Why the Zika virus is causing alarm

Global health officials are racing to better understand the Zika virus behind a major outbreak that began in Brazil last year and has spread to many countries in the Americas. Zika is transmitted to people through the bite of infected female mosquitoes, primarily the Aedes aegypti mosquito, the same type that spreads dengue, chikungunya and yellow fever. The Pan American Health Organization (PAHO) said Aedes mosquitoes are found in all countries in the Americas except Canada and continental Chile, and the virus will likely reach all countries and territories of the region where Aedes mosquitoes are found.