A coronavirus is a family of viruses which include the common cold.

But this virus has never been seen before, so it’s been called 2019-nCov, for “novel coronavirus”.

New viruses can become common in humans after jumping across the species barrier from animals.

The Sars [Severe Acute Respiratory Syndrome] outbreak of 2003 started in bats and transferred to the civet cat which passed it on to humans.Image captionQueues have been growing at hospitals in Wuhan

This new virus also causes severe acute respiratory infection.

Symptoms seem to start with a fever, followed by a dry cough and then, after a week, lead to shortness of breath and some patients needing hospital treatment.

There is no specific cure or vaccine.

Based on early information, it is believed that only a quarter of infected cases are “severe”, and the dead are mostly – though not exclusively – older people, some of whom have pre-existing conditions.

The Chinese authorities suspect a seafood market that “conducted illegal transactions of wild animals” was the source of the outbreak.