Without funding, the federal fight against the spread of the Zika virus will eventually come to a complete stop, officials say.
"It's very frustrating," said Dr. Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, part of the National Institute of Health.
"Very frustrating when you're trying address an emergency public health issue and the Congress doesn't act to give you the resources you need."
The Senate voted down to provide additional funding to the Centre for Disease Control and the National Institute of Health on Tuesday. The funding for combatting the disease has become bogged down in political mire as Congress looks to pass a bill to fund the government through Oct. 1.
For months, the federal agencies fighting the spread of Zika had to pull funds from accounts used to fight other diseases. First, it was from money meant to combat Ebola, and later from other more common ailments, such as heart disease, diabetes and cancer.
"When this activity began, there was no money that was allocated by Congress, so we needed to start our own activities," said Fauci. "We soon ran out of that money."
"As we approach the end of the fiscal year, unless we get an appropriation from Congress, both the CDC and the NIH will have to dramatically slow down and likely stop the Zika activities that we're already doing."
The CDC and the NIH have started safety trials of a possible vaccine for Zika, but can't move to severely affected areas in the country, like Florida and Puerto Rico, to begin efficacy trials.
So far, there are at least 55 reported cases of Zika in Florida that are believed to be locally transmitted, but about 2,700 reported travel-related cases in the U.S. Fauci said the number of infected individuals could be even higher as people with Zika typically don't show any major symptoms.
President Obama called on Congress in February to allocate $1.9 billion for Zika funding, a call they have not answered.
According to the CDC, Zika is typically transmitted through the bite of a mosquito. However, it can also be spread through sex if a person's partner is infected.
While infection is not considered to be life threatening, it has been found to have severe negative effects on pregnancy. Babies with Zika may be born with microcephaly, where the head is too small for the brain to properly develop, leading to other brain defects.
As to how effective the possible vaccine will be at this point, Dr. Fauci said it's too early to say.
"It's almost impossible to determine. It's very unlikely we'll get a diffuse, homogenous outbreak throughout the continental United States similar to that of Brazil or Puerto Rico."
Fauci said that with government resources, the CDC and the NIH would be able to start efficacy trials of a ZIka vaccine by the beginning of next year.