A second suspected case of mosquito-borne Zika infection was reported in Broward County on Thursday, two days after the Florida Department of Health announced a similar case in Miami-Dade — making South Florida the potential epicenter for the nation’s first local outbreak of the infectious disease.
In response to the second case, Florida Surgeon General Celeste Philip requested that the federal Centers for Disease Control and Prevention send a medical epidemiologist to help with the investigation. The health department also urged residents in the affected Miami-Dade and Broward neighborhoods to cooperate with requests for blood and urine samples to help determine the number of people infected.
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The health department has not disclosed the locations in Miami-Dade and Broward under investigation. If confirmed, the cases would be the first documented Zika infections caused by mosquitoes in the continental United States.
To date, no mosquitoes captured in Miami-Dade have tested positive for the Zika virus, according to an official familiar with the health department’s investigation. Miami-Dade officials set up mosquito traps this week in the neighborhood where the infected person lives. The state health department reported a suspected local transmission of Zika virus in the area on Tuesday — four days after the case surfaced.
The trapped mosquitoes were sent to a lab at Florida Gulf Coast University in Fort Myers to be tested for Zika virus and results came back negative, according to the official, who spoke on condition of anonymity.
Florida’s Department of Health declined to verify the test results for mosquitoes trapped in the Miami-Dade area under investigation. Mara Gambineri, a spokesperson for the Florida health department, said the agency is still investigating and had no new information to report.
But the Associated Press later reported that Gambineri had sent an emailed statement that “sexual transmission related to travel has not been ruled out” in the Miami-Dade case, and that not all the blood and urine tests from the people around the infected patient have come back yet.
The department reported seven new Zika infections Thursday, including three pregnant women in undisclosed counties, three residents in Miami-Dade and one in Palm Beach — raising the statewide total to 334 people who have contracted the infectious disease this year.
None of Florida’s confirmed Zika infections, including 92 people in Miami-Dade, have involved bites from local mosquitoes, according to the health department. The state’s official count does not yet include the suspected mosquito-borne transmission in Miami-Dade.
State and local officials have been looking for Zika virus in local mosquitoes for months, placing traps near homes of people with infections confirmed by the health department. Those areas are targeted for inspection, surveillance and spraying.
But a local epidemiologist said more can be done to prevent an outbreak following a local transmission.
Aileen Marty, a physician and professor of infectious diseases with Florida International University’s Herbert Wertheim College of Medicine, said containment efforts may be more effective if a health agency also were to test for the virus among residents of the Miami-Dade neighborhood under investigation.
“You have to test people,” Marty said. “Testing the mosquitoes is one thing. Think about how many mosquitoes there are and what percentage gets tested.”
Zika can be difficult to diagnose in part because only one in five infected people show symptoms, which include fever, joint pain, rash and red eyes lasting seven to 10 days.
Marty said the Centers for Disease Control and Prevention could help lead testing of people who have contracted Zika but are asymptomatic. It is unclear, however, whether any health agency is testing area residents for the virus.
The Department of Health did not respond to questions about whether the agency is testing people who live in the Miami-Dade neighborhood under investigation but said that “it is standard” to conduct blood testing in an area of epidemiological investigation.
The CDC has published a 58-page plan that outlines how the agency will respond to local transmissions of Zika, including the deployment of a CDC Emergency Response Team (CERT) capable of providing a wide range of help, from epidemiological investigation to public outreach.
CDC officials did not immediately respond to questions about whether a CERT team has been deployed to Miami-Dade. The agency said this week that Florida and local officials are leading the investigation, and that the CDC has provided funding, including $2 million for Zika preparedness and another $5.6 million awarded this week.
President Obama and Florida Gov. Rick Scott spoke by phone Wednesday about Zika.
The CDC updated its weekly count of Zika cases nationwide on Thursday, reporting that 1,404 people in 46 states have contracted the disease. Only Alaska, Idaho, South Dakota and Wyoming have yet to report a Zika infection.
Nearly all the cases were acquired by people traveling outside the country to areas where Zika is spread by mosquitoes, according to the CDC, which said 15 cases were sexually transmitted and one was acquired through laboratory exposure.
Marty said that in order to prevent a larger outbreak in South Florida, health officials need to also test people who are at greatest risk of local transmission.
“It's exactly what they should be doing,” Marty said. “They’ve got the mosquito trapping end of it very well done. Plus, they’re spraying for mosquitoes. But as far as I know, they haven’t started this whole surveillance of people.”
Zika cases reported in Florida as of July 21
Number of Cases
Total cases not involving pregnant women
Cases involving pregnant women regardless of symptoms*
* Counties of pregnant women are not disclosed.
** Does not include suspected case of mosquito-borne transmission
Source: Florida Department of Health