Aedes aegypti mosquitoes are displayed at an exhibition on Jan. 28 in Brazil. The mosquitoes can be carriers of the Zika virus. Several cases of the virus have spread to Puerto Rico.
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Nancy Writebol, a missionary who recovered from Ebola she contracted in Liberia in 2014, told a reporter last July that she was still experiencing knee pain and hadn't fully regained her energy.
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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.