A breakdown in the school environment in Africa has led to growing number of cases of HIV amongst young girls being caused by teachers, academics believe.
Two thirds of those affected by HIV and Aids in sub-Saharan Africa are women between 15 and 25 years old.
And one of the crucial reasons for this rise is the number of teachers having sex with their pupils, researchers say.
"If you go to any school within the southern African region you will hear the same story from the girls," Zimbabwean academic Pamela Machakanja told BBC World Service's Africa Live! programme.
Ms Machakanja added that the problem went right to the top in many of Africa's schools.
"Most of the perpetrators are head teachers," she said.
"[They] are supposed to maintain peace and tranquillity within the school.
"They are supposed to educated their teachers about good behaviour, role models, and exemplary etiquettes within the school system."
She argued that the problem was a recent phenomenon, and partly as much a consequence of Aids - and the way it had caused a virtual breakdown in society in some areas.
One 19-year-old girl at a school in Lusaka, Zambia - who asked not to be named - said she knew of many teachers who had sex with a number of their pupils.
"Those teachers are not only going out with one girl at the school - they are going out with several other girls," she told Africa Live.
"You might find that they're going out with three or so."
The pupil added that the reasons her classmates had slept with their teachers were varied.
"Sometimes they just say that they just like the teachers," she said.
"Sometimes they want to be getting good grades."
However she added that the girls were not only sleeping with teachers - and that they were leaving themselves open to HIV infection in a number of ways.
Her friends "have been having sex on so many occasions they can't even count," she said.
"Some have been using condoms and some haven't been using them.
"Sometimes they think their boyfriends - the people they are having sex with - might leave them.
"They fear that, and they decide that they should not use condoms."
She added that "sugar daddies" - older men who girls have sex with in return for the promise of expensive gifts - were also a major factor at her school.
"A lot were having sexual relationships with older men - much older men," she said, adding that this would usually be unprotected.
"They go out with older men because they think they give them many of the things that the need, and they don't want to lose that.
Teachers can also play a key role in HIV education
"They like cellphones - and they don't want the bigger ones, they want the small ones.
"So they go out with older men, who they think can afford to give them the cellphones and to top up their cards."
"I think sex education in school is key in solving this problem," said Ghanaian teacher Clara Boateng.
"When we educate the youth - especially in their schools - they will be able to make informed choices, and then they will go down to their communities, educate their parents and other siblings."
She argued also that in fact amongst children who attended to school, cases of HIV were lower than amongst those who did not.
"The youths who are in school are not mostly affected," she said.
"The majority of the people are people who are out of school."
And she added that teachers could help solve the crisis as much as be part of it.
"Teachers are versatile," she said.
"If they are given the mandate to carry out HIV messages, they can do it and do it well."