When Emmanuel Ikubese first saw the show MTV Shuga, he was a university student and an aspiring actor. Like many fans, he was hooked.

There's a lot to like about the show: There's future Oscar winner Lupita Nyong'o in her breakout role, playing a go-getter juggling school, work and multiple lovers. There's drama, intrigue and, in the first two seasons set in Nairobi, glimpses of a vibrant nightlife: banging beats, fly fashion and sexy dancing.

But for Ikubese, there was something else. "I was watching it and I was like, 'Man, this show is so deep,'" he says. The show portrays several characters coping with the AIDS epidemic. "I don't know why, but I had never been tested at that point," Ikubese says. "It's just something nobody talked about." So he got tested (results were negative) and encouraged his friends to, as well.

MTV Shuga — the name is pan-African slang for a woman with a cool vibe — has launched its fifth season this spring. And Ikubese is one of its stars. He plays mega-hunk club promoter and reformed bad boy Femi.

What he knows now is that Shuga isn't the average teen drama. It's also a public health intervention. Folded into each soapy, 30-minute episode are messages about how and how often to get tested for HIV, as well as scenes that dispel common misconceptions about the disease.

Commercially, it's doing pretty well. TV channels and radio stations in 42 African countries have signed up to broadcast the latest season of Shuga, and by MTV's count, the show has reached 719 million people worldwide who've either watched or listened to it through local entertainment networks or online on YouTube. In South Africa alone, Shuga seasons 3 and 4 were the number one drama show on the country's biggest TV channel, SABC1.

And there are signs that the health messaging is sinking in as well. A World Bank study published online last month found that six months after watching Shuga, young viewers were twice as likely to get tested for HIV as those who hadn't seen the show.

Those results validate what Georgia Arnold, the founder of MTV's Staying Alive Foundation, the nonprofit that helped create the program, has been working toward her whole career. "I think once kids recognize themselves and their own behavior on screen, that's when we get to see them questioning their actions," she says. "So that's why for us, the most important thing always is we start with young people."

For this latest season, "before we started writing anything, we did a panel session with a group of kids in a township outside of Johannesburg," Arnold explains. "Then we took their stories and turned them into a storyline," she says, with the help of local doctors and counselors to make sure the health messaging was accurate. (U.S. viewers can see the new season on YouTube)

Shuga also employs its writers, actors and production company from the city where it's set. That was Nairobi for two seasons, then Lagos, Nigeria for another two seasons, and now Johannesburg. Each season incorporates the language, music, culture and color of its local setting.

"That's important," explains Abhijit Banerjee, an economist at MIT who helped evaluate the public health impact of Shuga for the World Bank. In order to influence young people's behavior, Shuga had to show them characters they could relate to.

To test the effectiveness of the show's health messaging, Banerjee and his colleagues recruited 5,000 18- to 25-year-olds across Nigeria. They screened the show to two-thirds of them — while the rest saw a different Nigerian TV show. Before and after the screenings, researchers questioned all the participants to gauge their knowledge and understanding of safe sex, HIV and domestic violence. Six months later, they asked everyone to come back, to see if any lessons from Shuga had stuck.

Those in the group that had watched Shuga were twice as likely to be tested for HIV than those who didn't watch. Even though the majority of participants still weren't getting tested, researchers say that's a sign that the message is sinking in.

The study also found that the number of chlamydia infections was 58 percent lower among women who watched than among those who didn't watch. And the Shuga viewers were 14 percent less likely to have concurrent sex partners.

Not everything about Shuga went over as well as the researchers had expected. The show had the unintended effect of making viewers sympathetic toward a character who committed domestic violence. That may have had to do with the way a subplot about a character who beats his girlfriend was presented, Banerjee says.

In Shuga, the character who hurts his girlfriend is, by many accounts, a lovely guy. "But his boss is not nice to him, and he's not as successful as he'd like to be," Banerjee says. He's not happy, and his partner isn't as supportive as he'd like her to be.

"So for some viewers, a key moment when he ends up hitting her was hard to interpret," Banerjee says. Of course, nothing justifies domestic violence, and the show writers will have to think hard about how to make that clear going forward, Banerjee says.

Overall, the World Bank study "makes a really compelling case for the show," says Suruchi Sood, a public health researcher at Drexel University who wasn't involved with the study.

Sood says she'd love to see more in-depth analysis of Shuga's public health impact. The results confirm the research on how young people learn: Stories are a safe, accessible way to get information out to adolescents who might otherwise tune out important messages about sexual health.

"And the fact that [Shuga is] doing it at this global scale is quite amazing," Sood says. "I can't think of any other public health intervention that can reach so many people."

Of course, for Emmanuel Ikubese, all this makes perfect sense. After all, the show convinced him to go get tested for HIV and it has also helped him reconsider some of his underlying attitudes toward the disease, he says.

When Ikubese found out that the character he plays would contract HIV in season 3, he was initially hesitant. "I was really worried about it because, you know, people often confuse actors with the characters they play," he says. And there's a lot of stigma associated with being HIV positive in Nigeria. And he worried that the character would be no fun to play. Growing up, if he saw someone on TV or in the movies who had HIV, they were usually weak and sickly.

"Then I saw the script," he says. His character Femi would remain hunky as ever, and he'd find a girlfriend who supports him. "I realized that this was about passing the message that you can have HIV and you can you can still be looking good, you can be healthy and you can still have relationships," he says. "And funny enough, after the show came out, I got more positive responses from fans than negative responses."

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