A family member holds twins Eloisa (left) and Eloa, both 8 months old and born with microcephaly, during a Christmas gathering. The mother of the twins, Raquel, who lives in Brazil, said she contracted Zika during her pregnancy. Mario Tama/Getty Images hide caption
Illustration by Xaver Xylophon Xaver Xylophon hide caption
They had the right idea: During the worldwide flu epidemic that began in 1918, women in this U.S. office wore cloth masks. Bettmann/Bettmann Archive hide caption
Tucker Lane and his mother, Lynn Cash, sit in the wooded backyard of his home in West Barnstable, Mass. Kayana Szymczak for NPR hide caption
Pig farm workers push live pigs into a large grave in Nipah in 1999. To stop the outbreak, the Malaysian government culled almost 1 million pigs, nearly destroying the country's pork industry. Andy Wong/AP hide caption
Each year thousands of people from around the world tour the Gomantong Cave in Borneo. Although scientists have found a potentially dangerous virus in bats that roost in the cave, no one has ever gotten sick from a trip here. Razis Nasri hide caption
Brazilian howler monkeys are known to carry yellow fever — and can die of the disease. Miguel Rangel Jr/Flickr hide caption
Humans battle the germs. Xaver Xylophon for NPR hide caption
A child with nodding syndrome waits for treatment at an outreach site in Uganda's Pader district. Matthew Kielty for NPR hide caption
Once called the "Dutchmen" because of their large noses and large bellies, proboscis monkeys live only in Borneo. Ecosystems that have a lot of diverse animals, like this monkey, also tend to have a lot of diverse viruses. Charles Ryan hide caption
The Golden Age Of Germs Xaver Xylophon/for NPR hide caption