The new coronavirus, now known as Covid-19, was first encountered in Wuhan, China, in December 2019.
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. China’s national health commission has confirmed human-to-human transmission of the virus.
The virus causes 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 antiviral drugs we have against flu will not work. If people are admitted to hospital, they may get support for their lungs and other organs, as well as fluids. Recovery will depend on the strength of their immune system. Many of those who have died were already in poor health.
New and troubling viruses usually originate in animal hosts. Ebola and flu are other examples, and severe acute respiratory syndrome (Sars) and Middle Eastern respiratory syndrome (Mers) are both caused by coronaviruses that came from animals. In 2002, Sars spread virtually unchecked to 37 countries, causing global panic, infecting more than 8,000 people and killing more than 750. Mers appears to be less easily passed from human to human, but has greater lethality, killing 35% of about 2,500 people who have been infected.
We don’t yet know how dangerous Covid-19 is, and we won’t know until more data comes in. The mortality rate seems to be about 2%. For comparison, seasonal flu typically has a mortality rate below 1% and is thought to cause about 400,000 deaths each year globally. Sars had a death rate of more than 10%.
Another key unknown, of which scientists should get a clearer idea in the coming weeks, is how contagious Covid-19 is. A crucial difference is that unlike flu, there is no vaccine for the new coronavirus, which means it is more difficult for vulnerable members of the population – elderly people or those with existing respiratory or immune problems – to protect themselves. Hand-washing and avoiding other people if you feel unwell are important. One sensible step is to get the flu vaccine, which will reduce the burden on health services if the outbreak turns into a wider epidemic.
The name Covid-19 was announced on 11 February by the World Health Organization. The director general, Tedros Adhanom Ghebreyesus, said: “We had to find a name that did not refer to a geographical location, an animal, an individual or group of people, and which is also pronounceable and related to the disease. Having a name matters to prevent the use of other names that can be inaccurate or stigmatising.”