CDC wants all pregnant women tested for Zika in Fla.

The CDC had asked doctors in Florida to test all pregnant women in the state for the virus - regardless of whether they were in an area known to have Zika, and regardless of whether they had symptoms.

Doctors there will closely follow these women.

The biggest concern with Zika is that it can cause devastating birth defects, including microcephaly, which affects the brain and nervous system.

Pregnant women in South Florida, where Zika has been found, are urged to wear insect repellent and limit their time outside.

Meanwhile, there is sobering news in Brazil.

Researchers there say the rate of birth defects involving the nervous system nearly doubled across the country since the Zika virus hit.