Sitting in his dimly-lit office in the Nigerian capital of Abuja, surrounded by files and boxes of condoms, matchmaker Ugochukwu Michael talks passionately about the part he has played in the marriages of around 100 couples in recent years.

While the popularity of dating apps and websites may make Michael's efforts to play Cupid seem old-fashioned, his matchmaking service stands out from the rest.

All of his clients are living with HIV.

"Sometimes, I spend days without sleeping," he said, his phone ringing nonstop as he explained how most calls come in the middle of the night when it is cheaper to call.

The 45-year-old started his service in 2012 with the desire to help those he describes as Nigeria's "rejects" after becoming disillusioned with widespread stigma toward people with HIV.

Michael says he has some 7,000 clients on the books, ranging in age from 19 to 72. Six in seven of them are women.

Free for unemployed

He charges a one-off fee of 2,000 naira ($6) for people who work, but his service is free for the unemployed.

"You will see a lot of improvement," Michael tells one caller. "Let's see how it will be before the end of the month."

The prevalence of HIV among adults in Nigeria is relatively low for sub-Saharan Africa, around one in 30 compared to one in five in South Africa, said the UN AIDS program UNAIDS.

Yet discrimination toward Nigeria's some 3.5 million HIV-positive people is rife, and many struggle to enter university or find work, health experts and human rights activists say.

"Stigma is the obstacle to achieving the 90-90-90 agenda," said John Idoko, director general of Nigeria's National Agency for the Control of AIDS.

By 2020, UNAIDS wants 90 percent of people with HIV to know their status, 90 percent of diagnosed people to be on treatment, and 90 percent of those on treatment to have suppressed levels of the virus in their bodies.

After a failed attempt to migrate to Europe six years ago and the loss of his life savings from his job as a technician, Michael decided to volunteer with a Catholic organization.