The World Health Organization says it is searching for the origin of a mystery illness that has struck more than 370 people in Angola.
Symptoms include extreme drowsiness and loss of muscle control, the United Nations agency says in a report on its Web site. The symptoms are most extreme in children, the report says.
Most patients recover over several days, but many are unable to walk without assistance.
WHO officials said a toxicological cause is suspected, but tests on patients for 300 organic solvents and 800 compounds were negative. Tests for toxic metals such as cadmium, lead, manganese and mercury have shown levels within the normal range.
Health officials are still waiting for results of environmental samples and tests of food and drinking water in Cacuaco in the suburbs of the capital, Luanda, where the outbreak was first reported last month.
WHO officials said they fear the number of people affected by the disease may be greater than reported because some infected would prefer to visit traditional healers or remain at home rather than go to a hospital.
Copyright 2007 by United Press International
Explore further: Restrictions lifted at British bird flu farm