FORT MYERS, Fla. - A new study led by an international group of scientists, including five from Florida Gulf Coast University, sheds light on how the Zika virus entered and circulated in Florida in 2016 and might do so again this year.
The Zika virus outbreak in Florida wasn't a single virus introduction but rather at least four separate introductions that each led to local chains of transmission, according to research conducted by the scientists, including co-leaders Drs. Sharon Isern and Scott Michael of FGCU.
The virologists' findings were published May 24 in the journal Nature (see full article here) just as mosquito season gets under way. Two other papers that further describe Zika transmission in the Americas, one of which is also co-authored by Isern and Michael, will be published in the same issue of the journal.
Isern and Michael are experts in virology, having studied Florida outbreaks of the related dengue virus in Key West in 2009-10 and Port St. Lucie in 2013.
"We realized that our longstanding collaborations with the Miami-Dade Mosquito Control District and the Tampa Department of Health Laboratory would provide critical samples to track and understand this major outbreak of Zika virus," Isern said.
They quickly reached out to other experts, including Dr. Kristian Andersen of the Scripps Research Institute in La Jolla, Calif., and Dr. Pardis Sabeti at Broad Institute in Cambridge, Mass.
"The expertise of Drs. Sabeti and Andersen in sequencing and genomic analysis were critical to this multi-group effort," Michael said.
Three recent FGCU graduates - Amanda Tan, Lauren Paul and Carolyn Barcellona - also took part and are authors on both papers.
Zika virus causes fevers, rash, headache, joint and muscle pain. It has also been linked to birth defects in some babies born to infected mothers, and can cause microcephaly, in which babies are born with underdeveloped heads and brain damage.
By studying the sequences of genomes - the complete blueprint of inheritable traits - from Zika viruses found in humans and mosquitoes, the researchers were able to show how individual viruses were related, similar to how DNA ancestry is used to discover family relationships in humans.
They discovered that instead of a single introduction sparking the outbreak in Florida, at least four distinct viral lineages became established and circulated in the state. Three spread through the Caribbean islands before reaching Florida while one spread through Central America, showing that Florida has been invaded multiple times and that more than one strain often circulated in a single area.
Florida is a likely location for Zika outbreaks, said Isern, because of the abundance of Aedes aegypti mosquitoes, which carry the virus, the climate and the fact that many people from the Miami area travel to countries in which the viruses are established.
The study's main findings include:
- At least four distinct Zika virus introductions contributed to the Florida outbreak.
- Local transmission in Florida likely started in spring 2016 well before the first local case was confirmed.
- Most Florida introductions are linked to the Caribbean.
Based on their findings, Isern and Michael believe that a similar transmission pattern is likely to emerge this year with multiple Zika virus lineages becoming established in the local mosquito population by infected people who have traveled in places where Zika is endemic. They expect to be able to determine where the viruses are originating and to compare the 2017 strains to those from 2016 to determine whether new introductions occurred or if those brought in during 2016 survived the winter and became established in Florida.
The research also indicated that mosquito control efforts in areas in which Zika virus was detected helped limit the spread of the disease. The scientists are hopeful that understanding what happened last year will help control efforts in 2017.
In addition to the FGCU scientists, the Florida study involved more than 60 researchers from 20 institutions, including the Scripps Research Institute, the Broad Institute of MIT and Harvard and the U.S. Army Medical Research Institute of Infectious Diseases, whose researchers were co-leaders with Isern and Michael; the University of Oxford, the Fred Hutchinson Cancer Research Center, and the Florida Department of Health, among others.
To see the other Nature articles, go to: "Zika virus evolution and spread in the Americas," and "Establishment and cryptic transmission of Zika virus in Brazil and the Americas."