Health workers vaccinate a boy against polio at a May immunization drive in Mogadishu, Somalia. Farah Abdi Warsameh/AP hide caption

itoggle caption Farah Abdi Warsameh/AP

Saudi men walk to the King Fahad hospital in the city of Hofuf on Sunday. In eastern Saudi Arabia, where outbreaks of the MERS virus have been concentrated, people have resumed their habits of shaking hands and kissing. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Spinal MRIs similar to these found infections that many patients hadn't realized they had. Stefano Raffini/iStockphoto.com hide caption

itoggle caption Stefano Raffini/iStockphoto.com

A woodcut from the 1800s, Healing the Lepers, depicts the common tableau of Jesus healing a leper as his disciples look on. Images from the History of Medicine hide caption

itoggle caption Images from the History of Medicine

Boys at the L'Ecole Les Freres Clement elementary school in Jacmel, Haiti, line up to take deworming pills that protect against elephantiasis. Maggie Steber for The Washington Post/Getty Images hide caption

itoggle caption Maggie Steber for The Washington Post/Getty Images

The Centers for Disease Control and Prevention says doctors should prescribe Truvada, a once-a-day pill for HIV, to help prevent infections in IV drug users. Jeff Chiu/AP hide caption

itoggle caption Jeff Chiu/AP

Here's the coronavirus that appears to have originated in the Middle East and has caused severe illnesses in people living there and in Europe. AP hide caption

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A nurse walks towards the Roger Salengro Hospital in Lille, France, where two patients were diagnosed with a coronavirus related to SARS. Michel Spingler/AP hide caption

itoggle caption Michel Spingler/AP

A baby receives a polio vaccine at the Medina Maternal Child Health center in Mogadishu, Somalia. The country has one of the lowest immunization rates in the world. Ben Curtis/AP hide caption

itoggle caption Ben Curtis/AP

Fungi (cyan) surround a human hair within the skin. A study in the journal Nature shows the population of fungi on human skin is more diverse that previously thought. Alex Valm, Ph.D. hide caption

itoggle caption Alex Valm, Ph.D.

Luke Tanner, 7, gets vaccinated for measles at a clinic near Swansea, Wales, in April. Wales is at the center of a measles outbreak that has been linked to one death. Geoff Caddick/AFP/Getty Images hide caption

itoggle caption Geoff Caddick/AFP/Getty Images

More than a hundred different species of Anopheles mosquitoes can transmit malaria to people. Adam Cole/NPR hide caption

itoggle caption Adam Cole/NPR

Influenza covers it's shell with two types of accessories: the H spike, blue, and the N spike, red. Here the flu particle is sliced open to show its genetic material. Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases hide caption

itoggle caption Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases