“There’s no question that China’s bold approach to the rapid spread of this new respiratory pathogen has changed the course of what was a rapidly escalating, and continues to be, deadly epidemic,” Bruce Aylward, the Canadian epidemiologist who led the team, said on Monday.

China on Tuesday reported 508 new cases of the pneumonia-like illness, but only nine were outside Hubei, suggesting extreme measures to limit the spread of the virus had been effective in containing the epidemic to within the central province where it began.

According to the National Health Commission, 499 of the new mainland cases were reported in Hubei, and 464 of those were in Wuhan.

In the weeks since the virus began spreading across China, the WHO has fielded questions about its support for China’s aggressive efforts to contain the epidemic, and the exclusion of Taiwan from meetings about the outbreak.

Taiwan has been excluded from the organisation in recent years following pressure from Beijing, which claims Taiwan as part of its territory.

For the WHO mission to China, there was also a delay of about two weeks between the trip being confirmed and the team being finalised after WHO Director General Tedros Adhanom Ghebreyesus met Chinese President Xi Jinping in Beijing in late January.

US officials said earlier that their experts had not been invited into China, but two American specialists were later confirmed to be part of the delegation.

The joint mission also initially did not include Wuhan, which some experts said added to concerns that the Chinese government was not being fully transparent.

An online petition calling for Tedros’ resignation for being too deferential to Beijing had garnered some 400,000 signatures as of Tuesday.

“I know there is a lot of pressure on WHO when we appreciate what China is doing, but because of pressure, we should not fail to tell the truth,” Tedros said in response to the criticism.

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“We should tell the truth and that’s the truth. China doesn’t need to ask to be praised, and I don’t expect any country wants to be, asks to be praised. It was not, it is not, that’s the truth, the whole truth.”

Analysts said China’s interactions with the WHO had improved during the coronavirus outbreak compared to the severe acute respiratory syndrome (Sars) epidemic of 2002-03, when the WHO’s offer to send an investigation team to the outbreak epicentre of Guangzhou was initially rejected.

“But then as it became clear that this is not China’s outbreak, and when the leaders realised that international cooperation was crucial to stem the virus, they became more accommodating of international support,” said Yanzhong Huang, a senior fellow for global health at US think tank the Council on Foreign Relations.

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The WHO and China have a long history of cooperation, reflected in part by the appointment of Hong Kong doctor Margaret Chan Fung Fu-chun as director general of the global health body, a role she held from 2007 to 2017.

Chan was the first Beijing representative to lead the WHO, and after her second term she became a member of political advisory body the Chinese People’s Political Consultative Conference.

Tedros also visited Beijing in July 2018, where he met Foreign Minister Wang Yi, saying ahead of the visit there was “unlimited potential and a window of opportunity for WHO and China to advance a new era of strategic partnership on global health”.

Katherine Mason, author of Infectious Change: Reinventing Chinese Public Health After an Epidemic and a professor at Brown University, said members of the public health community in China wanted to cooperate and have a good relationship with the WHO.

“They certainly recognise that they need some help with this situation,” she said. “However, Chinese officials cannot be made to share anything that they do not want to share or feel they cannot share. They will be managing what they say and do very carefully, I am sure.”

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Mason said the Sars epidemic had led to a major remodelling of China’s public health system with the aim of preventing a similar type of crisis from happening again, including developing a surveillance and reporting system for local health officials.

The government response to the new coronavirus had been faster and more intense than during Sars, and it had made a “bigger effort to cooperate more thoroughly with the global health community”, she said.

But the local health reporting systems still faced challenges from the “large disincentives” for officials to report diseases, given that “new viruses are still officially state secrets”, she said.

Arnold Monto, a professor with the University of Michigan’s epidemiology department, said a lot had changed in China since Sars, with Beijing taking a “very aggressive approach” to limit the spread of the new virus.

The WHO mission aimed to understand the effectiveness of China’s containment measures, and the severity and transmissibility of the disease, he said.

“The WHO is an international organisation – their major mission is international to prevent the spread outside of a particular country because a particular country has the right to do what they want in their own country, so it’s a question of trying to learn lessons,” he said.

“If there is a request for help from the WHO, they will give it to a particular country, but that usually happens in countries that don’t have the wherewithal that China has.”