The Zika virus may cause birth defects — and experts think it’s coming to the US

The Zika virus, a rare tropical disease that’s causing a panic in Brazil — because it may lead to babies being born with abnormally small heads — has now made its way to Puerto Rico. And experts fear the United States could be next.

Until last year, the Zika virus, which is spread by mosquitoes, was mainly confined to Africa and Asia. But in 2015 the disease made the leap to the Western Hemisphere, affecting more than a million people in Brazil. It’s since spread to Colombia, Venezuela, Mexico, and nine other countries. Last week, the first confirmed case in Puerto Rico was reported.