Maria Van Kerkhove, head of the World Health Organization's emerging diseases and zoonosis unit, speaks during a press conference following an emergency committee meeting over the new coronavirus in Geneva on Jan. 22, 2020.

"This was done in an attempt to leave no case undocumented," Dr. Maria Van Kerkhove, the WHO's lead scientist on Covid-19, said at a news briefing from the agency's Geneva headquarters. "They looked at the funeral service systems. They looked at hospital systems. They looked at laboratories to see if there were any duplications or if there were any cases missing."

The World Health Organization said Friday that China revised its Covid-19 infection counts "to leave no case undocumented" and that other countries will also likely need to amend their own data as systems around the world are overwhelmed.

Reporting the true number of deaths caused by Covid-19 is crucial to understanding the virus, Van Kerkhove said. Without accurate reporting of cases and deaths, epidemiologists struggle to calculate the rates of infections and fatalities, which can be used to guide government response.

U.S. economists and politicians have previously questioned the accuracy of China's coronavirus figures. China's National Health Commission has reported a total of 82,692 cases and 4,632 deaths, which is dwarfed by figures in the U.S. and some European countries, including Spain and Italy.

"It is very important to know the numbers of people who have died from Covid-19 because this is of public health importance and it is important that we have the accurate reporting of this," Van Kerkhove said.

Early in the outbreak, as White House officials, including economic advisor Larry Kudlow, raised questions about China's numbers, the WHO repeatedly defended China and the country's transparency regarding the outbreak. On Tuesday, U.S. President Donald Trump announced he was suspending funding to the WHO, criticizing them for accepting China's reporting as accurate.

"The WHO willingly took China's assurances at face value, and they willingly took it at face value and defended the actions of the Chinese government even while praising China for its so-called transparency," Trump said Tuesday. "I don't think so."

China state news agency Xinhua posted a notice Friday from Wuhan's municipal government, which explained the discrepancies in the city's data.

First, the notice said a surge of patients in the early stage of the outbreak caused a shortage of medical resources and inadequacy in the city's treatment capacity. That resulted in some patients dying at home

In addition, hospitals were overwhelmed, which resulted in delayed, missing or erroneous reporting of cases and deaths, according to the notice.