Only half of those infected in South Africa by HIV - the virus that causes Aids - have access to life-saving medicines and as Claudia Hammond found out, the care for those dying can still fall on children.
The little girl comes into the headmaster's office to meet us and she is smiling, wearing her school uniform of shiny turquoise blue tracksuit bottoms and a white short-sleeved shirt.
She looks about nine or 10, but that is the consequence of malnutrition during her time growing up in the shanty town of Lower Crossroads in Cape Town. In fact she is 14.
Zenthu lives in a shack where she sleeps in the same room as her father and adult older brothers. She says that they are often drunk and sometimes there is no food for the family in the evenings.
The moment I ask her about her mother she bursts into tears, sobbing and sobbing.
We stop recording and try to comfort her, not easy when you don't speak the same language and have to talk via the school secretary's translations.
Then very fast and without stopping she is determined to tell us her story.
Her mother gave birth to her baby sister two years ago, but months later still looked pregnant.
A traditional healer said her swollen body was the result of an evil spell cast on her by people who were jealous.
Doctors told her she had excess fluid around her heart, but soon stopped treating her, saying there was nothing more they could do.
Despite the presence of other adults in the household, the care for both the new baby and her dying mother fell to Zenthu, then just 12 years old.
She began skipping school to tend to her mother.
Eventually, in Zenthu's words her mother "succumbed to the excruciating pains".
She had died from HIV/Aids. One in three pregnant mothers in some townships has the virus - so everyone must surely know someone with HIV. But the stigma means it is not discussed.
The walls of the primary school are daubed with red paint saying "HIV kills! Always wear a condom or die!"
Children are bombarded with information, yet to admit to having the virus is different.
It is important to keep everything within the family shack, even if it means your child becoming a 24-hour nurse.
Children cannot always rely on relatives to nurse their dying parents
Couple this with the fact that families who have moved from rural areas have lost the community they once knew, and you can see why children like Zenthu are left to nurse their dying parents alone.
We meet the researchers commissioned by the government who are going door-to-door in the township to assess the number of children caring for their sick parents.
This Oxford University run study will be the largest in the world ever conducted into child carers.
They want to know why young carers are more likely to contract HIV themselves.
The children might catch it while tending to parents' personal care without wearing gloves.
Or perhaps once they have been orphaned they are more likely to develop relationships with older men who can give them clothes and mobile phone time, but whose age makes them more likely to have HIV.
Or that without their parents' protection they might be more vulnerable to rape, a crime so common that some mothers living in the townships take their daughters to have long-lasting contraceptive injections at the age of 12 or 13, not because they think they're going to choose to have sex, but because the likelihood they'll be raped is so high.
Their mothers can't protect them from HIV, but they can stop them getting pregnant.
But when it comes to HIV/Aids there are signs that things might be changing.
The previous health minister was nicknamed Dr Beetroot for suggesting that garlic, olive oil and beetroot could cure HIV.
But her replacement, Barbara Hogan, has already spoken out about HIV in scenes unthinkable in South Africa just six months ago.
She was even serenaded outside her home by the Treatment Action Campaign, an organisation which has fought vigorously against the government to make HIV drugs available.
Some of the academics I spoke to believe that the future for children all depends on the new president's choice of health minister. (Elections are being held next month.)
After pouring out her heart to us, Zenthu gets up to go back to her class.
She is clearly still grieving for her mother, but at no time did she complain that it was unfair that she had to care for her or imply that anyone else should have done it.
She wanted to look after her and tells me that she will never forget her mother as long as she lives.
But when I ask what she wants to do when she leaves school, she answers that she wants to help the next generation of children in her position, so that they don't have to do what she did.
From Our Own Correspondent was broadcast on Saturday, 28 March, 2009 at 1130 GMT on BBC Radio 4. Please check the
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