More than 4,520 cases have been reported globally, most of them in China and especially in Wuhan and nearby cities in Hubei province.
Here is what you need to know:
What is coronavirus?
According to the World Health Organization (WHO), coronaviruses are a family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS).
These viruses were originally transmitted between animals and people. SARS, for instance, was believed to have been transmitted from civet cats to humans while MERS travelled from a type of camel to humans.
Several known coronaviruses are circulating in animals that have not yet infected humans.
The name coronavirus comes from the Latin word corona, meaning crown or halo. Under an electron microscope, the image of the virus is reminiscent of a solar corona.
A novel coronavirus, identified by Chinese authorities on January 7 and named 2019-nCoV, is a new strain that had not been previously identified in humans.
Little is known about it, although human-to-human transmission has been confirmed.
What are the symptoms?
According to the WHO, signs of infection include fever, cough, shortness of breath and breathing difficulties.
In more severe cases, it can lead to pneumonia, severe acute respiratory syndrome, kidney failure and even death.
The incubation period of the coronavirus remains unknown. Some sources say it could be between 10 to 14 days.
Some experts say it may not be as deadly as other types of coronavirus such as SARS, which killed nearly 800 people worldwide during a 2002-03 outbreak that also originated from China.
MERS, which did not spread as widely, was more deadly, killing a third of those it infected.
Where have cases been reported?
Most cases have been reported in China.
All deaths have been in China - the vast majority in Hubei province.
The virus has spread to many Asian countries, as well as Australia, Europe and North America. Nearly all of the dozens of cases outside China are among people who recently travelled from there.
What is being done to stop it spreading?
There is no vaccine for the new virus.
Chinese authorities have effectively sealed off Wuhan, state media said.
The move was meant to "resolutely contain the momentum of the epidemic spreading" and protect lives, the central city's special command centre against the virus said, according to state broadcaster CCTV.
More than a dozen other Chinese cities also adopted transport restrictions, affecting 56 million people.
Airports around the world have introduced screening measures and some countries are working to evacuate their citizens from Wuhan.
Where did the virus originate?
Chinese health authorities are still trying to determine the origin of the virus, which they say came from a seafood market in Wuhan where wildlife was also traded illegally.
The WHO also says an animal source appears most likely to be the primary source of the outbreak.
Snakes - including the Chinese krait and the cobra - may be the source of the newly discovered virus, according to Chinese scientists.
Is this a global emergency?
The outbreak does not yet constitute a global emergency, the WHO has said.
WHO chief Tedros Adhanom Ghebreyesus has said the decision to hold off on issuing the declaration used for the gravest epidemics should not be taken as a sign that the body does not think the situation is serious.
"This is an emergency in China, but it has not yet become a global health emergency," he told reporters.
There have been five global health emergencies since 2005, when the declaration was formalised - swine flu in 2009; polio in 2014; Ebola in 2014; Zika in 2016 and Ebola again in 2019.
SOURCE: AL JAZEERA AND NEWS AGENCIES