Zika fever
Starting in 2015, there has been an outbreak of Zika virus (meaning that many people have gotten the virus) in Brazil.  Scientists think that when a woman with the Zika virus is pregnant, she can give the virus to her fetus.  Scientists think this can cause microcephaly, a birth defect that causes a baby to have a smaller head than usual.  This can cause intellectual disability and other problems in the brain, like seizures.  Because of this, in January 2016, the United States Centers for Disease Control and Prevention warned pregnant women not to travel to Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, or Puerto Rico, because of the risk of getting the Zika virus there.