Until now, the Pan American Health Organization had no record of any Zika infection in Cuba in 2017, much less an outbreak. Following inquiries by The New York Times about the new study, published in the journal Cell, officials acknowledged that they had failed to tally 1,384 cases reported by Cuban officials that year.
That figure is a sharp increase over the 187 cases confirmed in 2016 and is “in line with the estimates for 2017 from our own study,” said Kristian Andersen, an infectious disease researcher at Scripps Research Translational Institute in La Jolla, Calif., and a co-author of the new study.
Because most cases of Zika go unconfirmed, Dr. Andersen added, the outbreak actually may have comprised tens of thousands of infections.
Cuba saw record tourism in 2017, raising the possibility that many travelers were unknowingly exposed. Some 4.7 million foreign visitors arrived that year, an increase of 16 percent over 2016. More than one million were Canadians.
“If we want to stay ahead of communicable diseases, we need to know where they are and how many cases are occurring,” said Jennifer Gardy of the Bill & Melinda Gates Foundation in Seattle. “For some diseases in some settings, this is pretty straightforward. For others, like Zika, it isn’t.”
Officials at P.A.H.O., an arm of the World Health Organization, blamed the failure to publish timely data on the Cuba outbreak on a “technical glitch.” The information was held in a database, they said, but not visible on the website. By Thursday afternoon, the website had been updated.
Dr. Andersen and his colleagues began tracking Zika’s spread when the mosquito-borne virus first appeared in the Americas in 2015. The epidemic first came to light in Brazil, where babies of some infected mothers were born with severe brain damage. The virus spread swiftly to neighboring countries.
Dr. Andersen and his colleagues collected blood from people infected with the virus. The researchers plucked the virus’s genetic material from the samples and used mutations in the DNA to estimate the timing of Zika’s spread.