Project : Long-term epidemiology of Meningococcal Meningitis in the African belt: dynamics and impact of vaccination

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Hortense Greer
5 years ago
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vaccination Hélène Broutin, PhD Post-doctoral researcher (Supervisor: Dr Mark A.

1 Project : Long-term epidemiology of Meningococcal Meningitis in the African belt: dynamics and impact of vaccination Spatio-temporal dynamics (spread, persistence, periodicity), Comparative approach, impact of vaccination Hélène Broutin, PhD Post-doctoral researcher (Supervisor: Dr Mark A. Miller) Division of International Epidemiology and Population Studies, Fogarty International Center, National Institutes of Health

2 Questions and goals Better mechanistic understanding of the epidemiology of MM during recent decades (emergence, diffusion, persistence) Idea = studying the past (long time series) and comparing dynamics in order to: - detect global patterns vs specialty - understand the impact of vaccination - be able to suggest adapted vaccination strategies - For which population size does the disease persist in time? - Can we identify sources of infection (does a same locality or district constantly suffer first cases of an epidemic?) - Do we observe similar routes of transmission of the disease in all countries? - Do we observe synchrony of epidemics between countries? Do we observe regular waves of cases?

3 Concepts when Ecology meets Epidemiology Metapopulation Ecology => POPULATION SIZE PERSISTENCE Epidemiology Critical Community Size (CCS) IMPACT of VACCINATION? => POPULATION FLUX SPREAD concept cities /villages = POPULATION of POPULATIONS CONNECTED BY MIGRATIONS

4 Concepts when Ecology meets Epidemiology - PERSISTANCE : Critical Community Size (CCS) = the minimal population size below which a disease cannot persist in a susceptible population without external input(s) [Bartlett M.S., 1957; Black F.L., 1966; Anderson R.M. & May R.M., 1991; Grenfell B.T. & Harwood J., 1997] analyses of time-period of disease extinction (period with no new cases in a locality) in relation with the population size - DIFFUSION : concept cities / villages = diseases spread from big cities to villages [Anderson R.M. & May R.M, 1991; Grenfell B.T. & Bolker B.M., 1998] Cases time series analyses between localities

5 Concepts when Ecology meets Epidemiology Population dynamics (Extinction-recolonization concept) extinction risk for the species Species maintain

6 Concepts when Ecology meets Epidemiology Population dynamics and Epidemiology (Periodicities - synchronism) Best control Disease persistence These questions are also highly relevant in a global control perspective

Spatio-temporal dynamics of MM in Africa GLOBAL SCALE - Periodicity / synchrony

Persistence / Diffusion in relation with population size : can we detect sources of

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7 Spatio-temporal dynamics of MM in Africa GLOBAL SCALE - Periodicity / synchrony NATIONAL SCALE (inter-district) LOCAL SCALE (intra district) Sikasso District Mali Persistence / Diffusion in relation with population size : can we detect sources of infection? Not only considered epidemics periods (e.g.1994 and 1996) but also inter-epidemics (i.e to 1996) to make the link between epidemics)

8 Illustrations A) B) Figure extracted from Broutin H, Mantilla-Breniers N. and P. Rohani, Ecology of infectious disease:an example with two vaccine-preventable infectious diseases. Chapt 12 In Encyclopediae of infectious diseases, in press

9 Different steps Data Detailed and long epidemiological time series : Weekly, by district Data analyses - local persistence of the disease in a longterm - local to global diffusion patterns of MM - comparison between countries Genetics data (serotype) Vaccination data - spatial and temporal persistence of serotype in population - periodicity and route of transmission of different serotypes? - quantifying lags between serotypes dynamics - impact of vaccination on these dynamics ALL THESE analyses will allow a BETTER comprehension in order to be able to Model dynamics of the disease

10 Integration of all components Population size Genotype Vaccine status Climate Limits / questions Last of immunity? Proportion of asymptomatic carrier?

11 - Collaboration with Dr MP. Préziosi from the WHO (Vaccine Program Initiative) - Dr Pejman Rohani, University of Georgia, Athens, GA, USA. Availability of detailed data: on MM cases, vaccination and serotype, weekly data, for different countries. Thank you for your attention

MENINGITIS EPIDEMIC TRENDS in AFRICA. Mamoudou H. DJINGAREY, MD/MPH WHO-IST/WEST AFRICA OUAGADOUGOU

MENINGITIS EPIDEMIC TRENDS in AFRICA Mamoudou H. DJINGAREY, MD/MPH WHO-IST/WEST AFRICA OUAGADOUGOU Background Epidemic Meningococcal meningitis = a challenging public health threat in Africa. 1996: Devastating