The Department of Health and Human Services has abruptly canceled more than $12 billion in federal grants to states that were being used for tracking infectious diseases, mental health services, addiction treatment and other urgent health issues.

The cuts are likely to further hamstring state health departments, which are already underfunded and struggling with competing demands from chronic diseases, resurgent infections like syphilis and emerging threats like bird flu.

State health departments began receiving notices on Monday evening that the funds, which were allocated during the Covid-19 pandemic, were being terminated, effective immediately.

“No additional activities can be conducted, and no additional costs may be incurred, as it relates to these funds,” the notices said.

For some, the effect was immediate.

In Lubbock, Texas, public health officials have received orders to stop work supported by three grants that helped fund the response to the widening measles outbreak there, according to Katherine Wells, the city’s director of public health.

On Tuesday, some state health departments were preparing to lay off dozens of epidemiologists and data scientists. Others, including Texas, Maine and Rhode Island, were still scrambling to understand the impact of the cuts before taking any action.