On the list of pathogens (from left): Staphylococcus aureus (causes skin infections, pneumonia, bloodstream infections), Pseudomonas aeruginosa (causes blood infections, pneumonia, infections after surgery) and Neisseria gonorrhoeae (causes the sexually-transmitted disease gonorrhea). NIAID; Scott Chimileski and Roberto Kolter, NIH Image Gallery/Flickr; NIAID hide caption
Tamil and Sinhalese workers pick tea on Amba Estate in the early morning. Victoria Milko for NPR hide caption
Rai competes at the 2014 Manaslu Trail Race, which passes through Nepal's Himalayan landscapes. Richard Bull 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
Lucia Adeng Wek holds her 3-year-old son, Wek Wol Wek, who suffers from malnutrition. They're at a clinic in South Sudan run by Doctors without Borders and were photographed on October 11, 2016. Albert Gonzalez Farran/AFP/Getty Images hide caption
Andie Vaught grasps a stress toy in the shape of a truck as she prepares to have blood drawn as part of a clinical trial for a Zika vaccine at the National Institutes of Health in Bethesda, Md., in November 2016. Allison Shelley/The Washington Post/Getty Images hide caption
Wedding guests dance at a New Delhi celebration. Daniel Berehulak/Getty Images hide caption
A typical meal in the Democratic Republic of Congo consists of greens, fufu - a starchy ball made from cassava flour - and meat, such as freshwater fish. Amy Maxmen for NPR 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
Sundaygar Moses, now 12, was suffered a gunshot wound as an infant. Due to an infection, his right leg had to be amputated beneath the knee. His new prosthetic is a close match to his skin tone. Carielle Doe for NPR hide caption
Mumbai, India (2007) Courtesy of Martin Roemers 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