Tropical Health Matters

Heavy rains, flooding and malaria

A changing climate, even a warming climate, does not directly translate into greater malaria transmission.[i] Lafferty and Mordecai explain that we need a need “a greater appreciation for the economic and environmental factors driving infectious diseases,” as these have their own impact on transmission.[ii] Climate change effects occur in parallel to “changes such as land conversion, urbanization, species assemblages, host movement, and demography.” This wider ecological understanding is needed to “predict which diseases are most likely to emerge where, so that public health agencies can best direct limited disease control resources.”

As the WHO framework for malaria elimination stresses, [iii] “Most countries have diverse transmission intensity, and factors such as ecology, immunity, vector behaviour, social factors and health system characteristics influence both the diversity of transmission and the effectiveness of tools, intervention packages and strategies in each locality.” The Framework goes further to encourage strategic planning and interventions appropriate for the diverse settings or strata within a country. What climate change implies is that the nature of malaria transmission in these strata will change as temperature, rainfall, humidity and human response change. Countries not only need to adapt malaria activities to existing strata, but also be alert to changes in transmission and thus changes needed in strategies.

Increased or decreased vector control activities would be one example of changes that are needed in response to climate, vector habitat and transmission changes. “The receptivity of an area (to vector control interventions) is not static but is affected by determinants such as environmental and climate factors.” Case detection will become even more crucial as transmission drops and the success of elimination programs depends on identifying, tracing and responding to remaining cases promptly and accurately.

The landscape for malaria control and elimination is shifting in part because of the success of interventions since the dawn of Roll Bank Malaria in 1998.  As we have shown here, there may also be shifts due to climate change. Of great concern is the shifts that expose new and more vulnerable populations, such as those in the East Africa highlands to the threat of malaria. National Malaria Programs need strong surveillance efforts that monitor disease, vectors and climate, and be ready to respond.

[Excerpted from Africa Health]

[i] World Health Organization. Climate change and health. Fact sheet. Updated July 2017.

http://www.who.int/mediacentre/factsheets/fs266/en/

[ii] Lafferty KD, Mordecai EA. The rise and fall of infectious disease in a warmer world. F1000Research 2016, 5(F1000 Faculty Rev):2040 last updated: 19 AUG 2016. (doi: 10.12688/f1000research.8766.1).

[iii] Global Malaria Program. A framework for malaria elimination. World Health Organization 2017, ISBN 978-92-4-151198-8. http://www.who.int/malaria/publications/atoz/9789241511988/en/

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