In the wake of the Obama administration’s warnings that funding to fight the Zika virus is quickly depleting, GOP Sens. Chuck Grassley of Iowa and James Lankford of Oklahoma questioned why billions in unappropriated Heath and Human Services (HHS) funds have not been used towards the cause.

In a letter written to HHS Secretary Sylvia Mathews Burwell Friday and released to the press Monday, the lawmakers asked why the administration has also been slow on distributing the $589 million to fight Zika — $510 million of which was originally intended for Ebola and was approved to be repurposed to fight the mosquito-borne virus.

According to the senators, as of July, just $112 million of the $589 million has been distributed despite the increase in cases seen in the United States.

Grassley and Lankford noted the secretary of State has the power to “reprogram any current fiscal year bilateral economic aide” to respond to the crisis.

“According to a Fiscal Year (FY) 2017 report from the Office of Management and Budget, at the beginning of FY16, the Department of Health and Human Services (HHS) retained $25.426 billion in unobligated balances; HHS is expected to have $20.996 billion at the end of FY16,” they wrote. “We urge you to act and use funding available to ensure our nation is prepared.”

The Centers for Disease Control and Prevention reports, as of August 24, there have been 2,517 confirmed cases of Zika in the U.S., 29 of them through mosquitos.

Zika funding is expected to be one of Congress’ top priorities when it returns from its August recess after two bills failed in the Senate earlier in the year. Democrats blocked the bills because money was not allotted to Planned Parenthood.

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