Lawmakers return to Capitol Hill on Tuesday with two big items on the agenda before the election: keeping the government open and providing extra funding to combat the Zika virus. A shutdown is highly unlikely, but a showdown over Zika money could keep tensions running high in Washington and at the Atlanta-based Centers for Disease Control and Prevention.

In an interview Thursday with The Atlanta Journal-Constitution, the CDC’s director, Dr. Tom Frieden, said the federal agency, which is conducting much of the front-line work on Zika, is nearly out of money and that Congress must approve new funding as soon as possible.

“Basically, we’ve run out,” Frieden said of the $222 million previously allocated to fight the virus. “The sooner they act, the sooner we can make progress. Some of the studies that we have not been able to start are multiyear studies that require funding in the short term.”

Before lawmakers left for their seven-week summer recess, the two parties were deadlocked over Zika money. The Obama administration initially asked for $1.9 billion in emergency funding to fight the virus, but the $1.1 billion bill that emerged from the Republican-controlled Congress angered Democrats, who objected to a provision that would bar funding for Planned Parenthood clinics in Puerto Rico and proposed cuts to an Obamacare program in order to offset the costs of the Zika response.

Frieden said the urgency has only grown since lawmakers last considered the issue in July. There have been dozens of local mosquito-borne transmissions in Miami and 72 travel-related Zika cases confirmed in Georgia as of Sept. 1, according to the state’s Department of Public Health.

Frieden said the agency has been forced to siphon money from other programs aimed at Ebola, child immunization, HIV prevention and general emergency preparedness in states such as Georgia.

“The sooner we get additional dollars, the sooner we can make investments in the kind of programs that will protect Americans better,” he said.

Researchers are still searching for a cure and a treatment. The National Institutes of Health began vaccine trials last month, but it will be at least a couple of years before such a vaccine could become available.

Congress’ plans

It is still unclear how Congress will break the impasse over Zika.

Both parties agree that more money is needed, but Democrats are demanding that the GOP drop all contentious add-ons from the bill. Senate Democrats twice filibustered the GOP’s Zika measure this summer, and Majority Leader Mitch McConnell, R-Ky., has teed up another vote on the same plan for Tuesday.

The two sides will likely need to go back to the drawing board before the end of the month.

Georgia’s senior U.S. senator, Republican Johnny Isakson, said Congress needs to put partisanship aside and approve more Zika money, even if it is not offset with new spending cuts. (The latter is the preference of his Georgia GOP colleague, David Perdue.)

“If it’s $1.1 (billion) or $1.9 (billion), we know we’re going to spend whatever it takes to stop whatever we need to stop once it happens,” Isakson said in an interview last week. “Why not spend what it takes now to prevent it from happening at all?”

The issue has become a campaign issue for the incumbent, who’s seeking a third term in the Senate this fall. The campaign of his Democratic opponent, Jim Barksdale, slammed Isakson for leaving for recess earlier this summer without first addressing the issue.

“Before he left on his vacation, Senator Isakson refused to vote for funding to combat Zika unless it also cut funding for Planned Parenthood,” Barksdale campaign manager Dave Hoffman said.

Government funding

Lawmakers could choose to add the extra Zika money to the stopgap spending bill they must pass to keep the government open beyond Sept. 30 because they couldn’t agree on how to dole out federal funding between defense and domestic programs earlier in the year.

While shutdown showdowns — or the threat of them — have roiled Congress at several points in recent years, lawmakers are highly unlikely to allow that to happen this fall. That’s because virtually every member of the House and roughly one-third of the Senate is campaigning for re-election and will undoubtedly not want the threat of a shutdown hanging over their head.

There is some disagreement about whether Congress should tackle a final spending agreement in a lame-duck session after the election or leave all decisions for the new Congress and president in 2017.

Perdue said the duration of that stopgap matters less than beginning “an honest debate about the level of spending” and the federal debt.

“This is another year that has gone by where we have not addressed the total problem,” the junior senator said last week. Perdue is part of a group of lawmakers in the House and Senate pulling together a package of budget measures aimed at cutting down on the need for stopgaps.

Other legislation

For all the fiery rhetoric on the campaign trail, the Senate is unlikely to act on the other big piece of business waiting before it: the nomination of Merrick Garland for the vacant Supreme Court seat.

Republicans have held strong in their insistence that Congress wait until there’s a new president before considering a successor to the late Antonin Scalia. That hasn’t stopped some Republican senators from sticking to custom and meeting privately with Garland. Isakson and Perdue have not met with the nominee and have no plans to do so.

The impact of a split 4-4 high court is already being felt in Washington. Justices split evenly on whether to hear a North Carolina voting rights case last week, an outcome that prevented some of the law’s restrictions from being revived, as some had wanted.

The House also has plans to vote on a bill that serves as a direct response to the White House-sanctioned transfer of $400 million to Iran on the same day four U.S. prisoners were freed earlier this summer. Republican critics of the transaction say it was a ransom deal.

Otherwise, lawmakers could spend time in September considering the final version of this year’s defense policy bill.

Isakson is also seeking a vote in the Senate on his bill that would overhaul accountability programs at the Department of Veterans Affairs.

Isakson, the chairman of the Senate Veterans Affairs Committee, faced opposition earlier this summer from some Republican colleagues, including John McCain of Arizona, who voiced concerns about the bill’s options for veterans looking for health care outside the VA system and provisions related to firing problematic VA employees.

Isakson said he’s spoken with McCain and GOP leaders and is hoping to secure time for consideration on the Senate floor soon.