Coronaviruses, named for the crown-like spikes on their surface, are common in many different species of animals, including camels and bats.
It is rare, but some coronaviruses can evolve and infect humans and then spread between humans.
There are four types of common coronaviruses that infect people around the world causing mild illness. Symptoms include runny nose, coughing, sore throat and sometimes a fever. In most cases, you won't know whether you have a coronavirus or a different cold-causing virus, such as rhinovirus.
This new virus is one of three that can cause serious respiratory illness; the other two are SAR and MERS.
Severe acute respiratory syndrome, or SARS, was first reported in Asia in 2003. It spread to more than two dozen countries. Since 2004, there have not been any known cases of SARS reported anywhere in the world.
Middle East respiratory syndrome, or MERS, was first reported in the Arabian peninsula in 2012 and spread to several other countries including the U.S.
The last outbreak was in South Korea in 2015.
Many MERS patients developed severe respiratory illness with symptoms of fever, cough and shortness of breath. About 3 or 4 out of every 10 patients reported with MERS have died.
SARS and MERS have each led to about 800 deaths.