With peak mosquito season here, fears of an outbreak of the mosquito-borne (and sexually transmitted) virus Zika in the United States are mounting.

Meanwhile, Congress has done nothing to prevent the situation from getting worse.

Lawmakers just went into a seven-week summer holiday without passing a $1.1 billion spending bill — first requested by President Obama back in February — that would have helped fund many prevention and preparedness measures.

Top health officials from the Centers for Disease Control and Prevention and the National Institutes of Health have been beating the drum for Congress to pass the bill to help the country prepare for Zika all year. But it came to naught Thursday when lawmakers left for vacation with no Zika deal.

What happened? Republican lawmakers added provisions to the bill — to reduce funding for Planned Parenthood and water down environmental controls on pesticide use — which the Democrats said they couldn’t sign off on.

To find out what the failure to secure more dollars to fight Zika means, I reached out to health officials in the federal government, as well as those working on the ground in the states likely to be hardest hit by the virus.

There are still no documented Zika cases originating in the continental US, but more than 1,300 travelers have brought Zika here from abroad. Meanwhile, nearly 3,000 people in US territories (mainly Puerto Rico) have acquired the virus locally.

Officials predict it’s only a matter of time before we see an outbreak here, particularly in the Gulf Coast states that are home to the Zika-carrying Aedes aegypti mosquito.

That means we’re also bound to see babies with microcephaly, the birth defect Zika causes, from cases originating here. By the CDC’s count, there have already been nine births involving Zika-related defects in the continental US, and there are more than 340 pregnant women with the virus.

"The risk of Zika transmission in the US will go up," said Ron Klain, the former "Ebola czar" who’s now general counsel at a venture capital firm, without additional federal funding. "Ultimately, that will translate into more babies with microcephaly here."

States have largely been left to deal with Zika by themselves — and the response is a patchwork

In April, the Obama administration repurposed $500 million from the Ebola response as a stopgap measure to pay for the Zika response. But federal health officials told Vox that money is running out.

And those dollars haven’t trickled down to the local level, where many health departments have been left to prepare for Zika outbreaks largely on their own.

That’s a problem because not all local health departments are well resourced to deal with the threat.

"Some counties have [enough funding]," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. "Others are already stretched beyond capacity."

One of the better-off counties is Harris, Texas. Umair Shah, the county’s public health and environmental services director, said he’s all but given up on federal support for now — and has been long preparing for an outbreak with his own budget by ramping up mosquito control and surveillance.

But Zika also requires its own awareness campaign since it’s still relatively unknown, and information about the virus is rapidly evolving. A new study out today demonstrated for the first time that women can spread Zika to men through sex — not just men to women or other men, as was previously believed. Educating the public on these matters is essential — and exactly the kind of program the federal government could have helped pay for.

"We could have used those dollars to get the message out," Shah said. That message especially needs to reach women who are pregnant — or couples thinking about getting pregnant — and who are at risk of birth complications and defects.

So Shah has had to do things like reassign one of his staff physicians to focus entirely on Zika.

So far, there are 20 confirmed cases of Zika (in travelers) in his county and likely several more undetected. Soon, he said, mosquitoes could pick up the virus from these folks, and spread it around to others — not to mention potential cases of sexual transmission.

Poorer counties, like Hidalgo, Texas, which borders Mexico, are the ones that really worry health experts. They’ve had to scramble much more in the Zika response.

"For us, our border is extremely fluid, both legally and illegally," said Eddie Olivarez, the chief administrative officer for Hidalgo County Health and Human Services. "There’s a lot of trafficking back and forth, as well as cargo ships and containers, so the possibility of Zika-infected mosquitoes or immigrants [entering] is there."

Olivarez emphasized that dealing with Zika is not that different from dealing with any of the other mosquito-borne illnesses they see every year. "But there’s a new emotional twist," he added, since the potential for much longer-term impacts is clear. "If you have a Zika baby born, it’s going to be on the front page, an emotional burden on the community."

Unlike wealthier areas, Hidalgo has no lab capacity to test for mosquito-borne viruses like Zika. Olivarez could use the extra funding to build up that lab or, at the very least, send mosquitoes to get tested at the state labs every week. "Believe it or not, it costs us hundreds of dollars a week in shipping costs," he said. "And that’s money that comes out of my general fund."

For now, he’s had to be creative and shuffle resources around. "If we have someone going out and doing STD [sexually transmitted disease] education, or immunization or nutrition education — every one of our employees, regardless of division, [now] has to talk about Zika," he said.

Congress’s inaction will delay Zika research and vaccine development

At the federal level, the absence of new cash will also have a direct effect on developing a vaccine against Zika, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Right now the federal government has several Zika vaccine candidates that are ready for Phase I safety testing in humans. As those trials begin, Fauci's agency needs to start setting up Phase II trials to test whether the vaccine works in areas that have active Zika transmission. To do that, "We have to start spending a lot of money around the end of August and September," Fauci said. "And that’s when the money I’ve now been using runs out."

"It’s profoundly disappointing"

But without the money, the vaccine trials will be delayed considerably, as will the chances of a vaccine hitting the market in time to prevent future outbreaks. Given that Zika is likely to be with us for at least a couple more years, this delay matters.

CDC Director Tom Frieden told Vox in an email that the failure to pass the Zika bill will also hinder the research into the disease and, potentially, the prevention of future infections through early detection and surveillance.

"We can't find where the mosquitoes are spreading in the US and control them before this epidemic spreads further into the US," he said.

Without the additional federal funds, the CDC will also be less able to protect pregnant women who get the virus, and their babies, he added.

The political conundrum of Zika

Microcephaly cases in the US — as we’ve seen in other countries with Zika — are "the nightmare scenario you want to avoid," said Hotez. And it’s a scenario we may not actually see here for months.

If mosquito transmission is beginning now, it’s going to be seven to nine months for affected babies to be born — long after Congress’s summer holiday.

"The horse has left the barn, and there’s nothing you can do at that point," Hotez added. "It’s profoundly disappointing."

That’s part of the challenge of galvanizing political support for Zika: It won’t affect the whole of the country equally, and as the LA Times points out, the threat to many people still seems abstract. But it is real, and it is underway.