Dangerous pathogens left unsecured at labs across Africa. Halted inspections for mpox, Ebola and other infections at airports and other checkpoints. Millions of unscreened animals shipped across borders.

The Trump administration’s pause on foreign aid has hobbled programs that prevent and snuff out outbreaks around the world, scientists say, leaving people everywhere more vulnerable to threatening viruses and bacteria.

That includes Americans. Outbreaks that begin overseas can travel quickly: The coronavirus may have first appeared in China, for example, but it soon appeared everywhere, including the United States. When polio or dengue appears in this country, cases are usually linked to international travel.

“It’s actually in the interest of American people to keep diseases down,” said Dr. Githinji Gitahi, who heads Amref Health Africa, a large nonprofit that relies on the United States for about 25 percent of its funding.

“Diseases make their way to the U.S. even when we have our best people on it, and now we are not putting our best people on it,” he added.

In interviews, more than 30 current and former officials of the United States Agency for International Development, members of health organizations and experts in infectious diseases described a world made more perilous than it was just a few weeks ago.