Georgia now has four new travel-related cases of the Zika virus, bringing the total number of confirmed cases in the state to six.

The Georgia Department of Public Health received the test results on Tuesday from the Centers for Disease Control and Prevention for four Georgia travelers. The health department would not identify the men and women in any way other than saying they had visited areas of the Americas where the virus is rampant.

Growing evidence suggests Zika is the cause of microcephaly, a devastating birth defect that leaves newborns with underdeveloped brains and unusually small heads. None of the Georgia travelers was pregnant.

Last month two other Georgians were confirmed to have had Zika. They contracted the disease while traveling as well. The CDC has issued travel advisories warning pregnant women not to visit countries with active Zika outbreaks, such as Brazil which has been the epicenter of the outbreak in the Americas. The virus can also be transmitted sexually, but is primarily contracted through mosquito bites.

There is growing concern that the virus will spread rapidly in the Southern United States as temperatures rise and mosquito populations explode.