China’s killer outbreak: key questions answered

What is a coronavirus? Coronaviruses are a large family of viruses that cause illnesses ranging from the common cold to more severe diseases such as severe acute respiratory syndrome (Sars).

The viruses are zoonotic, meaning they are transmitted between animals and people, the WHO says.

The first cases identified were among people connected to the Huanan Seafood Wholesale Market in Wuhan.

Experts have also identified cases where it is believed to have spread through human-to-human transmission.

Symptoms include fever, cough, tightness of the chest, shortness of breath and breathing difficulties.

More severe cases can cause pneumonia, severe acute respiratory syndrome, kidney failure and death.

There are no specific treatments for a new coronavirus but symptoms can be treated.

What is known about the source of the virus?

Experts and clinicians still do not know the source of the virus, and some say it may never be identified.

Paul Hunter, professor in medicine at Norwich Medical School, University of East Anglia, believes the virus has been detected in bats and snakes prior to this outbreak, and the strains in both are similar to each other and to the strains from human cases.

Prof Hunter adds that the strains found in humans are more like the strains found in snakes, so that is more likely, but still not proven. Ideally the virus would be isolated from food animals, but it is likely that the infected batch of animals is long gone.

Prof Hunter said that cooked food is unlikely to be the source, suspecting that the most likely transmission pathway would be from aerosols produced during handling of the live animals and during butchery and food preparation.

These would then be inhaled or contaminate surfaces that could be touched by people.

He adds that raw food is also a risk.