Meningococcus serogroup C clonal complex ST-10217 outbreak in Zamfara State, Northern Nigeria

Abstract

After the successful roll out of MenAfriVac, Nigeria has experienced sequential meningitis outbreaks attributed to meningococcus serogroup C (NmC). Zamfara State in North-western Nigeria recently was at the epicentre of the largest NmC outbreak in the 21^st Century with 7,140 suspected meningitis cases and 553 deaths reported between December 2016 and May 2017. The overall attack rate was 155 per 100,000 population and children 5-14 years accounted for 47% (3,369/7,140) of suspected cases. The case fatality rate (CFR) among children 5-9 years was 10%, double that reported among adults ≥ 30 years (5%). NmC and pneumococcus accounted for 94% (172/184) and 5% (9/184) of the laboratory-confirmed cases, respectively. The sequenced NmC belonged to the ST-10217 clonal complex (CC). All serotyped pneumococci were PCV10 serotypes. The emergence of NmC ST-10217 CC outbreaks threatens the public health gains made by MenAfriVac, which calls for an urgent strategic action against meningitis outbreaks.

Figure 1

Summary of CSF specimen collection and processing in Zamfara State.

Figure 2

The geographical distribution of the meningitis outbreak in Zamfara State. The location of Zamfara state in Nigeria is shown in (A). Suspected cases per 100,000 population (B), laboratory-confirmed cases per 100,000 population (C) and case fatality rates (D) across LGAs are shown by colour gradient. The pie charts represent the pathogens detected in confirmed cases (C).

Figure 3

Epidemiologic curve of the meningitis outbreak in Zamfara State. The attack rates (A), case fatality rates (B) and laboratory-confirmed cases (C) by epidemiologic week. The distribution of pathogens detected among laboratory-confirmed cases is shown in (C).

Figure 4

Case fatality rates and laboratory-confirmed cases by age group in Zamfara State. The case fatality rates and total suspected cases are shown by age group (A). The distribution of pathogens among laboratory-confirmed cases by age-group (B). The suspected case counts by age group are presented in Table 1.