ZVAVAHERA, Zimbabwe (BP) -- The boy carefully climbs out of the desk and makes his way to the large chalkboard at the front of the classroom. After eyeing his teacher, 10-year-old Clive picks up the piece of chalk and fills in the subtraction problem. It may seem small, but Clive's headmaster and teacher agree he is making remarkable improvements. Just a few months earlier, Clive was spending more time in the clinic than he was in the classroom.Like many others in the Zimbabwe village of Zvavahera, Clive is HIV-positive. But Clive's battle with HIV began long before he was diagnosed. Before the disease began to consume his own body -- stunting his growth, making him smaller than other boys his age -- it already was shaping his life. In 2007, AIDS took the lives of both Clive's mother and father, recasting the roles of his family and forcing his 16-year-old sister Mercy into the role of primary caregiver. On their own "When my parents were still alive, everything was better," Mercy says. "They used to assist us and play their role. When they passed away, things became very difficult for us." While other children their age come home from school to fully prepared meals, Clive and Mercy begin the race to complete chores before sunset. The balancing act of cleaning the dishes, sweeping the home, finding firewood, fetching water, searching for food, preparing the meal, finishing homework and other tasks often kept them out of school. In 2011, when Clive received the news he was HIV-positive, he had no idea what it meant, Mercy says. What began as a few missed days of school soon spiraled into months of illness. The decline in health made it impossible for Clive to make the 7-kilometer walk from home to school. "Clive used to be in the clinic every week or every month," Evans Thonolana, a nurse at the Zvavahera Clinic, recounts. On the rare occasions Clive could attend school, his teacher noted that the most he could do was sleep at his desk, unable to even copy notes from the chalkboard onto his paper. Clive's headmaster, Shadreck Makaganise, wondered if the boy would ever recover. "We once went to see him," Makanganise says. "It was terrible, because we never thought he was going to survive." Though Clive had medicine, he lacked the one simple thing needed to sustain his life -- food. As Thonoloana explains, many of the symptoms Clive suffered were caused by his not having enough food for his medicine to be effective.