PARIS, France (AFP) — Hundreds of HIV doctors and researchers have called on the Trump administration to reverse its sweeping aid funding cuts, saying they are “doing catastrophic harm” to the global fight against AIDS.

The United States (US) has historically been the world’s largest donor of humanitarian assistance, but President Donald Trump has slashed international aid since returning to the White House less than two months ago.

The cuts have had a huge impact on global efforts to combat HIV, tuberculosis, malaria and other health scourges, putting millions of lives at risk, humanitarian organisations have warned.

An open letter to US Secretary of State Marco Rubio signed by hundreds of high-profile HIV doctors, researchers and public health experts called on the government to change course.

“Unless reversed, the dismantling of the US-supported AIDS response will cause the deaths of an estimated six million people in the next four years, decades of progress will be reversed, and the world will face growing HIV epidemics across the globe,” said the letter, dated Thursday.

On Monday, Rubio announced that 83 per cent of all contracts under the United States Agency for International Development (USAID) have been terminated.

This meant an anti-HIV initiative called President’s Emergency Plan for AIDS Relief (PEPFAR), which is one world’s most successful public health efforts and has saved an estimated 26 million lives over the two decades, has been “virtually eliminated”, the letter said.

The cuts also immediately halted medical trials across the world, “leaving study participants stranded,” the letter said.

Research institutions have been stripped of funding, staff and political independence, it added. The prestigious US university Johns Hopkins announced on Thursday it would lay off more than 2,000 employees because of the USAID cuts.

Even if US courts eventually find these decisions illegal, “the human suffering and loss of lives happening now cannot be reversed,” the letter said.

Among the signatories was French scientist Francoise Barre-Sinoussi, who won a 1983 medicine Nobel prize for her work identifying the HIV virus.

The US government has said the funding cuts were aimed at reducing spending, while Trump’s billionaire advisor Elon Musk has boasted of putting USAID “through the woodchipper”.

The letter was published as researchers gathered for the Conference on Retroviruses and Opportunistic Infections in San Francisco.

Protests were held across the US last week calling for people to “Stand Up for Science”.