GENEVA/ZURICH (Reuters) - A sharp upward revision in China’s coronavirus death toll on Friday was “an attempt to leave no case undocumented” after medical services in Wuhan were overwhelmed at the start of the outbreak, the World Health Organization (WHO) said.

FILE PHOTO: A logo is pictured on the headquarters of the World Health Organization (WHO) ahead of a meeting of the Emergency Committee on the novel coronavirus (2019-nCoV) in Geneva, Switzerland, January 30, 2020. REUTERS/Denis Balibouse

Nearly 1,300 people who died of the coronavirus in the Chinese city of Wuhan, or half the total, were not counted in death tolls because of lapses, state media said on Friday, but Beijing dismissed claims that there had been any kind of cover-up.

U.S. President Donald Trump has suggested that China has understated its toll of coronavirus deaths, and has condemned the WHO for the support it has given to China’s approach in the crisis. He suspended funding to the U.N. agency this week.

The virus has infected more than two million worldwide and killed 150,000, according to a Reuters tally.

Maria van Kerkhove, a WHO epidemiologist who took part in an international mission to China in February, said of China’s revised figures: “This was done in attempt to leave no case undocumented.”

She said the Chinese authorities had gone back over data from funeral services, care homes, fever clinics, hospitals and detention centres, and patients who had died at home, in Wuhan, Hubei province where the outbreak began late last year.

“What they have reported is that the discrepancies in these cases were due to a number of factors. First is that the health care system in Wuhan was overwhelmed at one point. And some patients died at home,” van Kerkhove said.

“Secondly is that medical staff were delayed in reporting of these cases because they were focused on providing care for those patients and they didn’t fill out the forms in time,” she said.

Mild cases were treated in makeshift hospitals in Wuhan stadiums or other facilities, van Kerkhove said, adding: “In those situations the reporting wasn’t done in a timely manner and so those cases were added.”

It was important to know the number of people who had died from the disease and to have “accurate reporting”, which can be a challenge during an outbreak, she said.

“I would anticipate that many countries are going to be in a similar situation where they will have to go back and review records and look to see did we capture all of them,” she said.

Dr. Mike Ryan, WHO’s top emergencies expert, said: “It is important that countries provide that data as quickly as they can in the interest of moving our collective efforts forward to control this pandemic.”

The virus is believed to have originated among wild animals on sale in a seafood market in Wuhan that has been closed since January. A common sight across Asia, wet markets traditionally sell fresh produce and live animals, such as fish, in the open air.

Any wet markets allowed to reopen after lockdowns must conform to stringent food and hygiene standards, WHO Director-General Tedros Adhanom Ghebreyesus said.

“Governments must rigorously enforce bans on trade of wildlife for food,” he said.