A virus called XMRV was linked to chronic fatigue syndrome in a study published in Science in 2009. Now that paper has been withdrawn. David Schumick and Joseph Pangrace/Cleveland Clinic Center for Medical Art & Photography hide caption

itoggle caption David Schumick and Joseph Pangrace/Cleveland Clinic Center for Medical Art & Photography

Often times, bed bug infestations stem from a succession of inbreeding from one female's progeny. Orkin, LLC/PR NEWSWIRE hide caption

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H5N1 avian flu viruses (seen in gold) grow inside canine kidney cells (seen in green). Cynthia Goldsmith/CDC hide caption

itoggle caption Cynthia Goldsmith/CDC

One recent study found that people were able to burn up an extra 450 calories a day with one hour of moderate exercise. That can include walking briskly, biking or swimming.

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