A woman is vaccinated at a health center in Conakry, Guinea, during the clinical trials of a vaccine against the Ebola virus. Cellou Binani /AFP/Getty Images hide caption

An Ebola burial team dons protective clothing before collecting the body of a woman who'd died from the virus in her home in a suburb of Monrovia, Liberia's capital. John Moore/Getty Images hide caption

Emmie de Wit, who usually works in a Biosafety Level 4 Lab, spent time in less secure labs in Liberia during the Ebola outbreak in West Africa. Above, she prepares to test Ebola patient blood samples. Courtesy of NIAID hide caption

A worker stands near dividers intended to separate patients in an Ebola treatment facility under construction in the Port Loko district of Sierra Leone in 2014. David Gilkey/NPR hide caption

Omu Fahnbulleh stands over her husband after he staggered and fell, knocking him unconscious at an Ebola ward in Liberia in 2014. John Moore/Getty Images hide caption

An Afghan child was one of Gilkey's "little buddies." David P. Gilkey/NPR hide caption

A mosquito control inspector in Miami-Dade County, Fla., looks for mosquito larvae in water from a storm drain. Joe Raedle/Getty Images hide caption

The mystery disease in South Sudan has not been identified but is known to cause fever and unexplained bleeding. Above: an image of another hemorrhagic fever, Marburg virus, made with an electron microscope and then colorized. BSIP/UIG/Getty Images hide caption

Margaret Chan (left), director general of the World Health Organization, is among the dignitaries visiting a military base in Conakry, Guinea, on a tour of west African countries affected by Ebola. Also pictured: Guinean President Alpha Conde (fourth from right) and U.N. Secretary General Ban Ki-Moon (right). BINANI/AFP/Getty Images hide caption

People in Pinar del Rio, Cuba, make their way through a fumigation fog that's meant to kill the mosquito that transmits the Zika virus. Ramon Espinosa/AP hide caption

In November 2014, a worker stands by dividers to separate patients in an Ebola treatment facility under construction in the Port Loko district of Sierra Leone. David Gilkey/NPR hide caption

Mamuedeh Kanneh (right) was married to the man who brought Ebola to Barkedu, Liberia, a village of about 6,000. He died of the virus. She now cares for her children as well as children who lost their parents to the disease. John W. Poole/NPR hide caption