Sheva Alomar is an operative of the West African Bioterrorism Security Assessment Alliance (BSAA), an organization formed by the U.S. federal government along with the United Nations Security Council and the fictitious Global Pharmaceutical Consortium to combat biohazardous threats around the world. She made her first appearance in Resident Evil 5 working with Chris Redfield as his new partner. At the age of eight, Sheva's parents died in what appeared to be a factory accident, she was taken in by her uncle to live with him and seven other children. Eventually Sheva ran away from her uncle's home and was found by a truck driver who took her in and looked after her, but unknown to Sheva, he was part of a guerilla group. Sheva later joined the group, and soon learned that what happened to her parents was much more than just an accident, the factory was the location of a final test of one of Umbrella's bio-organic weapons (BOWs). With the help of the local government, Umbrella destroyed Sheva's village and all inhabitants after the test was complete. Sheva remained with the guerillas through her childhood. When she reached the age of 15, she was contacted by American operatives to stop Umbrella selling a BOW to the guerillas. With Sheva's help, the operatives stopped the deal and apprehended the Umbrella salesman. The man who initially contacted Sheva offered her a chance to start her life again in America. Sheva accepted, within months, Sheva was speaking English like a native and enrolled in a university two years later. After graduation, her benefactor suggested she join the BSAA. While Umbrella had dissolved years before this, Sheva's hatred of Umbrella and all others like them led her to join the BSAA. Sheva was assigned to Josh Stone's unit for eight months for training in which she excelled. Upon completion of her training, BSAA chose her to become an operative. She was assigned to the West African BSAA department soon after. She was put alongside Chris Redfield at the start of the Kijuju mission as his new partner, after the loss of his previous partner, Jill Valentine.
Source: Wikipedia, "List of Resident Evil characters", available under the CC-BY-SA License.