Geneva, Switzerland - The World Health Organization warned on Wednesday that US funding cuts would have "a devastating impact" on programs battling tuberculosis, endangering millions of lives.

Global efforts to battle TB – the world's deadliest infectious disease – have saved more than 79 million lives in the past two decades, averting around 3.65 million deaths last year alone, the United Nations health agency said.

But the "abrupt funding cuts" implemented to most US foreign aid spending since President Donald Trump returned to power in January "now threaten to undo these hard-won gains, putting millions – especially the most vulnerable – at grave risk," WHO warned.

Trump signed an executive order on his first day in office demanding a 90-day freeze on all US foreign aid, to give his administration time to review overseas spending.

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And he has essentially dismantled USAID, the primary organization for distributing US humanitarian aid.

WHO said Washington had been providing approximately a quarter of all international donor funding for TB – around $200 million to $250 million annually.

"These cuts put 18 of the highest-burden countries at risk, as they depended on 89% of the expected US funding for TB care," it said.

The UN health agency said the African region was hardest hit by the funding disruptions, followed by South-East Asia and the Western Pacific.

"Any disruption to TB services – whether financial, political, or operational – can have devastating and often fatal consequences for millions worldwide," Tereza Kasaeva, head of WHO's global TB program, said in the statement.

The impacts of the Covid-19 pandemic demonstrated that, she said, pointing to the more than 700,000 excess deaths from TB recorded between 2020 and 2023.

"Without immediate action, hard-won progress in the fight against TB is at risk," she said.

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Essential services and drug supply chains were breaking down due to staff suspensions, lack of funds, and data failures, it warned.

Laboratory services had also been "severely disrupted", it added, while "data and surveillance systems are collapsing", threatening TB screening and contact-tracing.

USAID, which had been the world's third-largest TB research funder, had meanwhile halted all its funded trials, "severely disrupting progress in TB research and innovation", WHO warned.

"Without immediate intervention, these systemic failures will cripple TB prevention and treatment efforts, reverse decades of progress, and endanger millions of lives."