WASHINGTON — The federal government, preparing for homegrown cases of the Zika virus, is planning to release a proposal for responding to them, health officials said Friday.
The 60-page document, a blueprint for action when the first cases of locally transmitted Zika occur in the continental United States, could be released early next week, officials at the Centers for Disease Control and Prevention said. They emphasized that it was a working draft that could change based on advice from state officials.
Sylvia Mathews Burwell, the secretary of health and human services, and Dr. Thomas R. Frieden, the director of the CDC, spoke by videoconference with state governors Thursday about the plan. On Friday, experts with the CDC talked with state health departments.
"We know that Zika is a completely unprecedented problem and the front-line response is going to be crucial," Dr. Anne Schuchat, the CDC's deputy director, said in an interview. "The summer is starting, and the mosquitoes are coming."
The Zika virus is transmitted by the Aedes aegypti mosquito — a bug that in the United States is found mostly in the South and Southwest, though its range can spread in the summer. No one has been infected with Zika by a mosquito in the continental United States, but health experts expect it to happen.
The health experts do not expect an explosive Zika virus transmission like the recent one in Brazil because many homes in the United States are air-conditioned and keep their windows closed. Many also have screened windows that keep mosquitoes out. The United States is much less densely populated than the areas of Brazil where the Zika outbreak occurred, a hindrance to transmission given that the Aedes aegypti mosquito rarely flies more than a block in its lifetime.
Many health experts worry, however, that a Zika outbreak could be difficult to fight because 80 percent of the people infected with it experience no symptoms.
"If we have a homegrown case, that's a game changer," Dr. Thomas E. Dobbs III, Mississippi's epidemiologist, said in a telephone interview.
Zika causes debilitating birth defects, including abnormally small heads and damaged brains from a condition called microcephaly. Health officials are focusing on protecting pregnant women from exposure to mosquitoes or people infected with the Zika virus. The disease can be sexually transmitted, too.
At the heart of the plan are the CDC's multidisciplinary rapid-response teams. They will provide state and local governments with technical and logistical expertise, epidemiology, laboratory services and advice on fighting mosquitoes. The CDC has used rapid-response teams for years to track many diseases.
"We know that this is a critical time," Schuchat said. "It's really the time to get ready."
If the disease spreads like its cousins — dengue and chikungunya — experts say they expect there to be individual cases that are essentially one-offs, not large clusters that spread.
Still, Schuchat cautioned that health officials were not going to assume that Zika would behave that way.
"The first case is an important event," she said. She added that it might not be immediately clear whether the case came from a local mosquito until there were several, and that doctors, hospitals and local health authorities needed to be particularly vigilant.
"That first local transmission case is not going to come with a sign saying, 'I'm the first local transmission case,'" Schuchat said.
Many states have already been preparing. In Mississippi, health experts have been gathering mosquito samples in five places in every county since May, Dobbs said, but no Aedes aegypti mosquitoes have turned up.
"This has really jarred people out of any type of complacency they had," said Joseph M. Conlon, a retired Navy entomologist who is a technical adviser to the American Mosquito Control Association. "They've gotten into planning mode big time."
In states like Mississippi, where poverty and modest tax bases make mosquito control spotty, contracts with private vector-control companies are being put in place. Such companies are commonly used in states plagued by hurricanes, Conlon said.
The CDC is "helping to fill the gaps," Schuchat said. "But the states need to own the issue, and we think they really are stepping up towards that."