The new coronavirus, now known as Covid-19, was first encountered in Wuhan, China, in December 2019, and has gone on to affect over 80,000 people around the globe, causing over 2,800 deaths.
The virus can cause pneumonia. Those who have fallen ill are reported to suffer coughs, fever and breathing difficulties. In severe cases there can be organ failure. As this is viral pneumonia, antibiotics are of no use.
The mortality rate seems to be about 2%. For comparison, seasonal flu typically has a mortality rate below 1%.
Like other coronaviruses, it originated in animals and then migrated to humans. Many of those initially infected either worked or frequently shopped in the Huanan seafood wholesale market in the centre of the city, which also sold live and newly slaughtered animals.