Deadly coronavirus hasn't yet sickened anyone in Wisconsin, but a Chicago case has been confirmed. Here's what to know.

Six students in Wisconsin are being monitored for coronavirus after returning from China and a Chicago woman was diagnosed with the illness. 

It may only be a matter of time before someone in Wisconsin is infected.Here are some basic facts state residents need to know.

What is the latest coronavirus update?

On Friday, the Centers for Disease Control and Prevention confirmed a second U.S. case of the new coronavirus, this one in Chicago. Like the previous U.S. coronavirus patient, who lives in Washington state, the one in Chicago involves someone who traveled to Wuhan, a city of 11 million people in the eastern half of the country on the Yangtze River. In this latest case, a woman in her 60s was in China to care for her father. 

What is a coronavirus?

It's part of a large family of viruses that cause respiratory infections. Most coronaviruses are not dangerous, but some can be lethal. 

What are the symptoms of coronavirus?

There are four main coronaviruses that commonly circulate in the U.S. causing cold symptoms in the nose and throat.

How did this new virus start?

The new coronavirus causes a respiratory disease marked by pneumonia-like symptoms including difficulty breathing. It began to appear in late December and is believed to have originated at the Huanan Seafood Market in Wuhan, a so-called "wet market" at which seafood and meat are sold alongside live animals. It's not uncommon for animals to be slaughtered in front of customers. The market was closed Jan. 1.

The disease is believed to have jumped from animals to humans, and new cases — involving people who did not visit the market — suggest the virus is now spreading person to person. Because the virus is new, humans have not had a chance to build up immunity to it. At present there is no standard treatment or cure.

How many have been affected?

The virus, which broke out in Wuhan last month, has infected at least 1,975 people in at least 29 provinces and cities and killed 56 people in China, according to the National Health Commission.

A host of Asian countries have confirmed cases: Japan, South Korea, Taiwan, Vietnam, Nepal, Thailand and Singapore. Like the United States, two cases have been confirmed in France. And one case turned up in Canada Saturday.

How is the new coronavirus spread?

The virus is believed to be spread through close contact, especially coughing or sneezing, with an infected individual.

Has the disease touched Wisconsin?

At the University of Wisconsin-Platteville, a half-dozen students are under watch — not because they have shown any symptoms of the new virus, but as a precaution because they all live together on campus and just returned from China, where at least two live in Wuhan. 

How can people protect themselves? 

Advice from the World Health Organization and the Centers for Disease Control and Prevention includes washing hands after coughing, sneezing, using the toilet, preparing food, or coming into contact with animals or people who are showing symptoms of illness. In general, people are advised to avoid coming close to people who appear ill.