1. Spatio-temporal patterns of meningococcal meningitis in Burkina Faso, Mali and Niger and relationships to climate Sylwia Trzaska 1, Pietro Ceccato 1, Judy Omumbo 1, Michael Bell 1, Madeleine Thomson 1, Mamoudou Djingarey 2, Sassan Noazin 3, Isabelle Jeanne 4 1 The International Research Institute for Climate and Society, Columbia,University, Palisades, NY USA 2 Multidisease Surveillance Center, Ouagadougou, Burkina Faso 3 World Health Organization 4 CERMES, Niamey, Niger Meningitis vaccine programme

2. Rationale Identify which environmental factors can be used as predictors to Meningitis outbreaks in order to develop an Early Warning System based on forecast and monitoring products of the environmental factors.

3. Data and Methods Meningitis Original data for Central Sahel collected by WHO incidence weekly, district level Niger - 42 distr., 1986-2005 Mali - 58 distr., 1994-2005 Burkina Faso – 55 distr., 1997-2005 Atmosphere NCEP Reanalysis (surface) Daily aggregated to weekly 1949-present Coarse resolution (2.5x2.5) but global Consistency among variables Dust TOMS/EPTOMS Daily aggregated to weekly 1996-2004 Resolution 1.5x1 Objective definition of spatial and temporal scales for meningitis incidence variability via statistical analyses Investigation of potential large scale atmospheric predictors All countries, 1997-2005

4. Weeks 5-20, standardized 4 classes Meningitis Mean Seasonal Cycle Cluster Analysis Earlier onset and termination of meningitis season in southern districts Northward progression of the epidemic season

5. Environmental Factors E.g. Week 13 Maximum temperature, Specific Humidity, Wind Northaward progression of Meningitis linked to highest temperatures, in the region of convergence between Harmattan and southwesterlies Highest dustiness (not shown) NOT lowest humidity Termination linked to arrival of moister, cooler and cleaner air

6. Environmental Factors E.g. TOMS w 1-20 Northaward progression of Meningitis linked to highest temperatures, in the region of convergence between Harmattan and southwesterlies Highest dustiness (not shown) NOT lowest humidity Termination linked to arrival of moister, cooler and cleaner air

7. Interannual variability Standardized Annual Incidence Anomalies 3 distinctive spatial structures: uniform epidemics, E/W dipole, Center vs E&W High incidence Low incidence Missing data

8. Niger – Interannual Variability, EOF

9. Niger – Interannual Variability, atmosphere

10. Conclusions Seasonal Cycle District Scale - northward progression of the epidemics Links to surface atmospheric conditions - epidemic season coincides with highest Tmax and dust in the low level wind conv. - moves northward with the seasonal cycle - epidemic season terminates when high humidity/low dust air mass reach the region Consistent with previous studies Future: Establish thresholds Interannual variability Can be approached from annual (or peak) cumulative incidence values for each district Differences in control strategies do not hinder spatial features - large scale epidemic/non epidemic years - dipolar structures (E vs W), not related to boundaries Insufficient length of data for establishing robust results Niger: climatic signal – potential for prediction - for epid./non-epid. years: climatic anomalies in equatorial and S Atlantic - for dipolar years: reversed anomalies between N Tropical Atlantic and Central Sahel Future: Further predictability studies

11. Niger District Level Establish thresholds for dust, tmax, wind Interannual variability Niger – 20 years of record