zika

Particles of Zika virus are colored red in this transmission electron micrograph. CDC hide caption

Dr. Tom Frieden (left), director of the Centers for Disease Control and Prevention, testifies about Zika virus with Dr. Anthony Fauci (center), director of the National Institute of Allergy and Infectious Diseases, and Dr. Ariel Pablos-Mendez, assistant administrator of the U.S. Agency for International Development's Bureau for Global Health, on Capitol Hill on Feb. 10. Nicholas Kamm/AFP/Getty Images hide caption

Jamaica's Ministry of Health released a reggae music video about how people can protect themselves against the Zika virus. YouTube hide caption

Brazilian soldiers prepare for an operation to fight the Aedes aegypti mosquito, vector of the Zika, Dengue and Chikungunya viruses, in Sao Paulo, Brazil on February 3. The operation on Saturday will include 220,000 soldiers passing out pamphlets; they hope to reach 3 million homes. Nelson Almeida/AFP/Getty Images hide caption

Sexual transmission of Zika virus has happened, scientists say, but it appears to be rare. Davide Doisneau/Flickr RF/Getty Images hide caption

The Zika virus, once thought to be spread only through mosquito bites, was sexually transmitted to a person in Texas, health officials say. Marvin Recinos/AFP/Getty Images hide caption

Dr. Margaret Chan, director-general of the World Health Organization, and Dr. David L. Heymann, WHO assistant director-general, announce the global emergency during a news conference Monday in Geneva. Fabrice Coffrini/AFP/Getty Images hide caption

This is a partial view of the tennis center at Olympic Park in Rio de Janeiro. The International Olympic Committee is sending an advisory to participants in the 2016 Summer Games on how to deal with the mosquito-borne Zika virus. Leo Correa/AP hide caption