The dynamics of measles in sub-Saharan Africa.
Although vaccination has almost eliminated measles in parts of the world, the disease remains a major killer in some high birth rate countries of the Sahel. On the basis of measles dynamics for industrialized countries, high birth rate regions should experience regular annual epidemics. Here, however, we show that measles epidemics in Niger are highly episodic, particularly in the capital Niamey. Models demonstrate that this variability arises from powerful seasonality in transmission-generating high amplitude epidemics-within the chaotic domain of deterministic dynamics. In practice, this leads to frequent stochastic fadeouts, interspersed with irregular, large epidemics. A metapopulation model illustrates how increased vaccine coverage, but still below the local elimination threshold, could lead to increasingly variable major outbreaks in highly seasonally forced contexts. Such erratic dynamics emphasize the importance both of control strategies that address build-up of susceptible individuals and efforts to mitigate the impact of large outbreaks when they occur.
Ferrari
Matthew J
MJ
Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. mferrari@psu.edu
Grais
Rebecca F
RF
Bharti
Nita
N
Conlan
Andrew J K
AJ
Bjørnstad
Ottar N
ON
Wolfson
Lara J
LJ
Guerin
Philippe J
PJ
Djibo
Ali
A
Grenfell
Bryan T
BT
D004196:Disease Outbreaks / Q000517:prevention & control; D006801:Humans; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D008458:Measles Vaccine / Q000008:administration & dosage / Q000276:immunology; D009548:Niger / Q000453:epidemiology; D011891:Rain; D012621:Seasons; D013269:Stochastic Processes; D014611:Vaccination
D008458:Measles Vaccine