This photo taken on February 20, 2020 shows doctors looking at a lung CT image at a hospital in Yunmeng county, Xiaogan city, in China's central Hubei province. STR | AFP | Getty Images

Coronaviruses are a large family of viruses that may cause illness in animals or humans and include other severe diseases from the past like MERS and SARS. COVID-19 is the most recently discovered coronavirus and has been linked to a large seafood and live animal market in Wuhan, China, where it was first found late last year. Since then, China has taken drastic measures to contain the virus, like closing entire cities, rapidly constructing hospitals and shuttering factories and stores for weeks. According to the World Health Organization, symptoms of the disease include fever, cough, shortness of breath and breathing difficulties. In more severe cases, the infection can cause pneumonia, severe acute respiratory syndrome, kidney failure and death.

How does COVID-19 spread?

How the coronavirus spreads is similar to the flu, according to WHO. Whenever someone with the virus coughs or exhales, they release droplets of infected fluid that can land on nearby surfaces like desks, tables or telephones and can infect another person who comes in contact. Someone standing within six feet of another infected person also stands the risk of breathing in the same droplets that are exhaled or coughed out. The Centers for Disease Control and Prevention maintains that this is how the virus is thought to spread primarily.

How is COVID-19 different from the flu?

WHO officials have said that COVID-19 does not transmit, or pass on, as efficiently as the flu from the data they have on the virus so far. With the flu, people who are infected but are not yet sick are major drivers of transmission, but that does not appear to be the case with COVID-19, they said. However, COVID-19 can cause more severe illness than flu. People around the world have built up immunity to seasonal flu strains but COVID-19 is a new virus, which means more people are susceptible to infection and some will suffer severe disease, said Dr. Tedros Adhanom Ghebreyesus, WHO's director-general. While there are therapeutics and vaccines that can treat and prevent the flu, there are no vaccines or specific treatments to do the same with the coronavirus, Tedros said. Globally, about 3.4% of reported COVID-19 cases have died, Tedros said at a press conference on March 3. In comparison, the seasonal flu generally kills far fewer than 1% of those infected, he added. COVID-19's mortality rate, however, is suspected to be lower than epidemics in the past, such as MERS or SARS. And the rate is considered to be preliminary because it is unknown how many cases have gone unreported. People who are older and those with weakened immune systems or other health conditions such as diabetes, heart and lung disease are more vulnerable to serious illness from COVID-19, WHO warns. Few children appear to develop serious illnesses when infected with COVID-19, although experts warn the disease is still ongoing and that could change.

What can you do to protect yourself?