How does coronavirus spread?

Here's what scientists and public health officials know so far.
Passengers wear protective masks to protect against the spread of the coronavirus as they arrive at Los Angeles International Airport on Jan. 22, 2020.
Passengers wear protective masks to protect against the spread of the coronavirus as they arrive at the Los Angeles International Airport on Jan. 22, 2020.Mark Ralston / AFP - Getty Images

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By Erika Edwards

Health care workers worldwide are learning in real time about the new coronavirus from China, as an increasing number of cases are being diagnosed and studied around the globe.

As of Friday morning, cases of the coronavirus swelled to well over 800 in China, the epicenter of the outbreak, and stretched into neighboring countries, as well as the United States, where one patient is being treated and a second case was confirmed by the Centers for Disease Control and Prevention Friday morning.

Although this particular virus — which appears to have originated from infected live animals sold at a market in Wuhan, China — is new, coronaviruses are not. Doctors know that these viruses in general can circulate easily among humans.

Stopping its spread

Coronaviruses "primarily spread through close contact with another individual, in particular through coughing and sneezing on somebody else who is within a range of about 3 to 6 feet from that person," said Dr. Kathy Lofy, a state health officer for Washington, where the patient with confirmed coronavirus has been hospitalized.

If an infected person sneezes or coughs onto a surface — a countertop, for example — and another person touches that surface and then rubs his or her eyes or nose, for example, the latter may get sick.

It's still unclear, however, how long the virus particles for this new coronavirus can live on surfaces.

What's more, it's unknown at what point a person with the virus becomes contagious. Health care workers are operating under the assumption that the incubation period for the illness is about 14 days, meaning that it takes roughly that amount of time for symptoms to show up after a person is infected. Scientists still do not know whether a person is infectious during the incubation period.

Infectious disease experts are hoping to glean insight into the new virus from another well-known coronavirus, the SARS virus. That coronavirus caused widespread global disease during its outbreak from 2002 to 2003.

"While we do not know all of the mechanisms of spread of the epidemic so far, there is likely spread by droplets and contaminated surfaces, and possible airborne [spread], similar to SARS," Dr. Mark Denison, a virologist at the Vanderbilt University Medical Center, said. Denison has been studying coronaviruses for more than three decades.

SARS was also spread through feces. Denison suggested the same spreading mechanism may be found in the new virus, but it's too early to know for sure.

Emerging details

Preliminary information on 41 patients who were hospitalized in Wuhan indicates a majority of those patients had a fever, cough and shortness of breath — symptoms similar to SARS.

But, "there are some important differences, such as the absence of upper respiratory tract symptoms," wrote the authors, from the China-Japan Friendship Hospital and Capital Medical University in China.

If patients don't have upper respiratory tract symptoms, such as runny nose and sneezing, it may be more difficult to spread the virus. However, it's still too early for doctors to say that this is true for all patients with the new coronavirus.

The report was published in the The Lancet on Friday.

Proper hand-washing

All of this makes proper hand-washing critical to help stop the spread of the germs. The Centers for Disease Control and Prevention recommends washing hands with soap and water before eating, after using the bathroom, and after blowing your nose, coughing or sneezing, and before and after caring for a sick friend or a family member.

The most effective way to clean hands is to wet them with clean water, then apply soap and scrub for at least 20 seconds, before rinsing and drying with a clean towel.

Hand sanitizers with at least 60 percent alcohol content may also be used, but the CDC warns they are not effective against all germs.

New virus, no immunity?

The fact that this virus is new may mean that the public may be particularly vulnerable, because there has not been time to build any immunity to it.

Key here, Denison said, is that coronaviruses do not offer what's known as cross protection. A person who had SARS in the past, for example, would not have any immunity against other coronaviruses, even though they are in the same virus group.

Meanwhile, preliminary investigations are underway at the National Institutes of Health to develop a vaccine that would target the new coronavirus, and potentially offer protection if the epidemic continues.

There is no specific medication for the illness, but that doesn't necessarily mean it's untreatable. That is, doctors can streamline supportive care for individual patients, whether they have fever, trouble breathing or other symptoms.

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