By MIKE STOBBE, Associated Press

NEW YORK (AP) — More than 460 laid-off employees at the nation’s top public health agency received notices Wednesday that they are being reinstated, according to a union representing the workers.

The U.S. Department of Health and Human Services confirmed reinstatement notices went out to the former Centers for Disease Control and Prevention employees, but provided few details.

About 2,400 CDC employees lost their jobs in a wave of cuts across federal health agencies in early April, according to a tally at the time.

Whole CDC programs were essentially shut down, including some focused on smoking, lead poisoning, gun violence, asthma and air quality, and workplace safety and health. The entire office that handles Freedom of Information Act requests was shuttered. Infectious disease programs took a hit, too, including programs that fight outbreaks in other countries, labs focused on HIV and hepatitis in the U.S., and staff trying to eliminate tuberculosis.

An estimated 200 of the reinstated workers are based in the CDC’s National Center for HIV, Viral Hepatitis, STD, and Tuberculosis Prevention, HHS officials confirmed. Staffers at a CDC lab that does testing for sexually transmitted diseases are being brought back, said one CDC employee who wasn’t authorized to discuss what happened and spoke to The Associated Press on condition of anonymity.

Also reinstated are an estimated 150 employees at the CDC’s National Center for Environmental Health, including people staffing a lab that works on lead poisoning, according to the union and employees.

Layoffs at federal agencies were challenged in lawsuits, with judges in some cases ordering federal agencies to halt terminations of employees.

Officials at HHS have never detailed how they made the layoff decisions in the first place. And they did not answer questions about why the notices went out, or how decisions were made about who to bring back.

HHS spokesperson Andrew Nixon said the agency was streamlining operations and that “the nation’s critical public health functions remain intact and effective.”

“The Trump Administration is committed to protecting essential services — whether it’s supporting coal miners and firefighters through NIOSH, safeguarding public health through lead prevention, or researching and tracking the most prevalent communicable diseases,” he said.

This is not the first time that employees at the Atlanta-based agency were told they were being terminated only to then be told to come back. After an earlier round of termination notices went out in February, about 180 CDC employees in March were told to come back.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.