It remains unclear how a government shutdown would affect the Centers for Medicare & Medicaid Services if Congress can’t agree on a bill to send the president by midnight.

But unless the Senate unites today behind a short-term spending deal — and convinces President Donald Trump to go along with it — the federal government looks set to furlough thousands of public health workers and stop some services and payments temporarily.

The risk of shutdown grew Thursday, even as House Republicans passed a short-term spending bill last night.

But the more narrowly divided Senate was struggling to find a way forward. Some senators discussed the possibility of passing a series of continuing resolutions to fund government operations for one or two days at a time as negotiations continue on politically explosive issues, according to the Washington Post.

In the meantime, observers are trying to pinpoint the extent of employee furloughs, service reductions and late payments that could be associated with a shutdown.

Rep. Bill Huizenga (R-MI) reported that CMS did not respond to a House committee request for guidance on ongoing benefits and payments. But he said officials did note that Medicare doesn’t pay in real time and that issues would likely only arise “if the government is shut down for more than two weeks.”

CMS also could hold claims, similar to their process with doctors in a previous situation, according to the Huizenga.

There might be an impact on “non-essential services” at CMS, but it would be up to the Department of Health and Human Services to decide the details, according to the Congressional Research Service.

At other agencies, planning documents and interviews with officials who survived the last federal shutdown in 2013 revealed some of the potential challenges ahead.

STAT News reported the Food and Drug Administration would likely forego updating mislabeled medications or conducting food safety inspections; the Centers for Disease Control and Prevention would furlough major staff in the middle of a severe flu season; and the National Institutes of Health might suspend clinical trial enrollment.

The shutdown “was this time in which that I felt I really couldn’t do my job, as CDC director, of keeping Americans safe, because more than 8,500 of my staffers had been told to go home, and they do important things that protect Americans,” former CDC head Tom Frieden, M.D., told STAT. “It’s unsafe, it’s terrible for government, it endangers Americans, and it doesn’t save any money. So it’s a really bad thing to have happen.”

Based on a 2017 contingency plan, STAT estimates HHS would furlough about 41,000 of its 82,000 workers, with some sub agencies retaining more essential staff than others.