But the true mortality rate could be as low as one per cent if all mild and asymptomatic cases are taken into account, researchers say.
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 there.
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.
Dr Lucy Okell, a lecturer in mathematical modelling at Imperial, said it was critical to work out the chance of dying from the coronavirus and who was most at risk of disease.
“Deaths tend to be reported promptly but there is less information on how many people have recovered from the virus. We are likely to be missing cases who have milder symptoms but there is limited information on how common these are,” she said.
Official data shows that nearly 3,500 people have recovered from the disease but it is not known how severe these cases were.
Dr Bharat Pankhania of the University of Exeter Medical School said: “During an evolving outbreak, there will be many more people with mild symptoms, not requiring any medical intervention. These people will also be unlikely to go to their doctors.
“Thus, mild illness or illness with minimal symptoms, lack of doctors and lack of resources to go to the doctor could all add up to the true extent of the number of people infected being significantly higher than current estimates.”