WASHINGTON — Congress abandoned the Capitol on 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-Wisconsin, told reporters Thursday.

But with Democrats hammering Republicans over neglect on a virus that attacks pregnant women, some Republican 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 (Florida), the onetime 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. Last week, U.S. officials announced 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 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.

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-Nevada, said during a floor speech.

But an influential bloc of conservatives remains 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-Alabama, 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 that they are hesitant to release money to his administration.

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