More than 120,000 coronavirus cases have been reported worldwide, with nearly 4,400 deaths so far.
Here is what we know about the origin of coronavirus.
Where did it come from?
Coronavirus appears to have originated in a market in Wuhan, China, where live wild animals including marmots, birds, rabbits, bats and snakes are traded.
The Telegraph explains that such markets pose a “heightened risk of viruses jumping from animals to humans” because hygiene standards are “difficult to maintain if live animals are being kept and butchered on site”.
“Although an initial analysis of the virus that causes Covid-19 suggested it was similar to viruses seen in snakes, the hunt for the animal source of Covid-19 is still on,” says Wired. Bats and pangolins have also been suggested as the origin animal.
On 31 December, the World Health Organization (WHO) received the first reports of a previously unknown virus.
How did it spread?
On 11 January, Chinese state media reported the first known death from an illness caused by the virus. Within nine days, the first cases outside mainland China were confirmed, in Japan, South Korea and Thailand.
By 21 January it was apparent that the disease could be transmitted between humans.
Less than two weeks later, a 44-year-old man in the Philippines died after being infected, the first death reported outside China. According to disease-modelling experts, on average, each infected person has transmitted the virus to about 2.6 others, though the range is between 1.5 and 3.5, says The Wall Street Journal.
One of the worst outbreaks was on a cruise ship anchored off Japan. More than 700 people on board tested positive for the virus.
What might happen next?
WHO’s chief Tedros Adhanom Ghebreyesus has warned that the window of opportunity to contain Covid-19 is “narrowing”.
In the UK, the government says it is extremely likely that the virus will spread in a significant way. Measures to shut down large events might be put in place and people may be advised to work from home.