Sen. Marco Rubio (R-Fla.) is ugring his Republican colleagues to act quickly on a funding request officials say is needed to combat the Zika virus. (Andrew Harrer/Bloomberg)

Congress abandoned the Capitol Thursday for an almost two-week break without addressing how to combat Zika, even as public health officials issue dire warnings about the spread of the mosquito-driven virus with summer approaching.

Republican leaders insist that a deal can be struck soon to provide the money federal health officials say is needed to develop a vaccine. They also played down the risk of waiting a little longer, arguing existing money is available for the initial steps needed to help contain the virus while lawmakers resolve the larger funding fight.

“They can get to work on this problem, and there’s money in the pipeline that’s already going out the door right now,” House Speaker Paul D. Ryan (R-Wis.) told reporters Thursday.

But with Democrats hammering Republicans over neglect on a virus that attacks pregnant women, some GOP lawmakers, particularly those in Florida and other warm-weather locales, expressed increasing anxiety about the slowly developing response as the warm weather breeds more mosquitoes.

“The CDC is saying we’re less than a month away from a mosquito [epidemic] in the U.S. I mean, I take that seriously,” Sen. Marco Rubio (Fla.), the onetime GOP presidential contender, said this week. “These are not politicians. These are scientists and doctors that are looking at this issue and telling us, you’ve got a real problem on your hands.”

For months officials at the Center for Disease Control and Prevention have been monitoring the outbreak of Zika in South America, particularly in Brazil, where hundreds of thousands of visitors will descend in August for the Summer Olympics and then return to their native countries. Last week, U.S. officials announced that they are monitoring hundreds of pregnant women for Zika signs and that there are growing concerns about a large outbreak in Puerto Rico.

In response to the Obama administration’s $1.9 billion Zika request, the Senate approved $1.1 billion in funding earlier this month while the House has passed legislation that would provide $622 million, which would be drawn from money already set aside for Ebola programs.

In April, the administration redirected an initial flow of more than $500 million from Ebola funds to begin the battle against Zika as it pressed Congress to act quickly on President Obama’s larger funding request. Democrats do not approve of pulling more money from the leftover Ebola account, because the initial plan two years ago called for any remaining funds to be spent helping nations overseas prepare to fight the deadly disease in the future.

Everything you ever wanted to know about the Zika virus and its spread across North and South America. (Daron Taylor,Claritza Jimenez/The Washington Post)

In public briefings and private meetings with lawmakers health officials have cited evidence linking Zika to a rare condition causing children to be born with abnormally small heads and underdeveloped brains. Hundreds of babies in Brazil have suffered this condition, and the outbreak that has spread to three dozen countries, primarily in the Americas.

[Zika outbreak: ‘The more we learn, the worse things seem to get’]

Instead of racing to fund efforts to thwart a potential health crisis, lawmakers are treating the Zika debate like regular legislation, approving Thursday the establishment of a House-Senate committee to hammer out differences in their competing bills.

Democrats have criticized the Republicans for weeks on the slow response, culminating with a media showcase Thursday on the House steps demanding that the traditional Memorial Day recess be eliminated so lawmakers could finish the issue next week.

“Republicans are going to do it again: take a week off and not going to worry about those pesky mosquitoes,” Senate Minority Leader Harry M. Reid (D-Nev.) said during a floor speech.

But an influential bloc of conservatives remain committed to reining in government spending, demanding cuts from other portions of the budget before allowing increased funds to battle Zika. Sen. Jeff Sessions (R-Ala.), a fiscal hawk, called it “weak” policy to just push $1 billion more into the effort without any assurance of the outcome, without some corresponding cuts to other federal programs.

“The big disagreement that we have and the difficulty we deal with is,” Sessions said, “should every time a billion-dollar or $2 billion project comes along, do we just borrow the money?”

Some Republicans also harbor such distrust of Obama — from executive actions on immigration, transgender issues in schools, overtime rules and other issues — that they are hesitant to release money to his administration.

These conservatives have reservations about how the government spent funds two years ago battling the Ebola outbreak, which was largely considered a success because of its very limited impact in the United States.

Rep. Mark Meadows (R-N.C.), a leader of the hard-line conservative House Freedom Caucus, called the Ebola response “certainly a success” but said that much of the roughly $2.7 billion in those funds was not spent in the most “prudent and logical manner.”

That has led conservatives to issue many more questions about how administration officials intend to spend any Zika money.

“Not having a real plan, where that’s spent and how it’s spent, is troubling and something that has to be addressed,” Meadows said.

[Congress struggles to strike deal on Zika funds as concern about the virus grows]

Others said there is just not the same level of immediacy and understanding of this virus as there was of Ebola, where thousands of Africans were dying within weeks of contracting it, and Zika moves more slowly and federal officials also have yet to formally announce a single domestic case.

Rep. Tom Rooney (R-Fla.) cited another, more basic rationale for his inability to win over more support from his colleagues: Washington’s unusually cold, wet spring.

“That actually may have played a role in it,” said Rooney, who supports higher funding levels but suggested the weather pushed mosquitoes to the back of lawmakers’ minds.

“Now it’s hot here,” Rooney said Wednesday outside the Capitol as the temperature crested 80 degrees, hoping his colleagues would now see the light.

Ryan and his closest allies have grown angry at the Democratic allegations that they are neglecting the issue. “To say that we are not sympathetic, understanding and balanced on the Zika issue would be wrong,” said Rep. Pete Sessions (R-Tex.), chairman of the Rules Committee.

Still, some Republicans fear the worst outcome, both in terms of public health and what it could mean for them politically.

“Obviously in South Florida where I’m from the problem is going to intensify,” Rooney said. “Hopefully not to the point where it’s some kind of an epidemic that if we don’t get something done we are culpable for not acting on this.”

Kelsey Snell and Catherine Ho contributed to this report.