A man pushes a friend in a wheelchair following an event in Beijing to raise awareness of accessibility issues for the disabled. Ng Han Guan/ AP Photo hide caption

itoggle caption Ng Han Guan/ AP Photo

XMRV, a mouse virus, may be an artifact of laboratory experiments rather than the cause of chronic fatigue syndrome. Whittemore Peterson Institute hide caption

itoggle caption Whittemore Peterson Institute

Nicholas Gibbons, a single amputee with the British Royal Marines team, takes off from the blocks during practice Feb. 21 in Camp Pendleton, Calif., for the inaugural Marine Corps Trials. Fifty athletes were chosen as members of the All-Marine team for the Warrior Games. Michael Goulding/AP hide caption

itoggle caption Michael Goulding/AP

A woman with Alzheimer's disease walks in a corridor at a retirement house in Angervilliers, France, last month. Sebastien Bozon/AFP/Getty Images hide caption

itoggle caption Sebastien Bozon/AFP/Getty Images