Extreme weather events resulting from climate change, such as heavy rainfall, will likely affect current malaria control programs and could have a “deleterious” effect on human health unless countermeasures are implemented quickly, according to a study published online in the Journal of Infectious Diseases.
Ross Boyce, MD, MSc, of the Division of Infectious Diseases at the University of North Carolina at Chapel Hill, and colleagues examined the Western Ugandan Kasese District prior to and following severe flooding events in May 2013 to evaluate the impact on malaria rates. The researchers compared high and low elevations, areas with and without rivers, and upstream and downstream differences.
Dr Boyce and colleagues explained that extreme flooding boosted an individual’s chance of testing positive for malaria by about 30%.
There were 7596 diagnostic tests for malaria performed during the study, of which 1285 patients had tested positive. The researchers said the greatest relative increase in malaria rates occurred in areas that were upstream.
“The effects of global climate change extend well beyond warming surface temperatures,” Dr Boyce said in an interview with Infectious Disease Advisor. “Clinicians and public health officials must be aware of these effects, such as the increased frequency of severe precipitation events, when considering the impacts of climate change on human health. As our study showed, these events may lead to increased transmission of malaria, not only in endemic areas, but also in areas that were considered relatively protected by geographic features, such as higher elevation.”
During the interview, Dr Boyce highlighted the differences in the intensity of malaria transmission between adjacent villages. “I found this particularly striking because the physical size of the villages is quite small, often only 2 to 3 square kilometers, and you would not expect such differences. However, our results demonstrated significant differences in malaria transmission both before and after the flood. I attribute this to ‘micro-environments’ within each village that affect water drainage and ultimately the suitability for mosquito breeding sites.”
Dr Boyce and colleagues offered several policy changes to combat the increase in transmission. They suggested targeted interventions between the time of flooding and post flooding. In addition, they stated that sustained control efforts are necessary, “as the effects of the flood on malaria transmission may continue for up to one year after the initial event.” Lastly, the researchers highlighted the importance of understanding local environments to combat malaria transmission.
1. Boyce R, Reyes R, Matte M. Severe flooding and malaria transmission in the Western Ugandan highlands: implications for disease control in an era of global climate change. J Infect Dis. 2016;doi:10.1093/infdis/jiw363.