What's known and unknown about how the new coronavirus spreads

Hand-washing is still one of the best ways to keep yourself safe from viruses.
Image: Police in protective gear wait to evacuate residents from a public housing building, following the outbreak of the novel coronavirus, in Hong Kong
Police in protective gear wait to evacuate residents from a public housing building following the outbreak of the novel coronavirus in Hong Kong on Tuesday, Feb. 11, 2020.Tyrone Siu / Reuters

Breaking News Emails

Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.
SUBSCRIBE
By Erika Edwards

The alarming rate at which the new coronavirus has spread throughout China has raised concerns about how it passes from person to person.

"This outbreak is spreading much more quickly than SARS did," Dr. Anne Schuchat, principal deputy director of the Centers for Disease Control and Prevention, said Tuesday at the National Press Club in Washington. SARS, which is caused by another type of coronavirus, sickened more than 8,000 people during a 2002-03 outbreak. Nearly 800 people died before the outbreak was contained.

In contrast, the new coronavirus had infected more than 42,000 people by Tuesday afternoon — just two months after it was discovered. More than 1,000 people have died, most of them older adults with underlying health conditions.

"The breathing zone"

Infectious disease experts maintain that the vast majority of COVID-19 cases spread through close contact with an infected person. COVID-19 is the new name for the illness caused by the viral infection.

That generally means being exposed to droplets from a sick person's sneeze or cough. Those droplets can travel as far as 6 feet; outside that zone, the risk is much lower, experts say.

"That's what we call the breathing zone," said Dr. William Schaffner, a professor at Vanderbilt University who is medical director of the National Foundation for Infectious Diseases. "You may breathe in what that person has breathed out, and that will contain some virus."

The tried-and-true basics of good hand hygiene are critical to stopping spread of this and other viral infections.

"Clean your hands regularly," the World Health Organization's director-general, Dr. Tedros Adhanom Ghebreyesus, said in a briefing with journalists Tuesday.

Full coverage of the coronavirus outbreak

"Keep your distance from someone who is coughing or sneezing," he said. "And when you cough or sneeze, cover your mouth and nose with a tissue or elbow."

However, a recent study from doctors in China is raising concerns about another possible mode of transmission: contact with stool from an infected individual.

The preliminary findings showed that the virus was detected in 6 percent of stool samples from patients who were sick, prompting the researchers to recommend that measures to stop the rapid spread of the virus take it into account. Gastrointestinal symptoms have rarely been reported among COVID-19 patients.

Download the NBC News app for breaking news

Meanwhile, fear that the virus could spread through unsealed pipes has begun to take hold after people who live on different floors of an apartment building in Hong Kong were diagnosed. Officials said an unsealed pipe, which could allow for rodents or contaminated air, was found in the apartment of one of the patients.

The fears are a reminder of an incident at a different apartment complex in Hong Kong during the 2002-03 SARS epidemic, when the virus apparently spread through sewage pipes.

While scientists are still learning about how the coronavirus works, experts who study infectious diseases cautiously dismissed the suggestion that it could spread through faulty plumbing.

"The idea that something could be aerosolized through several levels of a building is probably not realistic," Lauren Sauer, director of operations for the Johns Hopkins Office of Critical Event Preparedness and Response, told NBC News.

"I have a feeling that this is not going to be anything to worry about as a normal mode of transmission," Sauer said.

The bottom line, experts said, is to take commonsense precautions and to avoid public places when sick with any viral illness.

"We have 13 cases [in the U.S.], and there may be even a little bit of limited transmission," said Schaffner. "But we're not going to have a big outbreak of coronavirus here in the United States."

"Everybody should take a deep breath, because we have an epidemic of coronavirus anxiety, which far exceeds the actual risk," he added.

Follow NBC HEALTH on Twitter & Facebook.

Associated Press, Rosemary Guerguerian, M.D. and Patrick Martin contributed.