Africa's porous borders and location have made it an attractive destination for drug traffickers. Health and government officials worry how this trend affects the growing rate of HIV infection on the continent. In Senegal, drug users have emerged as one of the highest risk groups for HIV infection. In this first part of a five-part series on the most vulnerable groups to HIV infection in Africa, Phuong Tran reports from Dakar.

When he was 15 years old, Moussa Sanganra lived with his uncle, a fisherman. Sanganra remembers how his uncle frequently used drugs, which he kept in his bedroom.

Sanganra -- now 25 -- says he started using drugs because he was always around them. At the time, he says he did not know he was at risk for HIV from sharing old and possibly infected needles.

It was only much later, after he had left the hospital for drug-induced hallucinations, when he learned of the link between drug use and HIV infection.

He still has not taken an HIV test, although he says he is curious.

Chiekh Diop, president of the Association of Non-Profits Against Drugs, says there are many HIV positive cases among drug users. But, officials do not know the numbers infected.

And because the community is still being identified, Diop says HIV prevention services are still lacking.

"HIV prevention was not a priority in the beginning," he said. "It was only when we started seeing more HIV positive cases, about three years ago, that we made the connection."

Diop says some health officials and research groups are planning studies of drug users in Senegal. With these results, Diop says the government can explore new prevention programs other countries have long used, including giving drug users new needles to prevent spreading the virus through old, infected needles.

But he says Senegal still has a long way to go.