Layoffs of 10,000 Health and Human Services employees begin. Agencies devoted to seniors, minorities and HIV prevention closed.

Employees across the massive U.S. Health and Human Services Department received notices Tuesday that their jobs were being eliminated, part of a sweeping overhaul designed to vastly shrink the agencies responsible for protecting and promoting Americans’ health.

On health economist Jay Bhattacharya ’s first day as head of the US National Institutes of Health (NIH), the chiefs of four of the 27 institutes and centres that make up his agency — including the country’s top infectious-diseases official — were removed from their posts. The unprecedented move comes amid massive cuts to research at the NIH.