Anti-Zika advice applied to a wall in front of a housing project in the Puerta de Tierras section of San Juan, Puerto Rico. This public health message was part of an island-wide effort to stem the spread of Zika. Angel Valentin/Getty Images hide caption
Protest signs at the Florida Keys Mosquito Control District board's meeting Saturday in Marathon, Fla. Greg Allen/Greg Allen hide caption
A vaccine against the Zika virus could help prevent serious birth defects. CDC hide caption
The Zika virus has been largely spread by mosquitoes, but it can also be spread by sexual intercourse. NIAD/Flickr hide caption
A health department microbiologist looks for mosquitoes carrying Zika virus in Hutchins, Texas. LM Otero/AP hide caption
A Florida Department of Health employee processes a urine sample to test for the Zika virus on Sept. 14 in Miami Beach. Lynne Sladky/AP hide caption
Chinashama Sainvilus is one of three babies born with microcephaly at the Mirebalais Hospital in Haiti in July. Jason Beaubien/NPR hide caption
Twin girls born with extremely small heads, shrunken spinal cords and extra folds of skin around the skull. Scientists think this skin forms when the skull collapses onto itself after the brain —€” but not the skull —€” stops growing. The images of the girls' heads were constructed on the computer using CT scans taken shortly after birth. The girls were infected with Zika at 9 weeks gestation. Courtesy of the Radiological Society of North America hide caption
"We believe we have a new area where local transmissions are occurring in Miami Beach," Florida Gov. Rick Scott said Friday about the Zika situation in the state. Alan Diaz/AP hide caption
Containers hold genetically modified Aedes aegypti mosquitoes before being released in Panama City, Panama, in September 2014. Arnulfo Franco/AP hide caption
A health department pickup truck sprays insecticide against mosquitoes in a San Juan, Puerto Rico, neighborhood in January. Alvin Baez/Reuters hide caption
Dr. Christine Curry says Zika virus has been a "game changer" in obstetrics and gynecology. Sammy Mack/WLRN hide caption
The Centers for Disease Control and Prevention is updating its guidelines on preventing transmission of Zika virus via sexual activity. Stephanie Lynn/Flickr Flash/Getty Images hide caption
Canoes, water, mosquitoes — what would summer camp be without them? This year, bug spray will also be in the mix. Mike Powell/Getty Images hide caption
Mosquitoes in traps are transported back to the county's laboratory for analysis. Carrie Feibel/Houston Public Media hide caption
Aedes aegypti mosquito photographed through a microscope. Felipe Dana/AP hide caption
A mosquito control inspector sprinkles larvicide in a storm drain in Miami Gardens, Fla., in an effort to stop the spread of Zika virus. Joe Raedle/Getty Images hide caption
In some parts of the country, this might require bug spray. Steven Errico/Getty Images hide caption
Kelli Glenn holds a photo of her father while he was in the hospital. Meredith Rizzo/NPR hide caption
The Zika virus is spread by mosquitoes, but it can be sexually transmitted as well. Centers for Disease Control and Prevention hide caption
Angelica Pereira feeds her daughter Luiza, who was born with microcephaly, at her mother's house in Santa Cruz do Capibaribe, Brazil. Felipe Dana/AP hide caption
Nadja Bezerra carries her 4-month-old daughter, Alice, who was born with microcephaly, in Recife, Brazil. Dado Galdieri/Bloomberg via Getty Images hide caption