A new study by a large group of international researchers led by scientists at The Scripps Research Institute (TSRI), US, has explained how Zika virus entered the US via Florida in 2016, and how it might re-enter the country this year. The research was published in Nature on 24 May.
The researchers created a family tree showing where cases originated and how quickly they spread. To do this, they sequenced the virus's genome at different points in the outbreak. The researchers found that transmission of Zika virus began in Florida at least four, and potentially up to 40, times last year. They also traced most of the Zika lineages back to strains of the virus in the Caribbean.
"Without these genomes, we wouldn't be able to reconstruct the history of how the virus moved around," said TSRI infectious disease researcher and senior author of the study Kristian Andersen. "Rapid viral genome sequencing during ongoing outbreaks is a new development that has only been made possible over the last couple of years."
The team found that several factors led to a ‘perfect storm’ for the spread of Zika virus in Miami, including Miami being home to year-round populations of Aedes aegypti mosquitoes, the main species that transmits Zika virus and the area being a significant travel hub that brought in more international air and sea traffic than any other city in the continental US in 2016. In addition, Miami is an especially popular destination for travellers who have visited Zika-afflicted areas.
The researchers found that travel from the Caribbean Islands may have significantly contributed to cases of Zika reaching the city
Andersen said that, based on data from the outbreak, he sees potential in stopping the virus through mosquito control efforts in both Florida and other infected countries, rather than, for example, through travel restrictions. "Given how many times the introductions happened, trying to restrict traffic or movement of people obviously isn't a solution. Focusing on disease prevention and mosquito control in endemic areas is likely to be a much more successful strategy," he said.