The U.S. provides nearly half of the aid for global health, including childhood vaccination, H.I.V. treatment and disease surveillance.
The election of Donald J. Trump, with his mistrust of international institutions and his history of proposing deep cuts to foreign aid, has complicated a perilous landscape for global health organizations that were already in a frantic competition for sharply reduced funds.
Organizations that support the cornerstone health programs to vaccinate children, treat people with H.I.V. and stop the next pandemic through disease surveillance, among other goals, are seeking billions of dollars from high-income countries.
Their demands for support reflect mounting health challenges: Rates of infection with dengue fever are exploding in Latin America. The mutated mpox virus is increasingly transmissible between people, and there are fears that H5N1, avian influenza, is also evolving to spread between humans. Deaths from cholera, an ancient scourge, and measles are rising. The parasite that causes malaria is increasingly resistant to the drugs to treat it, and an invasive malarial mosquito is threatening African cities.
The organizations seeking financial commitments and the countries that fund them have helped save millions of lives in developing countries. The global rate of child mortality has dropped by more than half in the two decades since 2000. Malaria infections plummeted as bed nets and better drugs were distributed. H.I.V. went from being the top global killer to, in many places, a well-managed chronic illness.
The reality that these organizations are unlikely to get anywhere near the amount of money they are seeking is driving debate about whether — and how — the current global health system should be restructured.
Global health priorities are now competing with climate change and wars for funding, and aid budgets have already been cut in major donor countries, including Britain, Germany and Japan. Health organizations are bracing for the likelihood that the second Trump administration will sharply reduce contributions from the United States, as well.