Highly endemic countries, where prevalence is moderate are Cameroon, Central African Republic, Chad, Congo, Cote d'Ivoire, Guinea, Mozambique, Uganda and United Republic of Tanzania.

There have been 3 major epidemics, one between 1896 and 1906, mostly in Uganda and the Congo, one in 1920 in several African countries, and one that began in 1970 and is still in progress. The disease had practically disappeared between 1960 and 1965. After the DDT success, screening and effective surveillance were relaxed, and the disease has reappeared in endemics over the last 30 years. International DDT spraying from aircraft will do nicely.

Vectors like mosquitoes are now being treated transgen-ically so that they do not transmit some given disease. However, it is still too early to announce success in this fascinating area.