Johannesburg - The United States on Monday announced $127m in aid for southern African countries where the worst drought in decades is affecting millions of people, stunting children and tempting some farmers to eat their grains instead of saving them as seed for the next crop.The region's most severe drought in 35 years is also a growing health crisis. One-third of the world's HIV-infected population lives in southern Africa, and the United Nations says people cannot take their treatment on an empty stomach.In Zimbabwe, once a food exporter to its neighbours and now gripped by an economic crisis, some have been selling their cattle for as low as $50, explaining that the animals are bound to die anyway.In Mbire district, some farmers survive on cassava roots and struggle to dig out drinking water from dry riverbeds."Three or four months to come, if nothing is taken as an assistance then surely it means people are going to die," said farmer Mafios Ganyari. "You will hear the stories of dying here and there."The Southern African Development Community seeks more than $2 billion in aid for drought-hit member states.The UN's World Food Program says the El Nino-induced drought has devastated crops. It has declared southern Africa its highest-level emergency and says 18 million people need urgent food assistance in seven countries: Lesotho, Madagascar, Malawi, Mozambique, Swaziland, Zambia and Zimbabwe.The number of people at risk could grow sharply during the traditional lean season that starts in October, the UN says.The drought has been especially hard on children. Some leave school to seek work, and others are forced into early marriages, according to a report this month by the UN children's agency, World Vision and Plan International.