Immunity slows Zika’s spread in Florida

MIAMI — The waning of Zika outbreaks in the Caribbean and South America has helped slow the spread of the mosquito-borne virus in Florida this year, according to health officials.

Herd immunity, when enough people in an area are infected with a virus and develop resistance to it, likely has contributed to Zika’s decline outside the continental United States, Dr. Henry Walke, the U.S. Centers for Disease Control and Prevention’s incident manager for Zika response, was quoted as saying in the Miami Herald.

“People that were infected before can’t be infected again. That’s our understanding,” Walke said. “So you don’t have as much of the virus circulating. That’s true not only in Puerto Rico but throughout the Caribbean and throughout South America.”

However, experts warn that herd immunity elsewhere won’t stop the virus from re-emerging in the U.S. That has happened in Florida with other mosquito-borne viruses in recent years.

By the end of 2016, state health officials had confirmed 1,456 Zika infections in Florida, including 285 cases spread by mosquitoes in Miami and Miami Beach. The infections caused the CDC to issue an unprecedented domestic travel advisory warning pregnant women to avoid Miami-Dade County because the virus can cause severe birth defects.

There is no vaccine or treatment for the virus, which can also spread through sexual contact.