Staff at the US Centers for Disease Control and Prevention have been ordered to stop communicating with the World Health Organization, according to a new memo, dealing a significant blow to global health efforts.

Federal health officials have been instructed to temporarily stop any “external communications” to the public, according to two officials with knowledge of the situation.

The Trump administration ordered an immediate pause on public communications from federal health agencies like the CDC, FDA, and NIH. The U.S. Department of Health and Human Services (HHS) says it expects the pause to be temporary.