The Zika virus, once it established a beachhead in Brazil, swept across the country at an average rate of about 26 miles a day, according to an international team of researchers.
The researchers, from Boston's Children's Hospital, Harvard Medical School, the University of Washington, McGill University and the Brazilian Health Ministry, said they used computer models that were used to estimate how Ebola spread in West Africa. Their "Reconstruction of Zika Virus Introduction in Brazil" appears on the CDC's website.
The U.S. Centers for Disease Control and Prevention has said repeatedly that the virus is unlikely to spread the same way in the U.S. That's largely because mosquitoes that carry Zika aren't found throughout the nation, and the virus is spread primarily through two specific mosquitos. But is also has a lot to do with modern conveniences, such as air conditioning, not prevalent in some outbreak regions.
The researchers began looking at the introduction of the virus to the Americas through the Easter Islands. Though they don’t know exactly who was Brazil’s patient zero, or how the transfer occurred, the first cases began showing up in Brazil in January 2015.
It showed up first in the central, western and northern regions of Brazil, just a few cases initially. In 29 weeks, it had spread across nearly the entire country. On average it spread about 26 miles a day, according to the researchers’ model. To compute the spread, researchers used data from the Brazilian Ministry of Health, which gathered the number of reported cases of Zika from municipal health departments and hospitals.
Zika has since spread through the Americas and is now a problem in Singapore. The U.S. saw its first cases of mosquito-borne Zika in Miami in June. So far, Florida has 65 cases of the virus, not associated with people who've traveled to other parts of the world experiencing a Zika outbreak. All but seven of the Florida Zika cases are in the Miami-Dade area. Puerto Rico has experienced a serious Zika outbreak with an estimated 25 percent of the population likely to contract it by next year, CDC officials have said.
The virus causes devastating birth defects, including microcephaly. Most people don’t know they have the disease, as only one in five people have symptoms which usually last a week to 10 days.
The Aedes aegypti and Aedes albopictus mosquitoes are the primary transmitters of Zika. But as time went on, researchers discovered the disease could be sexually transmitted as well.
While federal health officials here are worried about the spread of Zika, they have said it’s unlikely the rate of infection in Brazil and Puerto Rico will be replicated on the U.S. mainland. Zika spread quickly in poorer areas of Brazil where air conditioning, window screens and effective mosquito control programs weren’t abundant. Even in Puerto Rico, the government has stepped up efforts to install window screens in homes and has tried an aggressive mosquito abatement program.
To date, 18,833 cases of Zika, both travel related and mosquito-borne have been reported in the U.S. and its territories, according to the CDC.
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