A predictable comeback: the second pandemic of infections caused by Neisseria meningitidis serogroup A subgroup III in Africa, 1995.

Between 14 January and 4 April 1995 we isolated and characterized 44 meningococcal strains in Cameroon, Chad, Niger, and Burkina Faso; among these was the strain A:4:P1.9/clone III-1, which was involved in the second meningitis pandemic. This isolate was found in the clonal form in Niger and strains of the ET-37 complex were also found in the other three study countries, but apparently did not cause epidemics. One strain (Y:2a:P1.2,5 (ET-37 complex)) was isolated in January 1995 and another (A:4:P1.9) in March 1995 in Garoua (Cameroon). Eight strains were isolated in Moundou (Chad) between January and April 1995: the A:4:P1.9/clone III-1 (1 strain); members of the ET-37 complex (Y:2a:P1.2,5 (4 strains), Y:NT:P1.2,5 (1 strain), and Y:2a:-(1 strain)); and serogroup X (1 strain). In Niger, 31 strains were isolated between February and April 1995 from different regions. All were A:4:P1.9/clone III-1; between November 1994 and April 1995 there were 23814 cases of meningitis reported of which 2227 resulted in death. Three strains were isolated in Burkina Faso in April 1995: two were Y:2a:P1.2,5 (ET-37 complex) and one was A:4:P1.9/clone III-1. Thus in 1995 the epidemic and invasive strain (A:4:P1.9/clone III-1) responsible for the second pandemic was present in the four countries (Cameroon, Chad, Niger and Burkino Faso) that make up the area frequently affected by such epidemics and where cases are generally reported during the dry season.