Chinese health officials have released the first details of more than 44,000 cases of new coronavirus, Covid-19, in the largest study since the outbreak began.

Data from the Chinese Centre for Disease Control and Prevention (CCDC) finds that more than 80% of the cases have been mild, with the sick and elderly most at risk.

The research also points to the high risk to medical staff.

On February 18, a hospital director in the city of Wuhan died from the virus.

Liu Zhiming, 51, was the director of the Wuchang Hospital in Wuhan – one of the leading hospitals in the virus epicenter. He is one of the most senior health officials to die so far.

Hubei, whose capital is Wuhan, is the worst affected province in China.

The report by the CCDC shows the province’s death rate is 2.9% compared with 0.4% in the rest of the country.

The findings put the overall death rate of the coronavirus at 2.3%.

China’s latest official figures released on February 18 put the overall death toll at 1,868 and 72,436 infections.

Officials reported 98 new deaths and 1,886 new cases in the past day, with 93 of those deaths and 1,807 infections in Hubei province – the epicenter of the outbreak.

According to Chinese authorities, more than 12,000 people have recovered.

The study, published in the Chinese Journal of Epidemiology on February 17, looked at more than 44,000 confirmed cases of Covid-19 in China as of February 11.

While the results largely confirm previous descriptions of the virus and patterns of infection, the study includes a detailed breakdown of the 44,672 confirmed cases across all of China.

The study finds that 80.9% of infections are classified as mild, 13.8% as severe and only 4.7% as critical. The number of deaths among those infected, known as the fatality rate, remains low but rises among those over 80 years old.

Looking at the sex ratio, men are more likely to die (2.8%) than women (1.7%).

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The research also identifies which existing illnesses put patients at risk. It puts cardiovascular disease at number one, followed by diabetes, chronic respiratory disease and hypertension.

Pointing out the risk to medical staff, the study says that a total of 3,019 health workers have been infected, 1,716 of which were confirmed cases. Five had died by February 11, which was the last day of data included in the research.

On February 13, China broadened its definition of how to diagnose people, including “clinically diagnosed cases” which previously were counted separate from “confirmed cases”.

Looking forward, the study finds that “the epidemic curve of onset of symptoms” peaked around January 23-26 before declining up to February 11.

It suggests that the downward trend in the overall epidemic curve could mean that “isolation of whole cities, broadcast of critical information  (e.g., promoting hand washing, mask wearing, and care seeking) with high frequency through multiple channels, and mobilization of a multi-sector rapid response teams is helping to curb the epidemic”.

The authors also warn that with many people returning from a long holiday, the country “needs to prepare for the possible rebound of the epidemic”.

China’s response to the new coronavirus has seen the lockdown of Wuhan – the largest city in Hubei – and the rest of the province as well as severe travel restrictions on movements across the country.