A previously known outbreak of the Zika virus swept across Cuba in 2017, a year after the global health emergency was announced, scientists said Thursday.
So far, the Pan-American Health Organization has no evidence of any Zika infection in Cuba in 2017, much less an outbreak. Following inquiries from The New York Times about a new study published in Cell magazine, employees admitted that they failed to collect 1,384 cases reported by Cuban officials that year.
This figure is a sharp increase from 187 cases confirmed in 2016, and is "in line with the estimates for 201
Because most Zika cases go unchecked, Dr. Andersen added, the epidemic may actually have involved tens of thousands of infections.
Cuba saw record tourism in 2017, raising the possibility for many travelers to be exposed unconsciously. About 4.7 million foreign visitors arrived this year, an increase of 16 percent from 2016. More than one million are Canadians.
"If we are to stay in contagious diseases, we need to know where they are and how many cases are occurring," said Jennifer Gardy of the Bill and Melinda Gates Foundation in Seattle. "For some diseases in some conditions this is pretty clear. For others, such as Zika, it is not. "
PAHO officials, shoulder of the World Health Organization, have accused of not publishing timely data on the epidemic in Cuba for a" technical problem ". A database, they said, but The website was updated by Thursday afternoon.
Dr. Andersen and his colleagues began monitoring the spread of Zika when the mosquito-borne virus first appeared in America in 2015 The epidemic first appeared in Brazil, where babies of some infected mothers ro The virus spread rapidly to neighboring countries
Dr. Andersen and his colleagues collected blood from humans infected with the virus Scientists removed the genetic material of the virus from the samples and used mutations in DNA to
Before Zika was identified in Brazil, scientists discovered that it had been quietly circulating in the country for more than a year. "And at that time it was spread all over the Americas," says Dr. Andersen.
Even in Florida, where the state government maintains careful sections for new outbreaks, Zika arrived three months before it was discovered, scientists learned
In November 2016, the World Health Organization announced that the epidemic was no longer a global emergency in public health. "But we were sitting here with that question," Dr. Andersen recalled. "Are you really done?"
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Scientists continued to track the Zika virus in America. They reviewed data on local outbreaks reported by states to P.A.H.O. They also recounted Zika's confirmed cases of passengers returning to Florida.
In America, both statistics told the same story: The number of Zika cases collapsed toward the end of 2016 and remains low thereafter. But there was one great exception to the data.
In 2016, only a few people who returned to Florida from Cuba were infected by Zika. In 2017, however, Cuba represented 98 percent of Florida's travel-related Zika cases.
This was an unexpected finding. Cuba has a complex public health system and appears to be winning the war on Zika, apparently avoiding epidemics seen in other Caribbean islands.
To verify that the initial results are maintained, Dr. Andersen and his colleagues turned to public health data in Europe and found a similar pattern among Cuba's visitors. The team developed a statistical model to predict the magnitude of the Zika epidemic in a country based on the number of travelers who went to Cuba and returned sick.
They came to the conclusion that the Cuba epidemic in 2017 was "the same size as other Caribbean islands, which means thousands of reported cases," Dr. Andersen said. But since reported cases typically contain about 10 percent of an outbreak, "we're actually talking about tens of thousands of cases."
Researchers also examined blood samples from travelers to Cuba to find out about the epidemic's history and determine that the virus appeared in Cuba in the summer of 2016, there was no patient zero; instead, Zika arrives several times from other islands. It then smoldered, as it had been elsewhere, for a year.
Dr. Andersen suspects that aggressive mosquito control and disease surveillance are holding back the virus while it rages elsewhere in 2016. Other mosquito-borne viruses, such as dengue, also rose through the Caribbean, but Cuba did not see many cases. ,
But after the end of the Zika World Crash in Cuba in 2017, researchers speculated.
"It's easy to miss an epidemic," says Dr. Esther Sabino, director of the Institute of Tropical Medicine at the University of Sao Paulo in Brazil, who did not participate in the new study. Many people who are infected with Zika feel no symptoms, while some only suffer from mild fever for several days.
In many Latin American countries, it is rare for an infection to be confirmed by a complex genetic test, Dr. Sabino said. The methods used by Dr. Andersen's team were an "intelligent way of observing the world" for diseases such as Zika, she added.
Dr. Andersen said the new study adds to the evidence that public health workers must look for signs of outbreaks earlier.
"In many of these cases, we wait until we see strange symptoms and illnesses in patients, and then we realize that we have an epidemic," he said. "If we look at the mosquitoes, we could find it much earlier."