In response to reports in Brazil of microcephaly (a birth defect where a baby's head is smaller than expected) in babies of mothers who were infected with the Zika virus while pregnant, the Centers for Disease Control and Prevention (CDC) has issued a travel alert for people traveling to 22 countries where Zika virus transmission is ongoing. Visit the CDC's Travelers Health website to see if any country you plan to visit has any travel health notices. The Zika virus is spread to people through mosquito bites. The most common symptoms of Zika virus disease are fever, rash, joint pain, and conjunctivitis (red eyes). Severe disease requiring hospitalization is uncommon. Learn how to prevent mosquito bites here.