Six villagers in the Sinfra focus of sleeping sickness in Côte d'Ivoire who in 1995 were asymptomatic and refusing treatment, despite then being serologically and parasitologically positive for trypanosomes, were followed-up, while still refusing treatment, until 2002. In 2002, five of the six cases remained serologically positive but no trypanosomes could be found in any of them by use of the classical parasitological methods. A PCR-based assay, however, revealed that all six had the DNA of Trypanosoma brucei s.l. in their blood, so confirming the low sensitivity of the classical parasitological tests. The analysis of satellite, minisatellite and microsatellite markers indicated that, in 2002, all six cases were infected with a 'new' distinct genetic group of T. brucei s.l. and four were co-infected with T. b. gambiense group 1. The epidemiological consequences of such co-infections are discussed. The 'new' group of T. brucei had a molecular pattern that differed from those of the classical T. b. gambiense group 1 and the 'bouaflé' group.