San Diego County Vector Control personnel prepare to spray for possible Zika-carrying mosquitoes in 2016. File photo courtesy County News Center

Just when international fears over the Zika virus began to fade in 2017, an undetected outbreak was peaking in Cuba just 300 miles off the coast of Miami.

A team of scientists at Scripps Research in La Jolla uncovered the hidden outbreak by overlaying air-travel patterns with genomic sequencing of virus samples from infected travelers.

The discovery is featured on the cover of the Aug. 22 issue of Cell, one of the most most respected scientific journals.

“Infectious diseases such as Zika are global problems, not local problems, and greater international collaboration and coordination is critical if we are to stay ahead of looming threats,” says Kristian Andersen, associate professor at Scripps Research and director of Infectious Disease Genomics.

“Through this study, we developed a framework for a more global, more proactive way of understanding how viruses are spreading,” he said. “The traditional reliance on local testing may not always be sufficient on its own.”

When the mosquito-borne Zika virus was discovered in Brazil during spring of 2015, it had already been circulating for at least a year, making its way to more than 40 countries. Very quickly, Zika ascended from a little-known virus to a source of international panic because it could cause microcephaly in babies born to women who contracted Zika during pregnancy.

Coordinated response to Zika relied upon countries accurately detecting cases and reporting them to international health agencies. By the end of 2016, data from these health agencies suggested that the epidemic was nearing its end.

However, Andersen and his collaborators found that an undetected outbreak was reaching its peak in Cuba at that time, off the radar of international health agencies. Surprisingly, the outbreak lagged other Caribbean countries by a year, likely due to an aggressive mosquito-control campaign that delayed the disease’s emergence, according to the study.

Andersen’s team notes that it’s still unclear today whether Zika transmission is ongoing, as discrepancies in local reporting continue to hinder detection. While using travelers as sentinels can shed light on outbreaks, as it did in this case, richer public data is necessary to get ahead of threats, Andersen said.

Public health organizations and academic labs must step up their information-sharing practices, he said. That, along with better detection technologies and improved government funding for activities such as mosquito surveillance, could help avert future outbreaks.

Chris Jennewein

Chris Jennewein is Editor & Publisher of Times of San Diego.