Surfaces? Sneezes? Sex? How the Coronavirus Can and Cannot Spread

What you need to know about how the virus is transmitted.





The rose and yellow spheres are viral particles, which came from a coronavirus sample collected from one of the first cases in the United States.


A delicate but highly contagious virus, roughly one-900th the width of a human hair, is spreading from person to person around the world. The coronavirus, as it’s known, has already infected more than 200,000 people in 140 countries.

Because this virus is so new, experts’ understanding of how it spreads is limited. They can, however, offer some guidance about how it does — and does not — seem to be transmitted.

If I cross paths with a sick person, will I get sick, too?
You walk into a crowded grocery store. A shopper has the coronavirus. What puts you most at risk of getting infected by that person?

Experts agree they have a great deal to learn, but four factors are likely to play some role: how close you get; how long you are near the person; whether that person projects viral droplets on you; and how much you touch your face. (Of course, your age and health are also major factors.)

Also, the larger the number of people in the store — or in any other situation — the greater the chance that you’ll cross paths with an infected person, which is why so many health officials are now urging people to avoid crowds and to cancel gatherings large and small.

What’s a viral droplet?
It is a droplet containing viral particles. A virus is a tiny codependent microbe that attaches to a cell, takes over, makes more of itself and moves on to its next host. This is its “lifestyle,” said Gary Whittaker, a professor of virology at the Cornell University College of Veterinary Medicine.

A “naked” virus can’t go anywhere unless it’s hitching a ride with a droplet of mucus or saliva, said Kin-on Kwok, a professor at the Jockey Club School of Public Health and Primary Care at the Chinese University of Hong Kong.

These mucus and saliva droplets are ejected from the mouth or the nose as we cough, sneeze, laugh, sing, breathe and talk. If they don’t hit something along the way, they typically land on the floor or the ground. When the virus becomes suspended in droplets smaller than five micrometers — known as aerosols — it can stay suspended for about a half-hour, research suggests.

To gain access to your cells, the viral droplets must enter through the eyes, the nose or the mouth. Some experts believe that sneezing and coughing are most likely the primary forms of transmission. Professor Kwok said talking face-to-face or sharing a meal with someone could pose a risk.


Julian Tang, a virologist and a professor at the University of Leicester in England who is researching the coronavirus with Professor Kwok, agreed.

“If you can smell what someone had for lunch — garlic, curry, etc. — you are inhaling what they are breathing out, including any virus in their breath,” he said.

The virus does not linger in the air at high enough levels to be a risk to most people. But the techniques health care workers use to care for sick people can generate high levels of aerosols. This is part of why it’s so important that they have proper protective equipment.

How close is too close?
The Centers for Disease Control and Prevention recommends keeping a distance of six feet from other people to minimize the possibility of infection. (A useful way to think about six feet is that it’s roughly twice the length of the average person’s extended arm.)

Three feet is the distance the W.H.O. emphasizes as particularly risky when standing near a person who is coughing or sneezing.

Still, other public health experts say that at this crucial moment, when the world still has an opportunity to slow the transmission of the coronavirus, any number of feet is too close. By cutting out all but essential in-person interactions, we can help flatten the curve, they say, keeping the number of sick people to levels that medical providers can manage.

How long is too long to be near an infected person?
It’s not yet clear, but most experts agree that more time equals more risk.

Will you know a person is sick?

Not necessarily.

Fever, coughing, chest pain and shortness of breath may signal that someone has been infected with the coronavirus. (Covid-19 is the name for the disease caused by the virus.)

But it has become increasingly clear that people without symptoms can also infect others. In some cases, these people may later feel terrible enough to try to get tested, isolate themselves, seek treatment and notify friends and colleagues about potential risk. In still other cases, people with the virus may never experience the physical discomfort that would tip them off to the fact that they have been a danger to others.





Workers disinfecting subway cars in Tehran on Tuesday. The coronavirus is a delicate microbe that is killed easily with disinfectant.

Can the virus last on a bus pole, a touch screen or other surface?
Yes. After numerous people who attended a Buddhist temple in Hong Kong fell ill, the city’s Center for Health Protection collected samples from the site. Restroom faucets and the cloth covers over Buddhist texts tested positive for the coronavirus, the agency said.

This coronavirus is just the latest of many similarly shaped viruses. (Coronaviruses are named for the spikes that protrude from their surfaces, which resemble a crown or the sun’s corona.)

A recent study of the novel coronavirus found that it could live for three days on plastic and steel. If you are ordering lots of supplies online, you may be relieved to know that the virus did poorly on cardboard — it disintegrated over the course of a day. It survived for about four hours on copper.

Whether a surface looks dirty or clean is irrelevant. If an infected person sneezed and a droplet landed on a surface, a person who then touched that surface could pick it up. How much is required to infect a person is unclear.

But as long as you wash your hands before touching your face, you should be OK, because viral droplets don’t pass through skin.


Also, coronaviruses are relatively easy to destroy. Using a simple disinfectant on a surface is nearly guaranteed to break the delicate envelope that surrounds the tiny microbe, rendering it harmless, Professor Whittaker said.




Passengers on a bus in Seoul, South Korea. If an infected person sneezed and a droplet landed on a surface, a person who then touched that surface could pick it up, experts said.

Does the brand or type of soap you use matter?
No, several experts said.

My neighbor is coughing. Should I be worried?
There is no evidence that viral particles can go through walls or glass, said Dr. Ashish K. Jha, director of the Harvard Global Health Institute.

He said he was more concerned about the dangers posed by common spaces than those posed by vents, provided there is good air circulation in a room.

An infected neighbor might sneeze on a railing and if you touched it, “that would be a more natural way to get it from your neighbor,” he said.

Can I get it from making out with someone?
Kissing could definitely spread it, several experts said.

Though coronaviruses are not typically sexually transmitted, it’s too soon to know, the W.H.O. said.


Is it safe to eat where people are sick with the coronavirus?
If a sick person handles the food or it’s a high-traffic buffet, then risks cannot be ruled out — but heating or reheating food should kill the virus, Professor Whittaker said.

Dr. Jha concurred.

“As a general rule, we haven’t seen that food is a mechanism for spreading,” he said.





Waiters in February at a restaurant in St. Mark’s Square in Venice, which would usually be full of tourists.

Can my dog or cat safely join me in quarantine?
Thousands of people have already begun various types of quarantines. Some have been mandated by health officials, while others are voluntary and primarily involve staying home.

Can a cat or dog join someone to make quarantine less lonely?

Professor Whittaker, who has studied the spread of coronaviruses in animals and humans, said that he had seen no evidence that people who have the virus could be a danger to their pets.

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