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 told federal public health agencies like the CDC that they are not to communicate health messages for now. The hold includes memos, reports, online posts, website updates and other forms of communication. Scientific meetings were also canceled for the time being, including of advisory panels.