WASHINGTON — The feud on Capitol Hill over responding to the rapidly spreading Zika virus would seem to be largely a fight over how much money is needed to fight the mosquito-borne scourge.
But lurking just beneath the surface are issues that have long stirred partisan mistrust, including Republicans’ fears about the use of taxpayer money for abortion and possible increased use of contraception, and Democratic worries about protecting the environment from potentially dangerous pesticides.
Public health officials warn that the virus will not stop to check party affiliation — the mosquitoes that carry it bite Republicans and Democrats alike.
“This is no way to fight an epidemic,” Dr. Thomas R. Frieden, the director of the Centers for Disease Control and Prevention, said in a telephone interview on Tuesday.
“Three months is an eternity for control of an outbreak,” he said, adding: “There is a narrow window of opportunity here and it’s closing. Every day that passes makes it harder to stop Zika.”
The ancillary political issues have added an extra layer of complication that could further delay a final agreement on legislation to provide emergency funds to fight the virus, which can cause severe birth defects in infants born to infected mothers.
The White House first requested $1.9 billion to fight Zika in February. But only last week, the Senate approved a measure that would provide $1.1 billion in emergency funds, and the House approved legislation that would reallocate $622 million from existing programs, including efforts to combat Ebola.
While the House and Senate proposals remain to be reconciled, a new front in the fight emerged Tuesday as the House approved a Republican bill that would strip away environmental regulations on an array of pesticides.
Obama administration officials have threatened to veto the bill, which they say is simply a repackaging of legislation first proposed in 2005 to make it seem related to the Zika virus.
“Rebranding legislation that removes important Clean Water Act protections for public health and water quality is not an appropriate avenue for addressing the serious threat to the nation that the Zika virus poses,” a White House statement said.
For their part, House Republicans have accused the administration of putting up political roadblocks.
“In the midst of a Zika threat, the federal government should not be making it harder for people to kill the mosquitoes that could carry it,” Speaker Paul D. Ryan’s office said in a statement. “This is serious stuff. We’re not talking about annoyances at your summer barbecue. Mosquitoes are the carriers of life-threatening exotic diseases, among which are the Zika and West Nile viruses.”
Senator John Cornyn of Texas, the No. 2 Senate Republican, had also proposed language easing the regulations on pesticides in an alternative measure on Zika funding, but that proposal was defeated.
“We had a provision in the Cornyn amendment that dealt with these regulatory restrictions on use of certain types of pesticides and programs that are used,” said Senator John Thune of South Dakota, who is also part of the Republican leadership.
“We just think we ought to provide some relief,” Mr. Thune said. “Right now more than ever, the key until we get a vaccine is to try and make sure that people don’t get infected, and the way to do that is to eradicate mosquitoes. I mean, that’s what carries the disease.”
Congressional Democrats and administration officials said that exceptions to the regulations already exist for emergency situations like fighting Zika, and they accused Republicans of trying to exploit fears about the virus to repeal regulations they have long opposed.
“Over the years, proponents of exempting pesticide spraying from the Clean Water Act have used the crisis of the day as the reason to support their legislation,” Representatives Peter A. DeFazio, Democrat of Oregon, and Grace F. Napolitano, Democrat of California, wrote in a letter urging colleagues to oppose the Republican bill.
“First, it was the threat of West Nile virus, then it was fire suppression in the West, then it was protecting the nation’s food supply and drought, and now, in 2016, the focus is on preventing Zika,” they wrote.
Environmental regulations are hardly the only partisan sidelight in the debate over how to respond to the Zika virus. Because the virus can cause severe birth defects in babies of infected mothers, Republicans have had concerns that taxpayer funds might somehow be used to help provide abortions.
As a precaution, Senate Republicans insisted on writing language into their measure on Zika financing that reiterated the Hyde Amendment — a provision named for the longtime Illinois congressman Henry Hyde that bans the use of government money for abortions.
That amendment would automatically apply because the Zika measure was attached to a regular appropriations bill, but Republicans said they wanted to be sure the language was included regardless of the legislative form used.
There has also been debate about whether the government should stress contraception or abstinence in public education campaigns about how the Zika virus can be transmitted even more readily by sexual intercourse than by mosquitoes. That question is of potentially heightened concern among conservative Christians not only in the United States, but also in Latin American countries where the virus is already prevalent.
Congressional Republicans have not openly criticized any emphasis on the effectiveness and importance of contraception. But unlike the Senate measure, the House bill does not include money for community health programs that might stress such prevention. Instead, the House bill directs its money to mosquito control and vaccine development.
Federal health officials have emphasized that they do not believe it is the government’s role to tell women if they should become pregnant, but have noted that even Pope Francis has said that it is acceptable to use contraception to prevent Zika’s spread.
Even some Republicans said they worried that these other issues were distractions from the urgent need to appropriate money and fight the Zika virus. And the closer the virus is to their states, the more urgent they sound.
“We can have those side debates if people want to have them, make their points on it,” said Senator Marco Rubio, Republican of Florida. “But this is a public health crisis and we have got to address it, or people are going to get really sick here.”