NEW YORK CITY, New York: Hundreds of employees at the U.S. Centers for Disease Control and Prevention (CDC) are being permanently laid off this week, with at least 600 receiving final termination notices following a recent court decision that shielded some divisions but not others, the workers' union said.

The American Federation of Government Employees (AFGE), which represents more than 2,000 CDC staff, said the full scope of the cuts remains unclear because the U.S. Department of Health and Human Services (HHS) has not disclosed details. "Due to a staggering lack of transparency from HHS, the union hasn't received formal notices of who is being laid off," AFGE said in a statement.

HHS referred reporters to a March statement saying the restructuring is intended to make federal health agencies more efficient and responsive.

The layoffs include about 100 employees from the CDC's violence prevention programs, a move some staff described as especially painful just weeks after a gunman fired more than 180 rounds into the CDC's campus, killing a police officer. "The irony is devastating," some affected employees wrote in a blog post. "The very experts trained to understand, interrupt, and prevent this kind of violence were among those whose jobs were eliminated."

The cuts follow an April 1 announcement by HHS that thousands of CDC and other health agency employees would be laid off as part of a sweeping downsizing. Many have been on administrative leave since then, paid but barred from working, while lawsuits challenged the move.

Last week, a federal judge in Rhode Island issued a preliminary ruling protecting some CDC divisions, including those focused on smoking, reproductive health, environmental health, occupational safety, birth defects, and sexually transmitted diseases. However, staff in other offices, such as those involved in violence prevention and freedom of information, were not covered and are now losing their jobs.

Among the programs hit are efforts to prevent rape, child abuse, and teen dating violence, as well as international projects that helped countries track violence against children and set reduction goals.

"There are nationally and internationally recognized experts that will be impossible to replace," said Tom Simon, the retired senior director for scientific programs at the CDC's Division of Violence Prevention.