SHANGHAI, Dec. 1, 2012 (Xinhua) -- A volunteer (R) helps her colleague put on a red ribbon during an activity to mark the 25th World AIDS Day in east China's Shanghai Municipality, Dec. 1, 2012.The World AIDS Day, which was started in 1988, is observed each year on December 1 to raise the awareness of AIDS caused by the spread of HIV infection. (Xinhua/Ding Ting)