She still isn't sure how she contracted the virus her mother died from AIDS-related complications when she was six years old, and she slept with various men after dropping out of school years ago to provide for herself and her two younger sisters.
"I have no expectations in life. All I want to do is look after my daughter (who is HIV-negative) but death is imminent... And is what I am waiting for," said the girl, who spoke on condition of anonymity because of her age and to avoid stigma in her community.
Road accidents and injury are the number one killer of adolescents globally, said Michael Hollingdale, a UNAIDS spokesman.
About 120,000 people aged between 10-19 years died of AIDS-related illnesses in 2013, the eight international organizations said while launching a global campaign in Kenya to stem the spread among adolescents.
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Adolescent girls, particularly in sub-Saharan Africa, are most affected, said the organizations which included UNAIDs, UN children's fund, World Health Organization and the US President's Emergency Plan for AIDS Relief or PEPFAR, among others.
Social-economic factors that see girls having sex at younger ages than their male peers also play a major role, she said. They might date older men who can provide for them, she said.
Others, such as the 16-year-old, are forced to fend for themselves at young ages and become victims of sexual exploitation, abuse and rape, Dr. Otiso said.
The global campaign, called "All In" will seek to address the imbalance by encouraging strategic changes in policy and involving more young people in the effort, the organisations said.