14 Zika cases linked to Miami mosquitoes; CDC cites possible insecticide resistance

Florida Gov. Rick Scott has called on the Centers for Disease Control and Prevention to activate their Emergency Response Team (CERT), after the state’s health officials identified 10 additional cases of Zika virus infection that appear tied to local mosquitoes. That brings the total number of cases believed to be linked to local transmission up to 14. Later, the CDC director Tom Frieden said an eight-member CERT team is assembling by Tuesday in Miami-Dade County, where the local transmissions are occurring.

“Their team will consist of public health experts whose role is to augment our response efforts to confirmed local transmissions of the Zika virus,” Scott said. “While I encourage all residents and visitors to continue to use precaution by draining standing water and wearing bug spray, Florida remains safe and open for business.”

The new cases are concentrated within the same neighborhood in northern Miami-Dade County, where four initial cases of non-travel-related infections were reported last week. The 10 new cases were linked two people working at two places within a 150-meter area. Six of the cases exhibited no symptoms and were caught by surveillance screening. Health officials are creating a one-mile buffer zone around this area, where they will concentrate public outreach and mosquito control efforts.

More than 200 people in Miami-Dade and Broward counties have been tested for the virus; however, this area should not be considered a “ground zero” for the outbreak.

“It’s unlikely that we’ll ever know who brought it in and where they brought it in. It’s possible that there are occasional transmissions in local areas that are unapparent,” Frieden said. Echoing the CDC’s official guidance, Frieden recommended anyone traveling from a Zika-afflicted region to use mosquito repellent with DEET for three weeks to protect transmission into local communities.

“[Florida Department of Health] has been testing individuals in three locations in Miami-Dade and Broward Counties for possible local transmissions through mosquito bites,” Gov. Scott said in a statement. “Based on DOH’s investigations, two locations have been ruled out for possible local transmissions of the Zika virus. DOH believes local transmissions are still only occurring in the same square mile area of Miami.”

The CDC also issued a travel advisory for the affected area in northern Miami.

“We’re advising pregnant women not travel to this area that the Florida Department of Health has identified,” Denise J. Jamieson, co-leader of the pregnancy and birth defects team for the CDC’s Zika response. “In addition, we’re recommending that women who are considering pregnancy to not get pregnant for up to eight weeks after returning from that area.”

Men who have traveled in this area should wait at least six months before engaging in sexual intercourse with a partner who is pregnant or who might become pregnant. This travel guidance applies to anyone who visited the neighborhood on or after June 15, Frieden said, the earliest known date when people could have become infected based on information available today.

Gov. Scott and the Florida Health Department did not say whether officials had found mosquitoes in the area carrying the Zika virus, one of the standard methods of confirming local transmission. However, Frieden stated early attempts at mosquito control aren’t working as expected, potentially due to insecticide resistance or hard-to-reach breeding areas.

Health officials have administered two types of pyrethroids, chemicals that should kill young mosquitoes, to standing water in the neighborhood, but the insect’s larvae have persisted. A CDC expert will conduct tests over the next week to three weeks to determine if Miami’s mosquitoes are resistant to this first line of defense. If resistance is found, other mosquito control tools will be implemented, Frieden said, but the options are limited.

Gov. Scott and Frieden asked residents to remain vigilant and practice mosquito control methods to stem the possible spread of the disease, which can cause birth defects and brain inflammation. The CDC director said every precaution is important because researchers don’t know the long-term impacts of Zika, especially for microcephaly-free children born to infected mothers.

“These effects may only become apparent months or years in the future,” Frieden said, adding experts expect four symptomless infections for every person who shows signs of Zika.