The United Nations is set to launch a major campaign to help tens of thousands of Ethiopian children facing an outbreak of lethal diseases, from diarrhoea to malaria, after rain showers hit the drought-stricken Oromia region, insufficient to undo the damage of two failed rainy seasons but enough to form shallow pools that breed disease-bearing insects.

Eight mobile health teams, backed by the UN Children's Fund (UNICEF) and equipped with emergency health kits and supplementary food for malnourished children, are fanning out across the worst affected zone of Borena, home to almost 1 million people. UN-backed sanitation teams will be moving in over the next two weeks to persuade communities to burn animal carcasses that are polluting water sources.

"The region has been praying for good rains for two years now. It is a cruel irony that these short and patchy showers are actually raising new fears for the lives of children living along Ethiopia's drought-stricken south-eastern border," the head of UNICEF Ethiopia's Early Warning/Disaster Preparedness and Response section, Marc Rubin, said.

"The good news is that there is still time to make a real difference in the region. We have had an early enough warning. We also have experienced staff on hand who can get to the field and start saving lives. Equally important, funding for our programmes has started to come in from everyone," he added, ranging from the government of Sweden, which last week gave UNICEF $3 million, to a group of California schoolchildren who collected $1,500 from their friends in what he called "an amazing effort."

The agency noted that rainwater is washing through piles of dead animals outside most communities and flowing on to pollute the few remaining water sources. Anyone drinking from such polluted water risks a range of water-borne diseases like diarrhoea - often trivial in the West but potentially fatal among an already weakened pastoralist population with very little access to health facilities.

Child malnutrition levels are still at alarming levels and livestock deaths continue to climb. UNICEF will be partnered by Ethiopia's regional health authorities and non-governmental organizations (NGOs) in the campaign to address the new disease risk.

Some 1.7 million Ethiopians are struggling to survive in a drought that has spread out to affect the whole Horn of Africa, including Kenya, Somalia and Djibouti. More than 56,000 children under the age of five are currently vulnerable to moderate and severe malnutrition across Oromia and Ethiopia's Somali regions. There have already been reports of deaths from measles, diarrhoeal diseases and malnutrition.