WASHINGTON, June 14 -- Donald Trump once promised to end HIV, at home and around the world. What he actually did was cut the programs that were ending it, and the United Nations has now put a number on the consequences. A new UNAIDS assessment finds that global HIV prevention has collapsed in the wake of the administration's aid cuts, with the use of preventive medication down sharply and an entire architecture of community-level services dismantled. The agency's projection is blunt: millions of new infections and deaths over the next four years that would not have happened otherwise. This is not an accounting dispute. It is a body count attached to a policy choice.

The headline figure is the one the administration will least want to dis...