In Botswana, where HIV-prevalence is over 35 per cent, the lifetime risk of dying of Aids for a 15-year-old boy at current infection rates is almost 90 per cent.
The world's fastest-growing epidemic is in Eastern Europe and Central Asia, where injecting drug use is driving infection, especially among young men.
HIV/Aids has started to reverse gains made in child mortality rates, particularly in countries where child mortality due to other causes had been significantly reduced.
In rich countries, the use of antiretroviral drugs combined with elective caesarean delivery and safe infant feeding has reduced mother-to-child transmission to almost zero.
HIV-positive children often die from common childhood illnesses such as chicken pox and measles as their weakened immune systems struggle to respond.
The antibiotic cotrimoxazole gives highly effective protection against these diseases and at just 1.7p a day, could make a real difference to the lives of four million children.
In rich countries, more than 80 per cent of HIV-positive infants are still alive at the age of six and some survive to have children of their own.
Even for the lucky few children that have access to treatment, formulations are rarely packaged for children so they have to break up adult-sized tablets or swallow unpleasant-tasting liquids.
Despite predictions that burgeoning numbers of orphans in sub-Saharan Africa will create insecurity on the continent, a recent study of 40 African countries shows 90 per cent of orphans are cared for within extended families.
The sexual transmission of HIV means that children orphaned by Aids are more likely to lose both parents than children orphaned by other causes.
Children living in households with sick or dying parents are often more vulnerable, disadvantaged and malnourished and less likely to go to school than children that have actually lost their parents.
Orphans are vulnerable to exploitation, abuse and recruitment into exploitative labour, and may resort to exchanging sex for food or basic items to survive.
Adolescents are more likely to practise safe sexual behaviour than adults, but remain vulnerable if they do not know the facts about HIV transmission.
In Swaziland, where HIV-prevalence is approaching 40 per cent, only 27 per cent of girls aged between 15 and 19 years know how to protect themselves from the virus.
About one million children are abducted or coerced into the sex trade each year. In Cambodia, more than a quarter of sex workers aged 15 to 19 are HIV-positive.
This is cache, read story here
