Incidence, Carriage and Case-Carrier Ratios for Meningococcal Meningitis in the African Meningitis Belt: A Systematic Review and Meta-Analysis

Abstract

BackgroundTo facilitate the interpretation of meningococcal meningitis epidemiology in the “African meningitis belt”, we aimed at obtaining serogroup-specific pooled estimates of incidence, carriage and case-carrier ratios for meningococcal meningitis in the African meningitis belt and describe their variations across the endemic, hyperendemic and epidemic context.MethodsWe conducted a systematic review and meta-analysis of studies reporting serogroup-specific meningococcal meningitis monthly incidence and carriage in the same population and time period. Epidemiological contexts were defined as endemic (wet season, no epidemic), hyperendemic (dry season, no epidemic), and epidemic (dry season, epidemic).FindingsEight studies reporting a total of eighty pairs of serogroup-specific meningococcal meningitis incidence and carriage estimates were included in this review. For serogroup A, changes associated with the transition from endemic to hyperendemic incidence and from hyperendemic to epidemic incidence were 15-fold and 120-fold respectively. Changes in carriage prevalence associated with both transitions were 1-fold and 30-fold respectively. For serogroup W and X, the transition from endemic to hyperendemic incidence involved a 4-fold and 1•1-fold increase respectively. Increases in carriage prevalence for the later transition were 7-fold and 1•7-fold respectively. No data were available for the hyperendemic-epidemic transition for these serogroups. Our findings suggested that the regular seasonal variation in serogroup A meningococcal meningitis incidence between the rainy and the dry season could be mainly driven by seasonal change in the ratio of clinical cases to subclinical infections. In contrast appearance of epidemic incidences is related to a substantial increase in transmission and colonisation and to lesser extent with changes in the case-carrier ratio.ConclusionSeasonal change in the rate of progression to disease given carriage together with variations in frequency of carriage transmission should be considered in models attempting to capture the epidemiology of meningococcal meningitis and mainly to predict meningitis epidemics in the African meningitis belt.

Evaluation of response strategies against epidemics due to Neisseria meningitidis C in Niger

“…These epidemiogenic factors are likely more present at the border of Nigeria and along the Niger River which Nigerian (Niger) part is used to join Nigeria and Mali. As previously hypothesized by Mueller and Gessner , such a factor could be responsible for the surge in carriage prevalence observed during localised epidemics , and micro‐epidemics of viral respiratory infections could be involved. Epidemics were more frequent on the border with Nigeria, and the region of Dosso was the first affected by the outbreak in Niger.…”

The association between respiratory tract infection incidence and localised meningitis epidemics: an analysis of high-resolution surveillance data from Burkina Faso

“…The biological effect could be emphasized by behavioural changes induced by respiratory infections, such as sneezing and coughing, which can further facilitate meningococcal transmission. At the population level, such accelerated transmission is supported by the over10 times increase in meningococcal carriage prevalence during epidemic situations, as observed by most studies during meningitis epidemics 11 , 20 . According to the hypothetical model cited above 1 , the surge in transmission causes the epidemic increase in meningitis incidence, mediated by a high case-carrier ratio during the dry season 11 .…”

“…A hypothetical explanatory model proposed that a viral respiratory infection epidemic in a given population may act as an epidemic co-factor 1 , by rapidly increasing meningococcal transmission and acquisition in the nasopharynx. This would lead to a proportional increase in disease, on the background of high risk of invasive disease given carriage during the dry season 11 . If this hypothesis was correct, routine surveillance data of meningitis-belt countries would show an association between episodes of high incidence rates of acute respiratory infection and the occurrence of localised meningitis epidemics during the dry season.…”

First statewide meningococcal B vaccine program in infants, children and adolescents: evidence for implementation in South Australia

“…It is unclear why MenB rates are higher in SA, why adolescents have a greater disease burden and why the New Zealand strain dominates compared with other states. Host, pathogen and/or environmental factors are likely to contribute and may relate to specific virulence factors of the predominating genotype or population elements such as a dry dusty climate, lower interstate mobility and proportionately lower international visitors than many other states…”