The agency is the model for the much smaller European Center for Disease Prevention and Control, as well as similar agencies in Africa and around the globe. It played a major role in eradicating smallpox, as well as the near-elimination of polio. Globally, it won acclaim for helping fight AIDS, Ebola and Zika.

“Almost every major outbreak has seen the United States step up and lead, and we’re seeing exactly the opposite with President Trump,” said Lawrence O. Gostin, director of the WHO Collaborating Center on National and Global Health Law at Georgetown University.

The CDC has become a “nonentity” in the coronavirus fight, said Ilona Kickbusch, a WHO adviser and founder of the Global Health Centre at the Graduate Institute of Geneva.

“It was a highly professional, trusted organization, and they’re gone basically,” she added. “It’s a tragedy for global health.”

While Trump has attacked the WHO for bowing to Beijing, diplomats and public health workers say it’s more of a case of China stepping in to fill the void left by the U.S. retreat from the leadership role it has played for decades under Democratic and Republican presidencies alike.

Trump’s broader retrenchment from a sense of “global mission and interconnectedness with the rest of the world” has trickled down to the CDC, said Helene Gayle, a philanthropy executive and 20-year veteran of the agency who played an influential role in its fight against HIV/AIDS.

The “CDC is seen as an incredibly important institution, not just for America but for the world,” she added. “There is a void, when you have an organization that people have looked to that is not providing the kind of global leadership that it once did.”

The U.S. Congress has generally blocked Trump’s repeated attempts to cut the CDC — including an effort to slash its international work from 49 countries to 10. However, the administration has nonetheless pulled back: CDC staff numbers in China have decreased from 47 to 14 over the past two years, Reuters reported.

“Normally, CDC would be at the forefront of the response in this type of situation, both nationally and globally,” said Tom Frieden, Barack Obama’s CDC director, widely credited with helping turn around the Ebola epidemic after a flat-footed response by countries around the world, as well as the WHO.

“We’d be in a much better place if CDC was free to do what it does best: figure out how the infection is spreading and how best to reduce the spread, through technical guidance, partnerships and tools,” he said.

Since the outbreak of the coronavirus epidemic, Trump has stymied efforts to cooperate globally. At a meeting in late March, for example, G-7 foreign affairs chiefs meeting over videoconference agreed on the need for coordination. But they failed to deliver an actual accord after U.S. Secretary of State Mike Pompeo took a hard line on calling the germ the “Wuhan virus.”

That’s in sharp contrast to Obama, who addressed a U.N. summit devoted to the West Africa Ebola outbreak in 2014. Saying that a U.S. military operation was up and running in Liberia, Obama promised the world could “count on America to lead, and that we will provide the capabilities that only we have, and mobilize the world the way we have done in the past in crises of similar magnitude.”

Still, Obama stressed, the response wasn’t moving fast enough, and he urgently called on others to help: “Do not stand by, thinking that somehow, because of what we've done, that it's taken care of.”

Under Trump, “we haven’t seen the administration pulling together world leaders to say, ‘Let’s have a coordinated strategy,” said Matthew M. Kavanagh, an assistant professor of global health at Georgetown University.

Instead, the U.N. is playing that role, he added, “and getting silence from the United States.”

Until Tuesday, the U.S. was the largest contributor to the WHO, way ahead of other donors. In 2018, Washington contributed over $400 million to the WHO’s programs, or nearly 20 percent of the WHO's revenue for its programs.

When it came to the coronavirus crisis, however, the U.S. was far less generous. Washington snubbed the WHO’s urgent appeal for more funding in February, with Trump asking for $2.5 billion from Congress, none of which appeared to be going to the WHO. Eventually, it coughed up a meager $15 million, compared with over $47 million from Japan and $28 million from Germany.

The big question for David Heymann, an epidemiologist who headed the global response to SARS in 2003, is what funding Trump is threatening to cut now. The majority of the U.S. government’s funding (more than $250 million in 2018-19) is earmarked for specific programs.

If, for example, the suspended funding is taken from the health emergencies program that is currently financing the response to the coronavirus pandemic, of which the U.S. contributed 34 percent in 2018-19, the WHO would need to urgently reassess its spending.

“The U.S. has been a longstanding and generous friend to WHO, and we hope it will continue to be so,” said WHO chief Tedros Adhanom Ghebreyesus on Wednesday.

EU governments are decrying Trump's move. But so far, they don't seem eager to fill the gap.

While Germany’s Development Minister Gerd Müller told Reuters on Wednesday that the country would increase its funding to the WHO, the government’s spokesperson later refused to confirm that this would happen. Instead, the spokesperson said Germany would “continue in supporting and funding the WHO.”

Likewise, France didn’t promise any extra cash. Rather, a spokesperson for the government said it regretted Trump’s decision and that the French government “hope very much that things will go back to normal swiftly.”

China also reiterated its support for the WHO on Wednesday, with foreign ministry spokesperson Zhao Lijian expressing “serious concerns” about the U.S. decision and urging it to fulfill its obligations, according to Bloomberg.

One unlikely player offered to help: Finland. The Nordic country’s contribution appears to be largely symbolic, however, at €1 million, as well as increasing its annual funding to 2015 levels (€5.5 million), reported YLE.

While Trump’s move to defund the WHO has found few fans outside the U.S., not everybody disagrees with his underlying complaints.

Trump’s suspension of funding is “reckless and dangerous,” said David McCoy, professor of global public health at Queen Mary University of London. “But it is in keeping with Trump’s worldview and provides a way to deflect attention away from his own failings in managing Covid-19.”

McCoy conceded that there could be some truth in allegations that China was not as open as it should have been in the early stages of the outbreak.

There are also concerns that China refused offers for help, with CDC Director Robert Redfield telling American radio service SiriusXM that he offered to send a large team to China at the start of the outbreak. “Everyone was on board,” said Redfield. Despite this, the offer was rejected by the higher echelons of the Chinese government, he said.

Others even admit that Trump could be right about the WHO’s deferential position toward China.

“China has a disproportionately large influence on the WHO,” conceded Wim Groot, professor of health economics at Maastricht University.

The trouble is that with its retreat from global institutions, Washington will have more trouble making its case.

The U.S., Gostin fears, has ceded its influence.

“Nobody will trust America anymore," he said. "Not on this.”

Judith Mischke, Elisa Braun and Carlo Martuscelli contributed reporting.