The pandemic of HIV/Aids, and the poverty associated with it, is hitting children with a force no one foresaw, according to a new study. In Africa, in particular, it has already undone the achievements in social development of the last half century. Life expectancy has fallen by between 18 and 23 years in the worst affected countries; malnutrition has risen; immunisation rates have dropped; more than 13 million children have been orphaned by Aids, 95% of them in Africa; and four million children have died of Aids since the epidemic began. "These are shameful statistics for a world possessing such extraordinary wealth, knowledge and technological capacity," says the study, prepared by Unicef for this week's United Nations Special Session on Children.