The U.S. government’s efforts to battle an especially virulent flu season could be forced to pause if lawmakers fail to reach agreement on spending legislation before an early Saturday deadline.

The Department of Health and Human Services said on Friday that it would furlough half of its workers and suspend the Centers for Disease Control and Prevention’s influenza program, among other measures, if temporary funding for the federal government expires at midnight.

The CDC has reported widespread flu in the U.S., with millions of Americans having fallen ill this season, and more strains are emerging. The agency expects there could be an additional 11 weeks to 13 weeks of flu circulating in the country.

With the likelihood of a last-minute spending agreement in Congress in increasing doubt, the department, which employs nearly 81,000 people, posted guidance describing how its operations would be affected.

HHS would retain most of its staff “with a substantial direct service component,” according to the posting, keeping workers in units like the Indian Health Service. Other divisions would continue to support children and provide patient care for National Institutes of Health Clinical Center patients.

The Centers for Medicare and Medicaid Services would continue key activities related to the Affordable Care Act’s exchanges, including open-enrollment eligibility verification. Medicare would continue largely without disruptions, according to the HHS posting. Staff that make payments to states eligible for the Children’s Health Insurance Program also would continue to work, the posting said.

Among other operations that would close, the Food and Drug Administration could not support the majority of its food-safety activities.