Serogroup X meningococci (NmX) historically have caused sporadic and clustered meningitis cases in sub-Saharan Africa. To study recent NmX epidemiology, we analyzed data from population-based, sentinel and passive surveillance, and outbreak investigations of bacterial meningitis in Togo and Burkina Faso during 2006–2010. Cerebrospinal fluid specimens were analyzed by PCR. In Togo during 2006–2009, NmX accounted for 16% of the 702 confirmed bacterial meningitis cases. Kozah district experienced an NmX outbreak in March 2007 with an NmX seasonal cumulative incidence of 33/100,000. In Burkina Faso during 2007–2010, NmX accounted for 7% of the 778 confirmed bacterial meningitis cases, with an increase from 2009 to 2010 (4% to 35% of all confirmed cases, respectively). In 2010, NmX epidemics occurred in northern and central regions of Burkina Faso; the highest district cumulative incidence of NmX was estimated as 130/100,000 during March–April. Although limited to a few districts, we have documented NmX meningitis epidemics occurring with a seasonal incidence previously only reported in the meningitis belt for NmW135 and NmA, which argues for development of an NmX vaccine.
For unknown reasons, serogroup W135 achieved epidemic status, primarily among young children, and then largely disappeared over a short time period. The continued circulation of multiple strains with epidemic potential emphasizes the need for ongoing surveillance and the potential benefit of vaccines that are protective across serogroups.
Streptococcus pneumoniae causes a substantial proportion of meningitis cases in the African meningitis belt; however, few reports exist to quantify its burden and characteristics. We conducted population-based and sentinel hospital surveillance of acute bacterial meningitis among persons of all ages in Burkina Faso and Togo in 2002-2006. S. pneumoniae and other organisms were identified by culture, polymerase chain reaction, or detection of antigen in cerebrospinal fluid (CSF). Information was collected on 2843 patients with suspected acute bacterial meningitis. CSF specimens were collected from 2689 (95%) of the patients; of these 2689, 463 (17%) had S. pneumoniae identified, 234 (9%) had Haemophilus influenzae type b identified, and 400 (15%) had Neisseria meningitidis identified. Of the 463 cases of S. pneumoniae meningitis, 99 (21%) were aged <1 year, 71 (15%) were aged 1-4 years, 95 (21%) were aged 5-14 years, and 189 (41%) were aged >or=15 years (age was unknown for 9 [2%]). In Burkina Faso, the annual incidence rate of pneumococcal meningitis was 14 cases per 100,000 persons, with annual incidence rates of 77, 33, 10, and 11 cases per 100,000 persons aged <1 year, <5 years, 5-14 years, and >or=15 years, respectively. The case-fatality ratio for S. pneumoniae meningitis was 47% (range for age groups, 44%-52%), and 53% of deaths occurred among those aged >5 years. S. pneumoniae meningitis had an epidemic pattern similar to that of N. meningitidis meningitis. Of 48 isolates tested for serotype, 18 were from children aged <5 years; of these 18, 3 isolates (17%) each were serotypes 1, 2, and 5, and 5 isolates (28%) were serotype 6A. The 7-, 10-, and 13-valent pneumococcal conjugate vaccines would cover 6%, 39%, and 67% of serotypes identified among children aged <5 years, respectively. Of the 30 serotypes identified for patients aged >or=5 years, 18 (60%) were serotype 1, whereas no other serotype constituted >10%. The 7-, 10-, and 13-valent vaccines would cover 7%, 70%, and 77% of serotypes. Epidemic pneumococcal meningitis in the African meningitis belt countries of Burkina Faso and Togo is common, affects all age groups, and is highly lethal. On the basis of a modest number of isolates from a limited area that includes only meningitis cases, 7-valent pneumococcal conjugate vaccine might have only a limited and short-term role. By contrast, the proposed 10- and 13-valent vaccines would cover most of the identified serotypes. To better inform vaccine policy, continued and expanded surveillance is essential to document serotypes associated with pneumonia, changes in serotype distribution across time, and the impact of vaccine after vaccine introduction.
BackgroundThe development of optimal vaccination strategies for pneumococcal conjugate vaccines requires serotype-specific data on disease incidence and carriage prevalence. This information is lacking for the African meningitis belt.MethodsWe conducted hospital-based surveillance of acute bacterial meningitis in an urban and rural population of Burkina Faso during 2007–09. Cerebrospinal fluid was evaluated by polymerase chain reaction for species and serotype. In 2008, nasopharyngeal swabs were obtained from a representative population sample (1 month to 39 years; N = 519) and additional oropharyngeal swabs from 145 participants. Swabs were evaluated by culture.ResultsAnnual pneumococcal meningitis incidence rates were highest among <6-month-old (58/100,000) and 15- to 19-year-old persons (15/100,000). Annual serotype 1 incidence was around 5/100,000 in all age groups. Pneumococcal carriage prevalence in nasopharyngeal swabs was 63% among <5-year-old children and 22% among ≥5-year-old persons, but adding oropharyngeal to nasopharyngeal swabs increased the estimated carriage prevalence by 60%. Serotype 1 showed high propensity for invasive disease, particularly among persons aged ≥5 years.ConclusionsSerotype 1 causes the majority of cases with a relatively constant age-specific incidence. Pneumococcal carriage is common in all age groups including adults. Vaccination programs in this region may need to include older target age groups for optimal impact on disease burden.
Summaryobjectives To evaluate risk factors for meningococcal carriage and carriage acquisition in the African meningitis belt, comparing epidemic serogroup A (NmA) to non-epidemic serogroups.methods During the non-epidemic meningitis season of 2003, pharyngeal swabs were taken at five monthly visits in a representative population sample (N = 488) of Bobo-Dioulasso, Burkina Faso (age 4-29 years) and analysed by culture. Standardized questionnaires were administered. In 2006, a similar study was performed in 624 individuals (age 1-39 years) during an NmA meningitis epidemic. We evaluated serogroup-specific risk factors for carriage, carriage acquisition and clearance using multivariate logistic and Poisson regression, and a Cox proportional hazard model.results The prevalence of NmA carriage (current or recent pharyngitis or rhinitis) was 16% (31%) vs. 0% (9%) in the epidemic vs. the hyperendemic setting. During the epidemic situation, NmA carriage was significantly associated with recent sore throat (adjusted odds ratio (OR), 3.41) and current rhinitis (OR 2.65). During the non-epidemic meningitis season in 2003, air humidity (20-39% and ‡40%, compared to <20%) during the month before swabbing was significantly and positively associated with carriage acquisition of non-groupable meningococci (OR 2.18 and 1.55) and inversely with carriage clearance (hazard ratio 0.61 and 0.27, respectively).conclusion Respiratory tract infections may increase meningococcal carriage, and thus contribute to epidemic risk, in addition to seasonality in the meningitis belt. Humid climate may favour carriage of unencapsulated meningococci. These findings may help identifying interventions against epidemic and hyperendemic meningococcal meningitis due to non-vaccine serogroups.
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