Bacterial meningitis in Malawian adults, adolescents, and children during the era of antiretroviral scale-up and Haemophilus influenzae type b vaccination, 2000-2012

Abstract

Background: We documented bacterial meningitis trends among adults and children presenting to a large teaching hospital in Malawi during introduction of Haemophilus influenzae type b (Hib) vaccination and the rollout of antiretroviral therapy (ART).

Methods: We analyzed data from 51 000 consecutive cerebrospinal fluid (CSF) samples obtained from adults, adolescents, and children with suspected meningitis admitted to the Queen Elizabeth Central Hospital, Blantyre, Malawi, between 2000 and 2012.

Results: There was a significant decline in the total number of CSF isolates over 12 years (incident rate ratio [IRR], 0.93; 95% CI, .92-.94; P < .001). This decline was entirely in children aged <5 years (IRR, 0.87; 95% CI, .85-.88; P < .001) and coincided with the introduction of Hib vaccination. The number of adult isolates has remained unchanged (IRR, 0.99; 95% CI, .97-1.0; P = .135) despite rapid scale-up of ART provision. In children aged <5 years, Streptococcus pneumoniae, nontyphoidal salmonellae (NTS), and Hib were the most frequently isolated pathogens, and have declined over this time period. Streptococcus pneumoniae was the most frequently isolated pathogen in older children and adults. Estimated incidence of bacterial meningitis in 2012 was 20 per 100,000 cases in children aged <14 years, 6 per 100,000 adolescents, and 10 per 100,000 adults.

Conclusions: Rates of bacterial meningitis have declined in children, but not adults, coinciding with the introduction of Hib vaccination. The highly successful rollout of ART has not yet resulted in a reduction in the incidence in adults where the burden remains high. Long-term surveillance of bacterial meningitis outside of the epidemic "meningitis belt" in Africa is essential.

Keywords: Africa; HIV; antiretroviral therapy; meningitis; vaccination.

Figure 1.

Trends in culture positive isolates over time. A, Total numbers of culture-positive cases of bacterial meningitis, 2000–2012, by year. Isolates are subdivided into adults aged >20 years and children and adolescents aged <20 years, compared with all cerebrospinal fluid samples received by the laboratory for analysis (right scale). B, Total numbers of culture-positive isolates by year and pathogen in all children and adolescents aged <20 years of Streptococcus pneumoniae, nontyphoidal salmonellae (NTS), and Haemophillus influenzae (Hib) meningitis. C, Total numbers of culture-positive isolates by year and pathogen in age-known Expanded Program on Immunization vaccine-eligible children aged ≥3 months to <5 years of S. pneumoniae, NTS, and Hib meningitis. Abbreviations: CSF, cerebrospinal fluid; Hib, Haemophilus influenzae; PCV13, 13-valent pneumococcal conjugate vaccine.

Figure 2.

Incidence of culture-positive bacterial meningitis per 100 000 population. A, Incidence and all cases of bacterial meningitis, 2000–2012, in all cases and children and adolescents aged <20 years. B, Incidence and cases by specific age group (only children for whom age was known are included).

Figure 3.

Cumulative numbers of adults and children alive on antiretroviral therapy (ART) per year in the Southern Region of Malawi.

Figure 4.

Seasonality plot of all meningitis cases caused by Streptococcus pneumoniae (A) and nontyphoidal salmonellae (NTS) (B). A, Seasonality of S. pneumoniae. B, Seasonality of NTS.