Imagine you're riding public transport to school or work and the man across the aisle erupts in a sneeze that explodes into the air. Halfway down the car, someone else coughs uncontrollably. Neither cover their mouth or nose.
The woman next to you is wearing a surgical mask, but you are not.
Are you doomed to get sick?
Experts say yes. And no.
Viruses -- like the coronavirus outbreak that started in Wuhan, China, recently and has migrated around the globe -- typically ride on aerosolized droplets, meaning the stuff that comes out of your nose and mouth when you cough and sneeze, explained Dr. Donald Milton, who directs the Maryland Institute for Applied Environmental Health.
Milton studies airborne viruses and heads the University of Maryland response team to students returning to school from China and other international travel. While surgical masks are advised -- particularly the N95 particulate respirator mask -- they do not offer complete coverage.
The U.S. government warns that masks do not "filter or block very small particles in the air that may be transmitted by coughs, sneezes or certain medical procedures."
And masks can't prevent droplets from getting into your eyes, Milton said.
"I like to describe [it] as getting hit with a ballistic droplet in the eye," he said.
Social media has been sharing hashtag #coveryourmouth, admonishing people to use the crook of their arm, a handkerchief or a tissue to block the spew of aerosolized germs in public places.
And then there are the railings, seats, doors and myriad handles that people routinely touch moving in and out of subways, classrooms, shops and at home after also touching their faces, noses and mouths.
"Door knobs are a favorite suspect," Milton said. So handwashing (include the wrists and lower arms, health officials say) and disinfecting are key.
Millennial Doktora (@MillennialMD) tweeted a public service announcement Jan. 21, around the time the coronavirus outbreak began to make news.
"1. Wash your hands frequently. Use rubbing alcohol if this is not possible. 2. Cover your mouth when sneezing or coughing and then wash your hands. 3. Use face mask if you have cough. 4. Stay away from the young, elderly, pregnant, & cancer patients if you have [upper respiratory tract infection] symptoms," she tweeted. "5. Don't kiss babies!!! Not even their hands and feet. And wash your hands before and after touching a baby. 6. Teach young kids coughing and sneezing etiquette and handwashing technique especially when they go to school. 7. Drink your water, eat your fruits and veggies."
While surgical masks are not so unusual in Asian countries, they are conspicuous in Western ones where people might be reticent to use them, reported Japan Today in a story about surgical masks in 2017. "
In the UK, nobody would wear a mask like this unless they were very, very sick, or there was otherwise something terribly wrong afoot," Japan Today reported. The article also cited an incident where locals in a seaside English town thought Japanese tourists wearing masks might be terrorists.
Frequent traveler Francesca Domenella said, at her father's urging, she started wearing a surgical mask after returning from China Jan. 12. The Italian aerospace engineer, working as a risk engineer for a global commercial insurance company, found a mask in a stylish black that is washable.
In Europe, surgical masks are not common so I was expecting people to give me weird looks, which they do as soon as they realize I am not Asian," Domenella, who was traveling through Germany on her way to London, told VOA in an email. "People sneeze, cough all the time and it's better to have it. I am wearing it now too. ... Makes me feel like wearing an accessory rather than a device."
The populations most at risk of contracting the virus are the elderly, the very young and those with compromised immune systems.
Milton said the college-age population of healthy young adults is less likely to get sick.
Early screening and identification, isolation and treatment are key to controlling the spread of the virus, he said. Among the more than 1 million international students in the U.S., more than 300,000 are Chinese. The U.S. universities with the largest Chinese-student populations are in New York, California, Massachusetts, Illinois and Indiana.
"We can handle this. It depends on early detection," he said from the University of Maryland, which enrolls about 2,000 Chinese students.