An outbreak of a newly recognized coronavirus in the Chinese city of Wuhan is making international headlines. Already hundreds of people have been sickened and more than 100 have died as a result of the illness. Additional coronavirus patients have been found in Hong Kong, Taiwan, Japan, South Korea and the United States.

We have seen outbreaks like this involving newly emerged diseases like SARS, MERS, Zika and Swine flu. Is this one different? We sat down with Andrew Pavia, M.D., the chief of the Division of Pediatric Infectious Diseases for University of Utah Health who studies emerging infections to learn more.

What is a coronavirus?

Coronaviruses are a large and diverse group of viruses that infect animals and humans. They are named after their crown-like appearance when viewed with an electron microscope. The greatest number of known coronaviruses infect animals, but until recently, six were known to infect humans. Four types, called HKU1, NL63, 229E and OC43 tend to cause mild cold-like illness though more severe illness can occur, especially with HKU1.

Coronaviruses are of great interest because of the potential for animal viruses to “spill over” into human populations. We gained a new respect for coronaviruses when SARS virus (Severe Acute Respiratory Syndrome) emerged in southern China and then spread to more than three dozen countries and sickened more than 8,000 people, killing 774. SARS virus—unlike the human coronaviruses—tended to cause severe acute respiratory illness (hence the name). SARS virus turned out to be a bat coronavirus that had not previously been known to infect humans. It may have reached people through exposure to an intermediate host, probably civet cats in live markets.

The sixth coronavirus to infect humans is the MERS virus (Middle Eastern Respiratory Syndrome) that emerged in Saudi Arabia in 2012. It too is a bat virus and a member of the same sub-family—the beta coronaviruses—as SARS. It also causes severe disease in some people. Camels are an important intermediate host and the majority of cases are related to contact with camels, though person-to-person spread does occur.

The current outbreak that emerged in Wuhan is due to a previously unknown beta coronavirus. The closest known relative is another bat virus and it is moderately related to SARS virus. The current name for the new virus is the catchy “2019-nCoV” but virologists and epidemiologists will eventually settle on a better name. With tongue firmly in cheek, I would vote for WARS virus or “Wuhan associated respiratory syndrome,” but I doubt that will be the final choice.

How is it transmitted?

There is a lot we don’t yet know about the epidemiology of the 2019-nCoV disease, including many of the details about transmission. It is clear there is some person to person transmission. China reports that about 17 health care workers have become ill after caring for patients. It is worth pointing out that the health care workers may not have been taking appropriate protection measures such as wearing a mask, gloves and gown. All other coronaviruses are transmitted by “respiratory droplets,” which is direct contact with respiratory secretions or close exposure to droplets from coughing or sneezing. This is likely to be the way 2019-nCoV is transmitted.

An important measure epidemiologists use of how infectious an organism is the basic reproduction number (R0 or “Rnaught,” defined as the number of new infections causes by each infected person). SARS and MERS have quite low R0 meaning they are not very easily transmitted.  We still have no estimates of how contagious 2019-nCoV is but my early guess is that it is likely to be in the same range as MERS.

What are the symptoms?

Patients infected with 2019-nCoV have presented with cough and shortness of breath. Most have had a fever. Among hospitalized patients, chest X-rays often show pneumonia. There appears to be a range of symptoms, from quite mild to severe. Seventeen deaths have occurred among some 700 confirmed cases, but it is notoriously difficult to accurately determine the mortality rate early in an epidemic since the severe cases and deaths are more likely to be diagnosed and reported. It does appear that the mortality is likely to be quite a bit lower than SARS or MERS.

Why is there so much concern about people traveling during this outbreak?

In Asia, the Lunar New Year is a traditional time to travel in order to be with friends and family. The concern is that people from Wuhan and other areas experiencing the 2019-nCoV outbreak will travel and bring the virus to many other areas.

How is this outbreak different from other outbreaks?

Every new emerging infection raises new questions and presents new challenges. In the early days, we still need answers to important questions: What is the range of severity? Are there many mild infections for every case of pneumonia? Who is at greatest risk of serious illness—is it people with medical illness and the very old? How long do ill people shed the virus? How easy is it to transmit? Will there be some people who are extremely contagious—so-called “super spreaders?”

In the longer term we want to know where the virus came from, and what changed that allowed it to spill over. We want to identify antiviral drugs to treat very ill patients and potentially develop a vaccine.

Among the critical questions: Will the virus evolve over time?

With the number of sick and dead should this be considered an international health crisis?

Labeling an outbreak “A Public Health Emergency of International Concern” is a decision made by the WHO. The decisions can be a bit hard to fathom from the outside.

Regardless of the WHO’s ultimate decision, in the U.S. CDC is taking an aggressive stance. They are issuing frequent updates, advice for health care workers, screening people at airports and doing an extensive investigation.

How can people avoid becoming ill?

At present, people who have not traveled to China, particularly Wuhan city or Hubei province, or have been in close contact with a person known to have the new virus are at very low risk. The same precautions that protect against catching and spreading influenza and other respiratory viruses are likely to be helpful for this respiratory virus: Wash your hands regularly, avoid touching your nose and eyes, cover your mouth when you cough and sneeze and don’t go to work if ill. Millions of people in Asia wear masks in the streets during cold and flu season but there is no evidence yet that mask use in public by those who are well is effective. There is some evidence that wearing a mask when you are coughing and sneezing may protect those around you.

What should someone do if they become ill?

This time of year many viruses are circulating that cause cough and fever. Unless you have traveled to Wuhan or an area in China where 2019-nCoV you are extremely unlikely to be infected with the new coronavirus.

If you have a cough or difficulty breathing and a fever and you have traveled to Wuhan or been in close contact with a patient with a confirmed 2019-nCoV infection, you should call your doctor, clinic or Emergency Department before coming in. They will have you put a mask on immediately on arrival to reduce the chance of spread and move you to a private room.