Climate Change; The Influence on Disease


Hi!


As you may have read in our previous post, climate change is having a very real impact on our planet. A crucial topic of concern is the potential impact of our changing climate on disease.


The relationship between the changing environment and disease is complex. There are many factors involved, and the impact of climate change may be very different depending on the disease in question.


For example it may impact the distribution of vectors disease....


Climate change may alter the environmental suitability for a vector, this may lead to vectors migrating to more suitable areas, exposing these areas to disease not previously present.


Research available predicts possible outcomes of our changing climate on disease. One study predicts that climate change will expand and increase the risk of viral transmission by the Aedes aegypti mosquito [1] - an important mosquito involved in disease transmission. Importantly, it also shows patterns differ among the mosquito species, climate pathways, localities and more. Ultimately predicting that new populations may become at risk - Europe included in regions predicted to face increased risk [1].


One disease of concern is Dengue, a virus transmitted by Aedes aegypti mosquitoes. The incidence of dengue has increased significantly over the last 50 years [2]. With increasing temperatures being an important factor in the spread of these mosquitoes [3], the impact of global warming on the distribution of the vector-borne disease is a concern.



Zika also poses a potential threat in the face of our changing environment, with moderate concern of outbreaks in the WHO European region including France, Italy and Malta. These regions have suitable environmental conditions for transmission of the main mosquitoes involved in transmission (Aedes aegypti). They tend to survive in warmer climates, additionally warmer climates can allow for the parasite to develop quicker inside the vector. In addition to the suitable climate for mosquitos - the high population density and urban settings promote transmission amongst the population [4], highlighting the potential risk these regions face given the predictions of global warming.


Currently Aedes aegypti populations are not found in these regions, however the species Aedes albopictus still pose a threat. Found in 18 countries of the Mediterranean Basin, Aedes albopictus are considered to have a lower ability for transmission of viruses in compared to Aedes aegypti. However, this species is becoming of increasing concern and has been linked with outbreaks of Chikungunya (a viral disease transmitted by mosquitoes) in Italy as recently as 2017 . In addition to other factors, heatwaves have been suggested to be a contributing factor to the 2017 outbreak [5]. This emphasises that constant surveillance and monitoring is crucial in times of increasing temperatures and weather events such as heat waves that may impact the distribution and transmission of disease.




It may also increase risk of disease due to increased extreme weather events...



Extreme weather events are a clear way we see the effects of climate change on disease. As we mentioned in our previous post click here- increased severe weather events are having serious impacts on human health - one example being flooding. The warming climate exacerbates many factors that induce floods, which are seeing increased occurrences in different regions of the world [6]. This can lead to increased risk of disease and disease related deaths. Flooding can lead to contamination of water supplies, leading to pathogens such as bacteria making their way into our water and food sources [6]. Flooding just being one example of how these extreme weather events induced by global warming can impact the health and well being of many.



It can also influence non infectious disease linked to food insecurity


The influence of global warming does not only influence communicable disease. The projected increasing temperatures from climate change will likely lead to increased malnutrition, and severely affect people from low to middle income countries. High temperatures and severe weather events leading to the destruction of crops, reducing the amount of farmable land and also reducing the productivity of livestock all being of huge concern. The reduction in crop yield will affect diet diversity and also reduce the amount of nutrients in crops[7], leading to malnutrition and poor health amongst other issues.


These are just a few examples of how climate change may be able to influence disease - only time will tell the true extent of the impact. Surveillance will be key to prevent/act - only a response to the symptoms of climate change.


In the meantime...

Its crucial the following are in place:

  • Surveillance systems to see early warning signs of infectious disease outbreaks or changes in disease transmission and distribution of disease

  • Strong communication systems in place between regions and countries

  • Investments into health infrastructure particularly in lower resource settings

  • Developing social infrastructure to reduce migration

  • Deploying low cost control methods such as mosquito nets

  • Collaboration across all sectors



Some useful resources for you to learn more !



As always we would love to hear from you so don't hesitate to contact us with questions, topic requests or even feedback on our page !



- L&A


References:



[1]Ryan, S.J., Carlson, C.J., Mordecai, E.A. and Johnson, L.R., 2019. Global expansion and redistribution of Aedes-borne virus transmission risk with climate change. PLoS neglected tropical diseases, 13(3), p.e0007213. https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007213#sec006


[2] Ebi, K.L. and Nealon, J., 2016. Dengue in a changing climate. Environmental research, 151, pp.115-123. https://www.sciencedirect.com/science/article/pii/S0013935116303127#bib36


[3] Murray, N.E.A., Quam, M.B. and Wilder-Smith, A., 2013. Epidemiology of dengue: past, present and future prospects. Clinical epidemiology, 5, p.299.


[4] Blagrove, M., Caminade, C., Diggle, P., Patterson, E., Sherlock, K., Chapman, G., Hesson, J., Metelmann, S., McCall, P., Lycett, G., Medlock, J., Hughes, G., della Torre, A. and Baylis, M., 2020. Potential for Zika virus transmission by mosquitoes in temperate climates. Proceedings of the Royal Society B: Biological Sciences, 287(1930), p.20200119.


[5] Rezza, G., 2018. Chikungunya is back in Italy: 2007–2017. Journal of travel medicine, 25(1), p.tay004. https://academic.oup.com/jtm/article/25/1/tay004/4967824


[6] Melissa Denchack, 2019. Flooding and Climate Change: Everything You Need to KnowNatural Resource Defence Council https://www.nrdc.org/stories/flooding-and-climate-change-everything-you-need-know


[7]Niles, M., Emery, B., Wiltshire, S., Brown, M., Fisher, B. and Ricketts, T., 2021. Climate impacts associated with reduced diet diversity in children across nineteen countries. Environmental Research Letters, 16(1), p.015010. https://iopscience.iop.org/article/10.1088/1748-9326/abd0ab



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