Is Miami-Dade the No. 1 leader in breaking local Zika transmission?

Miami-Dade Mayor Carlos Gimenez said that in 2016 the county became a global leader in fighting the mosquito-borne Zika virus.

"We were the first community in the world -- let me repeat that -- the first community and I believe the only community in the world to break the cycle of local transmission of the Zika virus," Gimenez said during his State of the County speech Jan. 18.

However, Gimenez didn’t declare Zika dead forever -- he warned that the county must remain vigilant: "We may be in the off season, but that does not mean that our work is over."

Gimenez, a Republican re-elected to his last term in November, has a point about local transmission. The last of the four local transmission zones were cleared in Miami-Dade by mid December 2016. However, he omitted some caveats about Zika transmission and Miami-Dade’s special circumstances compared with the rest of the world.

Zika in Miami-Dade

Zika has been around for decades. But the current outbreak started in 2015, when Brazil reported cases of more babies being born with abnormally small heads, a condition called microcephaly. That condition was connected to mothers infected with Zika.

The Centers for Disease Control defines areas of active Zika virus transmission as having two or more locally acquired cases of Zika virus infection, within two weeks, within 1 square mile. Those cases must be in separate households, with travel and sex ruled out as potential causes.

Using those guidelines, the Florida Department of Health declared active Zika transmission zones and then lifted them when 45 days passed without any new local cases in those zones. 

In July, the first local Zika cases were reported in Miami-Dade County. Over the next few months, the state declared four local Zika transmission zones.

The state lifted the first zone, in Wynwood -- a trendy area near downtown Miami -- Sept. 19. That was the first community in the world to break local transmission, CDC spokesman Benjamin Haynes said.

The state lifted the last of the four zones, in part of South Beach, on Dec. 9. But officials didn’t declare Zika entirely kicked to the curb forever; Miami-Dade remained a "cautionary area" according to the CDC. Officials warned that isolated cases could continue to appear --  the most recent one was Dec. 15.

Let’s look at how Miami-Dade compared with some other areas in curbing Zika.

In addition to Miami-Dade, only one other area in the United States had local Zika cases: Brownsville, Texas. Miami-Dade reported 257 cases of local transmission, while Brownsville reported six. The Texas Department of Health never declared a local transmission zone in Brownsville, but the CDC called it a "cautionary area."

It’s difficult to compare Miami-Dade to other places where the Zika virus has been far more widespread. Brazil has had more than 128,000 cases and continues to battle Zika. Local transmission continues in Puerto Rico, which had more than 100 new cases this month and more than 37,000 since 2015. In Singapore, the government designated "Zika clusters" and announced that it had no more Dec. 15 after its last new case was reported Dec. 10.

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However, the "only place it really stopped is in Florida," said Daniel Epstein, a spokesman for the Pan American Health Organization.

There were other areas in the world where Zika dropped off before it hit Miami-Dade. For example, the outbreak in French Polynesia affected an estimated 28,000 people and lasted until 2014, said Monika Gehner, a WHO spokeswoman.

Some caveats

While Miami-Dade got kudos from the CDC for efforts to curb Zika, experts caution that it can return, particularly when the temperature rises.

It’s too early to claim elimination, said Duane J. Gubler, an emerging infectious disease expert at Duke-NUS Medical School in Singapore.

"The absence of reported cases for a few months does not confirm the transmission cycle is broken," she said. "After a year with active surveillance, I would probably accept it."

Florida also has certain advantages compared with other places of the world that have been struck by Zika, including better access to testing patients to verify that the virus is actually Zika.

Also, in South Florida, with air conditioning and screens and modest mosquito density levels, transmission is less likely than countries that have less of that protection, University of Florida biostatistics professor Ira Longini said.

"There is no cycle to break," he said. "Sustained transmission is impossible, but you do get small outbreaks when introductions occur."

Our ruling

Gimenez said Miami-Dade is "the first community in the world to break the cycle of local transmission of the Zika virus."

The CDC says that Wynwood, an area in Miami, was the first to break local transmission in September. The last of four local transmission zones was lifted Dec. 9.

There are some caveats about Gimenez’s claim, including that only one other county in the United States had local cases, and a far smaller number. Some other places took a far greater hit from Zika than Florida did.

Experts caution that Zika cases could return to South Florida, a point Gimenez also acknowledged in his speech.

We rate this claim Mostly True.