The day’s gathering, led by the Centers for Disease Control and Prevention, is intended to help state and local officials plan for worst-case scenarios.
There are 312 confirmed cases of Zika in the continental United States, including 27 pregnant women. All cases involve travelers who were infected abroad, except for six cases involving sexual transmission. In the U.S. territories, Puerto Rico has by far the most cases -- 325, including more than three dozen pregnant women.
But there are huge disparities in readiness on the front lines of mosquito control.
“It’s a patchwork,” said Lyle Petersen, who heads CDC’s vector-borne diseases division, showing a map of counties in the continental United States with vector-control programs in place as of March 1. Many of those programs are stand-alone operations, which makes data sharing and planning coordination with health departments more difficult.
Through part of the country's midsection, states like Nebraska and Missouri don’t appear to have anything in place. Even in states like Texas, which experts expect to be among the most likely locations for local transmission of Zika, vector-control programs are concentrated along the Gulf coast.
What’s more, states can't rely on the same mosquito-fighting strategies they've used to deal with problems like West Nile virus, Petersen said.
Controlling West Nile typically includes community spraying. But the Aedes aegypti mosquito, the primary transport for Zika, doesn’t venture very far. Its approximate flight range of about 150 yards means more targeted spraying around individual homes, Petersen said.
Officials' worries already have shifted their focus. In the Houston area, Umair Shah, executive director of the Harris County public health and environmental services department, said his staff is spending significant time on Zika instead of on other duties. Doing surveillance of the mosquitoes — and pregnant women, who are most at risk — is critical, he said.
“We can’t spray our way out of this situation,” Shah told the summit.
Many communities don't have the resources to do the labor-intensive work necessary to trap mosquitoes and test them to see whether they are infected with the virus. That leaves them with spraying, and that often ends up being done in response to complaints about nuisance mosquitoes instead of those carrying infectious diseases, he said.
Federal officials say the unprecedented kinds of health conditions linked to the pathogen greatly increase the urgency of action.
“We’ve never had a mosquito-borne pathogen that could result in a birth defect,” said CDC Director Thomas Frieden, referring to the broad range of birth abnormalities now linked to the virus, including microcephaly, vision and hearing loss and other developmental problems for a newborn. “The mosquito population can double in days and weeks. Can our response keep pace?”
The bottom line, he said, is that the United States needs sustained mosquito control throughout the entire country. No state has enough money or staff to do the advanced preparation that's necessary, Frieden said.
Officials referred to the lengthy delays by the World Health Organization and local governments in responding to the Ebola outbreak in West Africa in 2014.
“If we wait until the public is panicking because babies are being born with birth defects, we have waited too long,” said Amy Pope, deputy homeland security advisor in the Obama administration.
The Obama administration is seeking $1.9 billion in additional emergency funding to fight Zika at home and abroad, but Congress has so far refused to grant the request. Lawmakers instead have said the administration should use leftover funds from emergency Ebola funds.
Ed McCabe, chief medical officer for the March of Dimes, said there is a "very narrow window that will close rapidly" if officials don't act soon to save "dozens and possibly hundreds" of babies in the United States from potentially devastating birth defects and developmental problems.
Most of the evidence available now links the virus to the more visible types of severe fetal abnormalities. But damage from congenital viral infections is far-reaching and may not show up until years later, affecting learning in school, McCabe said.
It's impossible to prevent most birth defects, he noted. "But this is not the situation with this virus. We know what we have to do to protect pregnant women from being bitten by mosquitoes," he said.
The funding issue is hampering the speedy development of urgently needed diagnostics and other rapid-testing capabilities, officials said. Federal researchers are currently working with commercial companies to develop a test that will quickly determine whether a pregnant woman has contracted Zika.
"But it's like a little game of cat and mouse because the developers are reluctant to put a whole lot of skin in the game" until they know there is U.S. government money backing the projects, said Nicole Lurie, assistant secretary for preparedness and response at the Health and Human Services Department.