The southern African nation of Lesotho has the third highest rate of HIV prevalence in the world.
Each year an estimated 23,000 people die of HIV-related causes, from a population of less than two million.
In countries where HIV prevalence is high, life expectancy at birth has fallen.
In southern Africa, average life expectancy at birth is estimated to have dropped to levels last seen in the 1950s. It is now below 50 years for the region as a whole, 35.2 years for Lesotho.
The groups most affected by HIV are infants and young children, and the 30-50 age group, according to the UNAids 2008 Report on the global Aids epidemic.
In sub-Saharan Africa, nearly 12 million children under 18 years of age have lost one or both parents to HIV. Zimbabwe reports that 24% of its children (ages 0-17) have lost one or both parents to HIV.
HIV/Aids knows no socio-economic boundaries, although in poorer nations, the impact of the disease can be harder to bear for low-income households.
A recent study of eight countries found greater HIV prevalence among adults with higher levels of wealth than among those with the lower income.
The UNAids report suggests this is linked to the fact that wealthier and better educated people tend to have greater sexual autonomy and higher rates of partner change and are more likely to live in cities, where HIV prevalence is generally higher.