(CNN) When Xiao Niao was in high school, her teacher gathered all the girls in her class and told them if they were raped they should take the morning after pill.

That was the limit of her formal sex education. For millions of young Chinese people, it's more than they ever got.

As China marks World AIDS Day Thursday, the effects of that missing knowledge is more evident than ever, with growing numbers of HIV infections and staggeringly high abortion rates.

No protection

In 2015, there were 115,000 new HIV infections in China, according to China's National Center for STD/AIDS Prevention and Control. Of those, 17,000, or 14.7%, were in the 15-24 age group.

While the overall figure is fairly low compared to China's massive population, the year-on-year growth rate among young people is around 35%. As of September 2016, there have already been 13,000 new HIV infections within the 15-24 age group.

Some universities have even installed vending machines selling HIV home testing kits to students.

"Machines alone can't solve the problem unless there's follow-up education to help students," said Xiong Binqi, vice president of the Beijing-based 21st Century Education Research Center.

Xiong praised Chinese universities for making "huge progress in sex education," but warned that "there's a lot to do."

"Sex education faces great challenges in China," said Jing Jun, a professor of sociology at Beijing's Tsinghua University.

"At Tsinghua, students take sex education classes where they learn basic knowledge about sex safety, condom use, etc. As far as I know, this is the first time most of my students have ever taken such a class."

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Abortion as birth control

Some sex educators, frustrated at the lack of official action, are taking it on themselves to spread the message via apps and social media such as Buzz and Bloom and Yummy

Launched last year, Buzz and Bloom (蜜丰兰花) provides sex education and health advice over messaging app WeChat.

Shanghai-based Buzz and Bloom provides free sex education and advice via WeChat.

Co-founder Stephany Zoo, 24, came up with the service after she visited an abortion clinic in Shanghai with a friend and discovered how unprepared for the procedure several of the young women in the waiting room were.

"So many of the girls were going in for abortions without having any idea what was going to happen," she said.

For many young women, abortion is their primary form of birth control.

According to official statistics, more than 13 million abortions are performed in China every year, a figure experts say is a vast underestimation, as it does not include non-surgical abortions or those carried out in unlicensed clinics.

"Many women have abortions because they lack basic sex education, especially contraceptive education," Yummy founder Zhao Jing said.

"They think having an abortion is like taking a nap, which is how it is described in adverts."

Sex talk

Yummy founder Jing Zhao in her office in Beijing.

Zoo and Zhao's start-ups, along with a handful of other groups, are working to create spaces online and off where young Chinese people can discuss all things sex -- something that can be an uphill struggle.

"Even talking about things like periods they would be immediately uncomfortable," Zoo said. "There's still this culture of shaming when it comes to sexual health and bodies."

With nowhere else to turn, Zhao, 33, said young people often look for information and advice in the wrong places.

"Men learn from Japanese pornography. Women learn from having one night stands," she said. "The attitude is like 'ok, just try it,' without contraception."

Even some women who know better can be "too shy" to tell their partners to wear condoms, she said. "China still has the stereotype where men are the conqueror and women are submissive in sex."

This can lead to pointless risks, Zoo said. "I had a girl tell us once that her boyfriend said if she held her breath during sex she couldn't get pregnant."

Volunteers hand out condoms in a subway station in Wuhan on World AIDS Day.

Limited action

While concerns over rising HIV infection rates have led to some official action, Zhao said that too often government interest spikes around high profile events like World AIDS Day on December 1, and doesn't translate into long-term change.

Wu Zunyou, director of the National Center for AIDS/STD Control and Prevention, said that while HIV infection rates among college students have risen in recent years, it is still "not that high."

"Many teenagers and students have not fully understood the gravity of AIDS, and take it for granted that it is irrelevant to them," he said.

Tsinghua professor Jing said that young gay men are particularly at risk, as they face a double stigma.

"No effective measures have been taken by the Chinese government to curb the high HIV/AIDS contraction rates among homosexuals, despite being effective at tackling infection rates among prostitutes, blood-sellers and drug users," he said.

This because the government often takes a hands off approach to LGBT organizations, even those engaged in public health initiatives, Jing said, leaving them without much-needed funding or support.

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Progress

As they prepare for official interest in promoting safe sex to wane again, women like Zoo, Zhao and Xiao Niao are only just getting started.

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Zhao said educators are expanding from targeting young people to also working with parents to help them talk to their kids about sex and break the cycle of sex-ed silence.

Now 30, Xiao Niao has attempted to bridge the gap within her own family, with limited success. "I spoke to my brother about how he needs to wear condoms," she said. "He immediately left the room."

In Shanghai, Buzz and Bloom has begun holding offline events, combining the sharing of funny sex stories with open, no-holds-barred discussions of sexuality and sexual health.

"It's about making sex fun and accessible and not something that's being held on a pedestal," Zoo said.

"If you think when you have sex your world is going to explode and change, obviously you're never going to have great sex."