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It's 3:30 a.m., and Jose Wesley Campos giggles nonstop as his mother plays with the toddler's thick glasses while preparing to take him to a doctor's appointment three hours away. "Sometimes, it is as if he swallowed a clown," said his mother, Solange Ferreira. That is a stark contrast from a few years ago, when Jose, who was born with an abnormally small head amid an outbreak of the Zika virus in northeast Brazil, would shriek uncontrollably. Desperate, Ferreira would calm the boy by putting him in a bucket of water. (6/6)

On Tuesdays, 18-month-old Joaquim Santos spends an hour sitting by himself in a corner of a special needs classroom in this small city in northeast Brazil, one of the country's poorest regions and one hit hard by the Zika virus. Two harried teachers look on as other toddlers play around Joaquim, who has severe developmental delays after being born with a small head. As limited as Joaquim is in the early education classroom, his family and doctors say he is lucky to be there. (6/6)

Three years ago, Brazil experienced a major Zika outbreak that led to the revelation that the virus can cause severe birth defects in babies whose mothers were infected during pregnancy. Here's a look at what scientists know today about Zika and its effect on developing fetuses. (6/6)