How will climate change affect the risk of mosquito borne diseases ? Here are some thoughts - updated
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1) Expansions in the geographical range of malaria transmission are more likely to be altitudinal rather than longitudinal. In Africa, this will likely mean more malaria in highland regions; not necessarily in the Sahel
2) The effects of climate warming will be context specific; and must be evaluated with respect to not just temperatures but also other elements such as humidity, hydrology, precipitation, topography etc
3) Malaria mosquitoes (Anopheles) are generally less likely to survive warmer temperatures than Aedes mosquitoes (which transmit dengue, Chikungunya, zika etc). In Africa, we may end up with less malaria but more dengue and the like
4) Increased frequencies of extreme weather events, especially flooding, not only increase the risk of mosquito-borne diseases, but more importantly disrupt health systems. In places that are nearing elimination, where immunity levels might have been significantly reduced, any small upsurges in malaria cases, amid health system disruptions could lead to unexpectedly high mortality rates in both adults and children.
5) Mosquitoes, like all other organisms, are constantly adapting, so some of the predictions we have today may become [partially] invalid depending on the direction of these adaptations. For example, if malaria vectors become more tolerant to heat (as has been demonstrated in some species), they might be able to sustain disease transmission more widely even under increased climate warming
6) Despite current data suggesting a limited direct impact of climate change on malaria, the risk of indirect effects, especially health system disruptions and reallocation of resources, justifies efforts to eliminate malaria proactively. You don't want to be dealing with malaria outbreaks when there are also climate-induced disasters like floods. So malaria control/elimination can be considered an adaptation strategy against climate change
7) In most locations, changes in land-use and land-cover changes, will have greater, more immediate and more direct impact on disease risk than climate change per se - by the way it is easier to measure land-use/land-cover changes than it is to measure climate change
8) The environment, especially the built environment is changing rapidly in Africa. For instance, the proportion of homes that now have metal roofs as opposed to thatch roofs has more than doubled since 2000. My people are building better homes. For Africa's most notorious malaria vectors, such as Anopheles gambiae and Anopheles funestus, which love human dwellings, this change creates a very different microclimate for their survival. How this will impact disease risk remains to be fully understood, but so far, it appears that it will significantly reduce the risk of malaria
9) Broadly speaking, climate science is tough and requires very long-term plans, dedicated scientists and patience. There are still a ton of questions unanswered, especially with regard to local effects of climate change in different localities