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
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Spatio-temporal patterns of meningococcal meningitis in Burkina Faso, Mali and Niger and relationships to climate Sylwia Trzaska 1, Pietro Ceccato 1, Judy.
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Spatio-temporal patterns of meningococcal meningitis in Burkina Faso, Mali and Niger
and relationships to climate
Sylwia Trzaska1, Pietro Ceccato1, Judy Omumbo1, Michael Bell1, Madeleine Thomson1, Mamoudou Djingarey2, Sassan Noazin3,
Isabelle Jeanne4
1 The International Research Institute for Climate and Society, Columbia,University, Palisades, NY USA2 Multidisease Surveillance Center, Ouagadougou, Burkina Faso3 World Health Organization4 CERMES, Niamey, Niger
Meningitis vaccine programme
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.
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
AtmosphereNCEP Reanalysis (surface)
• Daily aggregated to weekly• 1949-present • Coarse resolution (2.5x2.5) but global• Consistency among variables
DustTOMS/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
Weeks 5-20, standardized 4 classes
-0.5
0
0.5
1
1.5
2
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Class 1
Class 2
Class 3
Class 4
Meningitis Mean Seasonal Cycle
Cluster Analysis
Earlier onset and termination of meningitis season in southern districts Northward progression of the epidemic season
Environmental Factors
E.g. Week 13 Maximum temperature,Specific Humidity, Wind
-0.5
0
0.5
1
1.5
2
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Class 1
Class 2
Class 3
Class 4
• 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
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
3 distinctive spatial structures: uniform epidemics, E/W dipole, Center vs E&W
High incidence
Low incidence
Missing data
Niger – Interannual Variability, EOF
Niger – Interannual Variability,
atmosphere
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