President Harry Truman signed the United States up to the World Health Organisation (WHO) in 1948 with the "hope and expectation" it would "help liberate men everywhere from the overhanging dread of preventable disease".
Last week, President Donald Trump moved to rip the US out of the UN body over its performance during the coronavirus pandemic - and the WHO announced an independent review into how it and others handled the crisis.
The Trump administration's rejection of an institution to which it has been the biggest donor is a reflection of both anger at the body's perceived closeness to Beijing and the President's revolt against multilateralism. But it has also highlighted concerns about how a health guardian created from the devastation of war and disease has become hobbled by political power plays, battles over science and unstable funding - all of them exacerbated by the urgency of the Covid-19 crisis.
Announcing the pandemic inquiry, Dr Tedros Adhanom Ghebreyesus, WHO director-general, said it should examine "whether the global health architecture is fit for purpose".
Some critics say the Geneva-based body is one structure that requires urgent reforms if it is to fulfil its mandate to promote public health and respond to emergencies.
"The sad truth is that global health is a political field, not a medical one," said Dr Tammam Aloudat, deputy executive director of the Access campaign at Medecins Sans Frontieres, the global medical charity. "Everyone will say nice stuff - and then act in their own national interests."
An escalating grab for supplies of possible coronavirus vaccines by national governments has underlined the concern.
Washington's trigger of the formal process to exit the WHO followed through on Mr Trump's threat in May to quit an organisation he has branded a "puppet of China" - an allegation the health body denies. Mr Trump's Democratic rival Joe Biden has said he will reverse the decision to leave if he wins November's presidential election.
The US leader's complaints that the WHO was too slow to respond to the growing crisis in China are echoed in the terms of the pandemic inquiry, which include a review of when the organisation was informed of the first outbreak and when it declared a health emergency.
POWER OVER MEMBERS
One recurring criticism is that the WHO has no authority to order member states to follow its instructions beyond the weak provisions of its International Health Regulations. Observers say this creates an incentive for it to avoid conflict by accentuating praise and playing down criticism - as it has generally done with China during the crisis, despite widespread concerns about the transparency of Beijing's initial response.
It also has no powers to order countries to allow access to investigate the origins of disease outbreaks - a crucial issue for Covid-19. At the weekend, more than six months after China announced the existence of Sars-Cov-2 in Wuhan, WHO officials finally headed to the country to prepare plans to identify its animal origin.
"The governance is problematic in the sense that it is a multilateral institution whose legitimacy is based on its member states - they have a lot of power and influence on the decision-making," said scholar Jennifer Prah Ruger, professor of health equity, economics and policy at the University of Pennsylvania. "It's in all of our interests to have an independent institution that tells the truth. We want that information for the common good."
The WHO denied it lacked authority or pulled its punches over countries' failings. "The conversations we have in private with member states can be very candid and frank," it told the Financial Times.
Another common complaint is that WHO procedures have become too ponderous. The body has an executive board of 34 member-state nominated representatives - but any other country may speak at its meetings. "In the end, it's a mini world health assembly," lamented one European official, referring to a protracted annual decision-making gathering of all 194 WHO member states. "So it's more inefficient again." The WHO disputed the notion it had become too unwieldy. It argued that the executive board was now "more participatory and more inclusive".
TOO CAUTIOUS, TOO SLOW?
Its approach to science - the foundation for any pandemic response - is a further source of contention. Critics charge that the WHO is slow to adapt its public health guidance to the latest research insights. They argue that it is sometimes too cautious when it lacks scientific evidence that meets the highest standards, even in cases where that is hard to obtain and where there are few if any health downsides to endorsing a course of action.
One oft-cited example is that it took until June 5 to issue a definitive recommendation that people should wear face masks. Questions have also been raised over its slowness to embrace the idea that the coronavirus can be transmitted via sprays of small particles known as aerosols that linger in the air for some time.
"My impression is that the WHO treats its scientific advice like some sort of academic research project," said Sir Venki Ramakrishnan, president of Britain's Royal Society. "They wait for definitive evidence to emerge before they issue guidance. The problem is that in a fast-changing scenario where urgent decisions have to be made, you have to go with the available evidence while you wait for the best evidence to accumulate."
The WHO said it was "cautious and rightly so" in its approach, as its technical guidance carried great weight. "We won't change or revise guidance on the basis of one or two studies," it said. "We do wait until we have a critical mass."
FUNDING PROBLEMS
The WHO's finances are a further perceived weakness. Many observers say its budget of US$5.84 billion (S$8.12 billion) for the two years 2020-21 is inadequate and rests on a precarious foundation - even though it has now been topped up to about US$7.2 billion with extra Covid-19 related contributions.
Member states account for barely half this total funding, with the WHO reliant for the rest on other sources, including philanthropic foundations such as Rotary International, non-governmental organisations and the private sector. The Bill & Melinda Gates Foundation was the second-largest contributor to the 2018-19 finances after the US.
The lack of reliable financing is amplified further because the majority of country contributions are voluntary rather than mandatory - meaning that just 13 per cent of the total current funding is expected to come from the compulsory member-state payments based on gross national income.
This dependence on nations' generosity yields wide donor disparities: In the last budget, Spain gave less than 10 per cent of Germany's contribution, while war-racked Libya pledged more than Romania and Croatia. A further constraint is that much of the voluntary funding is used for purposes dictated by the donors.
"Many countries have failed to fulfil their financial obligations to the WHO," said Dr Angus Dawson, professor of bioethics at the University of Sydney and a WHO adviser for more than a decade, including on the Covid-19 crisis. "That's why it has looked to the Gates Foundation and others to support its core activities. The ideal would be to have a global agreement about what the relevant budget would be - and then for nation states to actually pay the amount they've promised."
The WHO said it was trying to improve its funding model to make it more sustainable and predictable.
President Truman acclaimed the WHO as the natural evolution of public health efforts that had dispelled the "haunting fear" of cholera and plague epidemics. Mr Trump's withdrawal of the US' annual contribution of nearly US$450 million threatens to trigger a step backwards amid another pandemic.
"By all means criticise - but we must also fund and improve it," said Dr Howard Koh, professor of public health at Harvard University and assistant secretary of health in former president Barack Obama's US administration. "They are the only global health organisation we have. There really is no alternative."
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