This post has been updated.
On Thursday, Health and Human Services Secretary Sylvia M. Burwell, CDC Director Tom Frieden and Deputy Homeland Security Advisor Amy Pope hosted a videoconference with governors and local officials from the states with the highest risk for local transmission — Alabama, Arizona, Florida, Louisiana, Mississippi and Texas — along with officials from Georgia, Hawaii, California and Los Angeles County.
“We’re thinking through with them all the things that may happen when there is that first suspected case,” Frieden said in an interview afterward.
The response includes case monitoring to minimize the spread of infection, appropriate testing, prompt investigation and communication with the public, according to a summary of the plan.
U.S. officials are anticipating local cases of Zika infection because the mosquito that is the primary vector is found throughout the South as well as in parts of the Southwest and even Midwest. But they do not expect an explosion of cases, as has been seen in Puerto Rico and some countries in the Caribbean and South America.
Americans generally have more air conditioning and window screens and live in less densely crowded conditions than in those Zika-affected regions, Frieden noted. And the Aedes aegypti mosquito's range is only about a few blocks in its lifetime.
“We don’t think this is going to be a very common problem, but we do think it’s going to be a very high-profile problem,” Frieden said. Based on past experience with chikungunya and dengue, which are related viruses transmitted by the same type of mosquito, he said, communities are more likely to see a scattering of single cases, not clusters of them or widespread outbreaks.
But managing expectations around those single cases actually may trigger more anxiety because it may take 10 days to determine their origin. “It’s not always the easiest of dynamics,” Frieden said.
Among the issues raised by the governors was the adequacy of mosquito-control programs, which are locally funded, and the capacity of state labs to do Zika testing, he said.
“One of the things they’re concerned about, if they had local transmission, is they might have huge demand for testing that isn’t really clinically indicated,” Frieden said. “That could overwhelm lab capacity."
Nearly 700 people in the continental United States have been infected with the virus. Except for about 10 cases spread through sexual transmission, all have been travel-related cases. Florida has the largest number, with 132 cases.
In a statement released after the call, Florida Gov. Rick Scott said he requested that the CDC provide additional Zika tests to Florida to allow individuals, especially pregnant women and new mothers, to see if they have ever had the Zika virus. Scott said he also asked for additional resources to hire personnel and increase training for mosquito surveillance and control.
Despite dire warnings from public health officials and experts about the spread of the virus this summer, Congress has balked on approving the Obama administration’s $1.9 billion request for Zika funding. The Senate approved $1.1 billion in funding in May. The House passed legislation that would provide $622 million, which would be drawn from money already set aside for Ebola programs.
In April, the administration redirected more than $500 million from Ebola funds to get geared up for Zika, but Frieden and other experts say Congress needs to act immediately so expanded measures can be put into place and be most effective when cases surface.
The administration also redirected about $44 million in general emergency-preparedness grants that state and local public health departments expected to receive starting in July.
Administration officials say Congress needs to replenish both the Ebola and emergency-preparedness funding. Otherwise, Frieden has said, the government will have fewer resources for critical studies of what happens to Zika-infected mothers and their children or for research on new mosquito-control technologies.
Federal health officials say the first priority is to protect pregnant women and their developing babies. They recommend that any woman who has had possible exposure to Zika be closely monitored and tested during her pregnancy. But that goal may not be met: Only 20 percent of people who are infected even show symptoms.
Zika usually remains in the blood of an infected person for about a week; after that, making a diagnosis can be more difficult. Other tests can look for the presence of antibodies that humans produce in response to the virus. But people who have been previously infected with dengue or other viruses related to Zika also produce antibodies. Tests to differentiate between those antibodies take longer and are more complicated.
Another major challenge could be identifying the location of transmission. Frieden said health officials would probably draw a map around an area and provide public advisories about traveling there.
“No one wants to be that place,” he said. “But if you had a cluster, then the public has a right to know about ongoing transmission.” Pregnant women may want to consider avoiding the area, he said.
In places in Latin America where Zika has spread widely, about 2 percent of the adult population is getting infected every month. That may be even higher during peak months, he said.