Climate change has caused a spike in the number of recorded vector-borne diseases like dengue and malaria, a new study has revealed.
The 2022 report ofthe Lancet Countdown on health and climate change: health at the mercy of fossil fuels outlines the impact of climate change on worsening health hazards and extreme weather events, as well as its economic fallout and possible actions for mitigation.
Spread of disease-causing mosquitos
The study finds that changing climate patterns, coupled with other factors like urbanisation and increased movement of people and goods, have boosted the spread of disease-causing mosquitos. The climatic conditions needed for mosquitos to thrive increased by 11.5% and 12% from 1951-60 to 2012-21 for Aedes aegypti and Aedesalbopictus respectively — the species of mosquitos that cause diseases like dengue and chikungunya. The length of the transmission season for malaria also increased by 31.3% in American highlands and by 13.8% in African highlands from 1951–60 to 2012–21, the Lancet report said.
This is not the first time that climate change and increased movement have emerged as the reason for an increased spread of diseases, affecting all forms of life. The European Centre for Disease Prevention and Control states that Aedesalbopictus has undergone a “dramatic global expansion” aided by human activities like the movement of used tyres and ‘lucky bamboo’ plants. Passive transit has spread this mosquito globally.
The 2022 Living Planet Report, released a few weeks ago, said that beetles and moths that attack forests in northern regions, like the temperate and taiga zones of North America and Europe, survive better in warmer climates. These insects kill trees on a mass scale, wiping off certain vegetation from large areas. Many disease-causing insects and worms also survive better in warmer climates and have now moved to once-colder regions of the Arctic and Himalayan highlands.
Around half the population of the world now lives in areas where dengue is present, the Lancet report says. Arthropod-transmitted viruses, or arboviruses, have spread rapidly in the past two decades. Dengue, chikungunya, Zika virus, yellow fever, and Japanese encephalitis are a few common arboviral diseases, and all of these are caused by the bite of an infected mosquito.
Spread of dengue
The basic reproduction number (R0) for the transmission of dengue increased by 11·5% for Aedes aegypti and 12% for Aedes albopictus on average during 2012–21.
Change in climate suitability for infectious diseases. (Thin lines show the annual change. Thick lines show the trend since 1951.) | Photo Credit: The Lancet Report
The length of the transmission season increased by approximately 6% for all arboviruses in the same time period.
Healthcare
As per the Lancet report, healthcare access and quality, and the proportion of population in urban environments are the two main determinants of dengue vulnerability.
Timely medical intervention is the key to preventing severe dengue outbreaks. Between 1990 and 2019, both low and medium Human Development Index (HDI) countries recorded improvements in the vulnerability to dengue due to improvements in healthcare. Low HDI countries saw a 43% reduction in vulnerability to severe dengue outcomes while medium HDI countries saw a 23% reduction, due to better healthcare services. High HDI countries, however, did not follow this trend. In fact, vulnerability to dengue in very high HDI countries increased by 5%, and urbanisation is believed to be the factor driving the spike.
“Saving lives in the face of the climate crisis requires urgent, just, and radical action. The humanitarian sector must deliver flexible responses, embedding high levels of uncertainty into their operating environments, and working to reduce their own environmental footprints,” Lousia Baxter of Médecins Sans Frontières said in a recent comment published by the Lancet.
- The Lancet report finds that changing climate patterns, coupled with other factors like urbanisation and increased movement of people and goods, have boosted the spread of disease-causing mosquitos.
- The climatic conditions needed for mosquitos to thrive increased by 11.5% and 12% from 1951-60 to 2012-21 for Aedes aegypti and Aedesalbopictus respectively
- As per the study, healthcare access and quality, and the proportion of population in urban environments are the two main determinants of dengue vulnerability.
