to produce 35 million more for the medical workforce, Pence said.

That has some people skeptical: If face masks are important for health-care workers, why shouldn’t I wear one, too? Is the government trying to preserve the stock of masks for people it believes are in greater need?

A month after those initial warnings, the government is urging people to wear a cloth covering over mouth and nose — two layers of T-shirt material will do — when they go out.

Not because the mask will protect you, experts say; but because it could protect others from you. Latest research has found that the virus can spread even before symptoms show.

But medical-grade masks aren’t needed for this purpose. And the very best protection remains staying at home whenever you can, practicing social distancing when you have to go out, and washing your hands frequently.

Health experts still worry that face masks might make people feel like they can skip all the other precautions.

Stephen Gluckman, a professor of infectious diseases at the University of Pennsylvania, said that when people who aren’t in health care buy expensive masks, they’re not helping themselves.

“They’re wasting money and giving people a false sense that they’re doing something," he said.

Standard surgical face masks — rectangular and secured with thin elastic — do not provide a tight seal around the nose and mouth. Their effectiveness depends on the illness and the size of its particles, Gluckman said.

Meningitis, for example, has large particles that a surgical face mask could effectively block. But based on what scientists know about the new coronavirus, its particles are small and could easily get around a surgical face mask, he said.

Meanwhile, surgical masks are recommended for people who are sick because the masks can limit how far germs travel when people cough or sneeze.

Health-care workers should wear masks because they are treating people who are ill and because the masks they wear are specially fitted to ensure a tight seal around the nose and mouth.

Health care workers use N95 respirators, which are made from thicker material and must be individually fitted to be sure there are no gaps, Gluckman said. Health care workers are required by federal law to have an annual “fit test” to ensure their mask has a tight seal and to demonstrate they know the proper way to wear, remove and dispose of a mask.

These hospital-grade respirators are available for purchase, but wearing one incorrectly or without a proper fit could increase your chances of getting sick, as constantly touching or adjusting the mask can expose you to any germs the mask captured.

Such masks are needed in a hospital setting because the use of breathing tubes and ventilators can cause tiny, viral particles to become “aerosolized," meaning they are very fine and easily inhaled, said Aaron E. Glatt, a physician with Mount Sinai South Nassau in New York.

“You’re standing right over a patient coughing into your face," said Glatt, a spokesperson for the Infectious Diseases Society of America. ”You’re going from one patient to another."

The mad dash to buy face masks makes sense — it’s natural to want to do something to protect yourself when faced with a novel virus. But there are more effective ways to protect against infection outside the hospital.

Wash your hands

Medical professionals say the best thing you can do to protect yourself from coronavirus — and any other respiratory illness — is to wash your hands.

“Part of the reason people are using face masks is because they don’t want anything to come into their face. But if we get people to wash their hands, it helps protect the eyes, nose and mouth," said Kelly Zabriskie, director of infection protection at Thomas Jefferson University Hospital. “You’re cutting out the route of transition into the body.”

Scientists are still learning about how coronavirus spreads, and it’s unclear how close you’d need to be to an infected individual to inhale airborne germs. But lots of germs are spread by touching infected surfaces and objects, then touching your mouth, nose and eyes — all of which can let viruses and bacteria into the body, Zabriskie said.

Hand-washing is one of the best protections against germs, but a 2018 study by the U.S. Department of Agriculture found that people aren’t doing it right 97% of the time.

Here’s the right way to wash your hands:

  • Wet your hands and slather on some soap. Turn off the tap to reduce water waste and protect the environment while protecting yourself from illness.

  • Lather up, making sure to get the fronts and backs of hands, between fingers and under fingernails.

  • Keep it up for 20 seconds — that’s about the time it takes to hum the “happy birthday” song twice.

  • Rinse, then dry with a clean towel.

Zabriskie recommends using lukewarm water, rather than scalding hot water, to reduce dry, cracked skin, which can let in germs.

When in a public restroom, use a paper towel to shut off the faucet and open the door, she said.

Change your hand towels

While your hands should be clean by the time you dry them on a towel, germs like damp environments, making hand towels an excellent breeding ground. The Cleveland Clinic recommends washing bath towels once a week and swapping out washcloths multiple times a week. If possible, spread out towels across a bar to help them dry between uses.

Hand washing on the go? Studies have found paper towels are more hygienic than air dryers.

Keep sanitizer handy

Washing with soap and water is more effective than hand sanitizers — even those that claim to kill 99.9% of bacteria. But hand sanitizer gels are still a good backup plan when you’re not near a sink. Be sure to buy one that is alcohol-based, as that is the ingredient that breaks down germs.

Other steps you can take

  • Avoid touching your face, eyes, nose, and mouth.

  • Avoid contact with individuals who may be ill.

  • Cover your cough or sneeze with a tissue, then throw it out right away.

  • Stay home if you’re unwell.

  • Disinfect frequently used items and surfaces, such as computer keyboards, with a household cleaner.

Staff writer Tom Avril contributed to this article.