Threshold response of malaria dynamics to warmer temperatures in an East African highland

Background/Question/Methods

The impact of climate change on infectious diseases, particularly those
that are vector-transmitted, is a pressing and still highly debated
question. This work addresses the impact of warmer temperatures on the
population dynamics of malaria in a Kenyan highland for which a monthly
time series of confirmed cases is available from 1970 to 2002. An
epidemiological model that includes both the human host and the mosquito
vector is parametrized using the observed cases in the 1970s, a decade
of low incidence preceding epidemic behavior.
Results/Conclusions
Projections for the number of cases in the following decades are then obtained by numerical simulation of the model with and without the temperature trend.
Comparisons of these predictions show a significant effect of the increase in temperatures, especially for the 1990s. Furthermore, malaria
cases exhibit in the model a highly nonlinear response to warming, with a threshold behavior as temperature crosses a critical value. Despite
the evidence for a large effect of warmer temperatures, predicted cases are on average still smaller than those observed. These findings suggest that
climate change has already played a role in the exacerbation of malaria in this region and that other factors are likely to also be at play.