GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva 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

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva - 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 ? 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 Better mechanistic understanding of the epidemiology of MM during recent decades (emergence, diffusion, persistence) Questions and goals …

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

- 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] - 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] Concepts when Ecology meets Epidemiology… analyses of time-period of disease extinction (period with no new cases in a locality) in relation with the population size Cases time series analyses between localities

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

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

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva LOCAL–SCALE (intra – district) Persistence / Diffusion in relation with population size : can we detect sources of infection ? GLOBAL –SCALE NATIONAL SCALE (inter-district) - Periodicity / synchrony Mali Sikasso District Spatio-temporal dynamics of MM in Africa Not only considered epidemics periods (e.g.1994 and 1996) but also inter-epidemics (i.e to 1996) to make the link between epidemics)

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva 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

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva Detailed and long epidemiological time series : Weekly, by district Genetics data (serotype) Vaccination data ALL THESE analyses will allow a BETTER comprehension in order to be able to Model dynamics of the disease - local persistence of the disease in a long- term - local to global diffusion patterns of MM - comparison between countries Data - spatial and temporal persistence of serotype in population - periodicity and route of transmission of different serotypes? - quantifying lags between serotypes dynamics Different steps … Data analyses - impact of vaccination on these dynamics

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva Integration of all components … Population size Genotype Vaccine status Climate Limits / questions Last of immunity ? Proportion of asymptomatic carrier?

GEO Meningitis Environmental Risk Consultative Meeting, sept 2007, WHO, Geneva - 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