LONDON (AP) — For the first time in the global AIDS epidemic that has spanned four decades and killed 35 million people, more than half of all those infected with HIV are on drugs to treat the virus, the United Nations said in a report released Thursday.

AIDS deaths are also now close to half of what they were in 2005, according to the U.N. AIDS agency, although those figures are based on estimates and not actual counts from countries.

Experts applauded the progress, but questioned if the billions spent in the past two decades should have brought more impressive results. The U.N. report was re...