Given the rapid spread of Zika throughout Latin America and the Caribbean earlier this year, it was only a matter of time before the virus showed up here. But until recently, virtually all U.S cases of Zika had involved people infected by mosquitoes while traveling in countries where the disease is epidemic or by having sex with partners who were bitten there. That changed when health officials reported more than a dozen new cases of Zika that appear to have been transmitted by mosquitoes in Florida. The epidemic has entered a worrisome new phase that ought to have Congress scrambling to stop Zika in its tracks. But instead lawmakers in Washington decided to go on vacation.

The Aedes aegypti mosquito that spreads the virus is common in the tropical countries where Zika is rampant. But it's also present across much of the southern U.S. as far north as Maryland. There's no cure for the illness, nor is there a vaccine yet that would prevent people from being infected by it. The only defense against the disease's spread is a well-coordinated mosquito control program aimed at killing the adult insects and their larvae to prevent them from transmitting the virus. But so far Congress has refused to fully fund such an effort, even though allowing the epidemic to spread out of control risks a public health crisis of massive proportions.

Although most cases of Zika are relatively mild — many infected people don't even realize they have the disease — the virus can have serious consequences for pregnant women and newborns. In Brazil and other countries, the virus has been linked to a sudden upsurge in cases of microcephaly, a devastating condition that causes babies to be born with abnormally small heads, deformed skulls and severe brain damage. The damage is irreversible and infants born with the illness will suffer its effects for the rest of their lives. Zika has also been linked to a temporary but debilitating form of paralysis in adults that can last for years.

There have been more than 1,600 confirmed Zika cases in the U.S., including 48 cases in Maryland. So far there's no evidence of local transmission of the illness in Maryland, but that could change quickly.

Officials think the epicenter of the locally transmitted cases of Zika in Florida was a 1-square-mile area in the Wynwood neighborhood of Miami known for trendy restaurants, bars and shops. That is where they have concentrated mosquito control efforts using insecticide sprays to kill adult mosquitoes and water treatments to kill larvae. They've asked people living and working in the area to remove standing water where mosquitoes can breed, and they have collected urine and blood samples to gauge how rapidly the virus spread. The Centers for Disease Control and Prevention issued a warning last week for people to stay away from the area, something it had never done before in the continental U.S. But officials still don't know whether they have stopped the virus' transmission there completely, or whether its spread may be continuing in other neighborhoods.

Given that the mosquito season in Maryland is likely to last for at least another couple of months, officials here can't afford to let down their guard. Health officials have already stepped up mosquito control programs in Baltimore City and elsewhere around the region, but if Florida's experience is any example, eradicating the insects is a costly, time-consuming process and it's not clear Maryland has the resources to respond on the scale the problem demands. States are going to need federal help to avert catastrophe, and the fact that lawmakers have chosen this moment to go on vacation only makes their abdication of their responsibilities all the more unconscionable.