As part of a Dialogue of Civilizations program to South Africa some two years ago, Northeastern University student Tim Spittle visited an orphanage for children who lost their parents to HIV/AIDS. The experience, he said, shaped his humanitarian calling, and convinced him to pursue a career in raising awareness of public-health crises.

Now a junior, he is one of six college students in the United States who is participating this summer in the Ride Against AIDS 2011, a 4,000-mile bicycle trek from California to Boston aimed at raising money for Partners in Health’s HIV/AIDS efforts in Rwanda.

“When we talk about what we’re doing and about our mission, people have been really touched by this and they think twice about what they can do,” he said.

Spittle, who competed in two triathlons last year, is well equipped to handle the physical stress of the bike ride, which requires cyclists to pedal some 90 miles per day.

But the hardest part of the odyssey is spreading the word at each of their stops, where he and his team members e-mail Rotary Clubs, the local paper and the mayor’s office, and set up interviews, presentations and meetings with youth groups.

As Spittle put it, “We do whatever we can do.”

Since its inception in 2007, Ride Against AIDS — run by the nonprofit organization FaceAIDS — has raised more than $80,000. Spittle’s team expects to raise an additional $20,000 over the course of their ride, which is expected to end in Boston on August 18.

Spittle’s summer on a bike dovetails with the business major’s interest in Northeastern’s Social Enterprise Institute, through which he is taking classes in social entrepreneurship.  The institute enables students to become globally aware business leaders by providing them with opportunities to help the poor in developing countries build their own small businesses through micro-financing.

“This is my big step toward finding a way to focus my career on the public-health sector,” he said.