They are the innocent and often silent victims of a crime that too often goes unreported in rural parts of China due to children's shame and the social stigma attached to sexual abuse. Child sex abuse is often rampant in villages where parents are often thousands of kilometers away laboring as migrant workers, unable to keep a watchful eye on their children.

One of the most shocking cases emerged last year, when a 12-year-old girl named Xiaoli (pseudonym) from Guxian township of Yanshi in Henan Province was found to be four months pregnant. Xiaoli's sole guardian was her 65-year-old grandmother.

Xiaoli had been sexually abused by a man surnamed Li, who lived in the same county. Li molested Xiaoli repeatedly at his home, threatening to throw her into a river if she ever told anyone of the abuse.

Scratching the surface

Xiaoli's case was only the tip of the iceberg of Guxian's child sexual abuse epidemic. An official from the local procuratorate told the China Youth Daily that 19 similar cases were reported in Guxian last year alone.

In East China's Anhui Province, 43 students aged under 13 from four different counties were reportedly sexually abused by their teachers last year. Most victims were children of migrant workers in other cities.

The All-China Women's Federation and the People's Procuratorate in South China's Guangdong Province conducted joint research on children living in parentless homes and found that 2,506 children under 18 had been sexually abused over the last three years, with more than half of the victims under 14, the Guangzhou Daily reported.

"Child sex abuse is probably more common than statistics indicate," Wang Ling, researcher with the Family Education Professional Commission at the Chinese Society of Education, told the Global Times. "It is humiliating for children to be sexually abused in Chinese society, especially for victims from conservative, rural areas."

Figures from the National Statistics Bureau revealed that last year there were 158.6 million migrant workers, up 3.4 percent from 2010.

Left-behind, lacking supervision

These children, who must settle for reuniting once a year with their parents during Spring Festival, have become collectively known in China as the "left-behind children."

China is home to 58 million left-behind children, 70 percent of whom are cared for by their grandparents and 5 percent of whom live on their own, according to the All-China Women's Federation.

"In the countryside, grandparents often aren't as watchful over children as parents. This largely increases the risk [of sexual abuse]," Wang said.

According to a survey of more than 7,000 people conducted in five major metropolises including Shenzhen, Beijing and Guangzhou, over half of respondents said they were raised by their grandparents.

"I was a left-behind child and suffered the loneliness of living without my parents, but now my daughter is enduring the same experience," Wei Chulin, a 30-year-old migrant worker in Shenzhen originally from Maoming, Guangdong Province, told the Global Times.

Wei's concerns for his 7-year-old daughter have heightened since a spate of sexual assaults on children last year in Maoming.

Sun Daqiang, a teacher from the coastal Guangdong town, was arrested after sexually abusing several of his students aged between 9 and 11 for years. The plight of his victims, all who remained silent throughout their abuse, only came to light when a video of Sun molesting a child shot on his cell phone was exposed.

Wei, like many local parents, was shocked at the news. "I have been urging my daughter not to let strangers ever touch her inappropriately," he said, adding that taking his daughter to Shenzhen isn't practical because she cannot enroll at a public school without a local hukou (household registration).

Research conducted by child advocacy website chinachild.org found over 80 percent of child molesters are known by their victims and their families, with most aged between 50 and 82. One factor that contributes to sexual abuse of children and cases being unreported is that children are often unaware about being cautious around strangers.

"In some rural towns, girls have no idea about how to protect their bodies," Wang said.

Awareness through education

Left-behind children are also often naïve about sex, partly because sex education isn't compulsory at schools and grandparents can be reluctant to teach it to their grandchildren.

Wang's research team formed by the Chinese Society of Education earlier this year went to Guangping, a county densely populated by left-behind children, in Central China's Hebei Province to investigate if sexual abuse was a problem.

One student, an 11-year-old girl, wrote of her experience of being sexually abused. She had originally thought there was nothing wrong with an older man kissing and spanking her and, even though it had made her uncomfortable, she didn't tell her grandparents or anyone else.

Wang said challenges in investigating sexual abuse in rural areas include victims' humiliation and reluctance to talk about it, as well as the fact many children aren't aware it's inappropriate.

"We wanted to teach children sex education, but were questioned by parents and the schools who asked why we weren't trying to improve their grades instead," Wang said.

Researchers also found that when calling home, many migrant worker parents mostly ask about their children's studies, with few concerned about their mood or behavior outside of school.

Even parents who learn that their kids have been sexually abused are reluctant to prosecute offenders amid fear that "everyone will know about the family's scandal," a prosecutor who asked to remain anonymous from Zixin, Hunan Province, told the Global Times.