Coronavirus has spread to more than 80 countries, including the UK,reports BBC.
So, what is the disease and what can you do to protect yourself?
What are the coronavirus symptoms?
Coronavirus is a respiratory disease which seems to start with a fever, followed by a dry cough. After a week, it leads to shortness of breath and some patients require hospital treatment.
These symptoms do not necessarily mean you have the illness. They are similar to those for much more common viruses, such as colds and flu.
In more severe cases, coronavirus can cause pneumonia, severe acute respiratory syndrome, multiple organ failure and even death.
Older people, and people with pre-existing medical conditions (such as asthma, diabetes, heart disease), are more likely to become severely ill.
The incubation period - between infection and showing any symptoms - lasts up to 14 days, the World Health Organization (WHO) says. But some researchers say it may be up to 24 days.
How do I protect myself?
Regular and thorough hand washing is crucial, health agencies say.
It is not yet known exactly how coronavirus spreads. However, similar viruses are spread via droplets, such as those produced when an infected person coughs or sneezes.
So, coughing and sneezing into tissues, not touching your face with unwashed hands, and trying to avoid close contact with infected people are important.
Face masks do not provide effective protection against coronavirus, according to medical experts.
Advice for people who have travelled back to the UK from the main affected areas and some other countries, and who may need to self-isolate, has been issued.
Other countries have their own measures in place. For example, the US Centre for Disease Control and Prevention advises people showing symptoms to call their healthcare provider, and those who are mildly ill to self-isolate.
The World Health Organization has also issued advice for the public.
Thousands are still being treated but may go on to die - so the death rate could be higher. But it is also unclear how many mild cases remain unreported - so the death rate could also be lower.
To put this into context, about one billion people catch influenza every year, with between 290,000 and 650,000 deaths. The severity of flu changes every year.
Right now, treatment relies on the basics - keeping the patient's body going, including breathing support, until their immune system can fight off the virus.
However, the work to develop a vaccine is under way and it is hoped there will be human trials before the end of the year.
Hospitals are also testing anti-viral drugs to see if they have an impact.
How fast is it spreading?
Hundreds of new cases are being reported worldwide each day. However, it is thought health agencies may be unaware of many cases.
After starting in China, coronavirus is now spreading fast in countries like South Korea, Italy and Iran.