As the coronavirus continues to spread across the United States and around the world, international leaders have taken steps to reduce movement in order to contain the virus more quickly. Public health officials have long advised Americans to stay home when sick — but in the case of coronavirus, people might carry it without ever knowing they’re infected. Can you catch coronavirus from someone with no symptoms? The answer to this question provides the rationale for social distancing.

While according to the CDC, people are most contagious when they’re showing symptoms, some spread may be possible before people display symptoms, when they’re still asymptomatic. That’s because coronavirus is primarily transmitted through respiratory droplets, says Vincent Racaniello, Ph.D, a professor of microbiology and immunology at Columbia University. Respiratory droplets are the “droplets you make when you breathe and talk and sneeze and cough — but you don’t have to be sneezing and coughing,” Racaniello says.

These respiratory droplets can travel for roughly six feet before they drop to the ground, Racaniello adds, which is why the Centers for Disease Control and Prevention (CDC) has recommended that people maintain at least six feet of distance between themselves and others. The fact that coronavirus is transmitted primarily via respiratory droplets also contributes to the virus spreading even when someone is asymptomatic.

“You can get infected from an asymptomatic person and that’s probably in part why we’re seeing such explosive spread — because you can’t isolate people who are infected,” Racaniello says. He notes that the 2003 SARS outbreak, which was caused by a different coronavirus, took a different route. “The vast majority of those infections made you very sick, so it was clear who was infected, and many of them went in the hospital where they could control the infections.”

But the 2019 coronavirus is different, Racaniello says, because of spread among asymptomatic and mildly infected people. “80% of the infections are mild, you wouldn’t even seek medical help, you wouldn’t know to quarantine yourself,” Racaniello says, “so that is a problem and that’s what’s driving the spread of this virus.”

So, people without symptoms may actually be the highest risk for spreading the disease. “There is good evidence to suggest that people with no symptoms can transmit the virus,” adds Karen Levy, Ph.D, MPH, an environmental microbiologist and epidemiologist and associate professor of environmental health at Emory University’s Rollins School of Public Health. “And in fact, that they might be the most infectious in the period before symptoms appear.”

There are measures the CDC recommends to protect yourself, including social distancing, which entails limiting or eliminating all non-essential outings, maintaining at least six feet of distance from others, avoiding restaurants and bars, and staying away from elderly relatives or neighbors. Peter Palese, Ph.D, chair of the Microbiology Department at Mt Sinai’s Icahn School of Medicine, also affirms the value of these measures. “In the absence of vaccines and antivirals,” Palese tells Elite Daily, “social distancing, quarantining and isolating people are the only measures against the virus we have.”

“One can catch the virus outdoors, if one comes close enough to a person who has been infected,” Palese adds. This has been a prominent question on people’s minds: Can you go outside if you are practicing effective social distancing? As Racaniello points out, people still need to go outside for essentials like groceries or medication. But given that you don’t know who might have been exposed to the coronavirus, especially if they are asymptomatic, Racaniello recommends avoiding contact with others as much as possible.

“You can be walking around without any apparent illness or with a mild illness, that you think might be flu or a common cold, and you’re shedding virus and infecting other people,” Racaniello says, “so it’s kind of an insidious situation.”

The CDC recommends that everyone — regardless of whether their cities and states have imposed shelter-in-place orders — continue practicing basic hygiene, such as washing your hands for at least 20 seconds, avoiding touching your face, staying home when sick, and regularly disinfecting high-touch surfaces.