The death rate for patients hospitalised with the coronavirus at the epicentre of the outbreak is nearly 20 per cent, according to new estimates. But the researchers at Imperial College, London say the overall mortality rate is likely to be much lower - one per cent - because only the most severe cases of the disease in China are being tested. The study found that the case fatality rate for patients diagnosed with the disease in the Chinese city of Wuhan – where the outbreak emerged at the end of last year – is 18 per cent, but they warn that there is “high uncertainty” with this figure. The estimates were published as the latest figures show that more than 40,000 people have fallen ill with the disease worldwide and more than 900 people have died. Eight people in the UK have been admitted to hospital after testing positive for the virus – and five Britons have been hospitalised in France, after falling ill at the French ski resort of Contamines-Montjoie.

The study found that the overall death rate from the disease outside China is probably around one per cent. Because many countries have been looking for cases of the coronavirus – known as 2019-nCov – they have tested people with a range of respiratory symptoms, some of which will be mild. In China only people with pneumonia are being tested so only the severe cases are being picked up, which explains the higher death rate here. The Imperial College researchers estimate that 1.3 per cent of people in Wuhan had the infection on January 31 but, comparing this figure with confirmed cases, they believe that only one in 19 of these people are being tested for the disease. They call for further research into mild cases of the disease to determine a more accurate case fatality rate.

Neil Ferguson, professor of mathematical biology at Imperial College, said the new coronavirus was similar to the influenza pandemics of the 20th century. H1N1 – or swine flu – which swept around the world in 2009 had a death rate of around 0.02 per cent, researchers found. “Understanding the likely impact of the unfolding pandemic caused by the 2019-nCov virus on human health will be critical to informing the decisions made by countries in the coming weeks on how best to respond to this new public health threat,” he said. “Our estimates – while subject to much uncertainty due to the limited data currently available – suggest that the impact of the unfolding epidemic may be comparable to the major influenza pandemics of the 20th century,” he said.