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

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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

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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

A child wears a mask near a closed section of a poultry market in Shanghai, where health workers detected the new bird flu, H7N9. Eugene Hoshiko/AP hide caption

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A cockerel walks on a bridge in a residential area of Beijing. The Chinese are beginning to destroy thousands of birds in an effort to stamp out the presumed source of H7N9 infection. Wang Zhao/AFP/Getty Images hide caption

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A child is immunized against polio at the health clinic in a farming village in northern Nigeria. The procedure involves pinching two drops of the vaccine into the child's mouth. For full protection, the child needs three doses, spaced out over time. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

About a third of the world's population is thought to be infected with Mycobacterium tuberculosis, but only a small fraction of people get the disease. NIAID_Flickr hide caption

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Although tuberculosis is declining around the world, drug-resistant strains of Mycobacterium tuberculosis are on the rise. NIAID/Flickr.com hide caption

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