Coronaviruses are a large family of pathogens, most of which cause mild lung infections such as the common cold.
But coronaviruses can also be deadly. SARS, or severe acute respiratory syndrome, is caused by a coronavirus and killed hundreds of people in China and Hong Kong in the early 2000s.
So far, 563 people have so far died after testing positive for the virus.
What are the symptoms?
Some people who catch the Wuhan coronavirus may not have any symptoms at all, or only very mild ones like a sore throat or a headache.
Others may suffer from a fever, cough or trouble breathing.
And a small proportion of patients will go on to develop severe infection which can damage the lungs or cause pneumonia, a life-threatening condition which causes swelling and fluid build-up in the lungs.
How is it detected?
The virus’s genetic sequencing was released by scientists in China and countries around the world have used this to create lab tests, which must be carried out to confirm an infection.
Delays to these tests, to test results and to people getting to hospitals in China, mean the number of confirmed cases is expected to be just a fraction of the true scale of the outbreak.
How did it start and spread?
The first cases identified were among people connected to the Huanan Seafood Wholesale Market in Wuhan, China.
Cases have since been identified around China and are known to have spread from person to person.
What are countries doing to prevent the spread?
Countries in Asia have stepped up airport surveillance. They include Japan, South Korea, Thailand, Hong Kong, Indonesia, Malaysia and the Philippines.
Australia and the US are also screening patients for high temperatures, and the UK announced it will screen passengers returning from Wuhan.
Is it similar to anything we’ve ever seen before?
Experts have compared it to the 2003 outbreak of severe acute respiratory syndrome (SARS). The epidemic started in southern China and killed more than 700 people in mainland China, Hong Kong and elsewhere.