A blood test developed by Harvard researchers checks for evidence of past infection with more than a thousand strains of virus, from about 200 virus families. The swine flu virus shown here, A/CA/4/09, rarely infects humans.
C. S. Goldsmith/CDC
Augustine Goba (right) heads the laboratory at Kenema Government Hospital in Sierra Leone. He and colleagues analyzed the viral genetics in blood samples from 78 Ebola patients early in the epidemic.
Biologist Rob Knight, co-founder of the American Gut Project, recently moved the project to the University of California, San Diego's School of Medicine.
Casey A. Cass/University of Colorado
A woman protects her child's face in Managua, Nicaragua, as health workers fumigate for mosquitoes that carry chikungunya. The virus started spreading through Nicaragua and Mexico in the fall.
We are all Russian nesting dolls: Our intestines house many bacteria, which house many viruses. These so-called bacteriophages are likely as important for our health as the bacteria they live in.
Lisa Brown for NPR
France has banned imports of live pigs and other products from the U.S. to keep out a virus that has killed more than 4 million pigs in the U.S. Here, young pigs look out of a pen at a North Dakota hog farm in a 2005 file photo.