ESCMID 2024: The infectious consequences of climate change

Dengue fever is now found in over 120 countries compared to just nine that experienced severe epidemics in the 1970s, given the spread of infectious diseases due to climate change.

Rising temperatures across the globe have exacerbated the risk of infectious diseases with mosquito-borne diseases being detected in more countries than previously noted. Credit: Shutterstock / Jelena Stanojkovic

At the 34th European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Global (formerly ECCMID) conference in Barcelona, Spain, the implications that climate change has on infectious diseases was discussed. 

According to the World Health Organization (WHO), climate change is one of the biggest threats to public health in the 21st century. The direct effects of climate change include increasing global temperatures and extreme weather events, but the long-term impacts include food and water shortages, as well as the exacerbation and emergence of infectious diseases. As changes in temperature, rainfall, and sea levels occur, this is causing contamination of crops, food scarcity, water scarcity, and changes in the growth, survival, and virulence of pathogens. 

One such example can be seen in the Arctic, where temperatures are warming up at a rate that is twice as fast as the rest of the Northern Hemisphere. This is causing the permafrost to thaw and leading to sinking areas of land, holes forming within the ground, methane explosions, and the recirculation of billions of environmental microbes. This was evidenced in the 2016 anthrax outbreaks among reindeer herds in Russia. Today, researchers are working to understand further risks presented by the thawing permafrost by examining samples obtained from horizontal coring. Researchers are using antibiotic adapted Acanthamoeba cultures in their examination of permafrost samples to identify cell lysis caused by viruses. Metagenomic analyses of the isolated viruses have identified potentially animal-infecting viruses such as iridoviruses, asfarviruses, and poxviruses. Although there is no immediate hazard presented to humans at this time, the risk does increase as the Arctic continues to thaw.

Perhaps the most concerning issue related to the impact of climate change on infectious diseases is the potential for this to escalate antimicrobial resistance (AMR).

Another example of the exacerbation and emergence of infectious diseases due to climate change is evidenced from the spread of mosquito-borne diseases. In the 1970s, nine countries were experiencing severe epidemics of Dengue fever. Today, this has increased to over 120 countries, with the disease spreading beyond tropical and sub-tropical regions. These outbreaks are partially due to both periods of heavy rainfall, in which there is an increase of standing water, and drought, in which populations may rely on improperly stored water reserves. 

Perhaps the most concerning issue related to the impact of climate change on infectious diseases is the potential for this to escalate antimicrobial resistance (AMR). As temperatures increase due to climate change, pathogens have the capability to spread to regions of the globe where they were not previously found. This increase in the incidence and prevalence of infectious diseases includes such pathogens as Campylobacter spp., Salmonella spp., Vibrio cholerae, Candida auris, and Plasmodium falciparum, among others. This results in an increased use of antimicrobials, and subsequently, selection pressure, thereby leading to an escalation of AMR. 

Despite the overwhelming amount of evidence connecting climate change and infectious disease consequences, mitigation strategies can be employed. One such initiative is Harmonize, a program coordinated by the Global Health Resilience Team of the Earth Sciences Department at the Barcelona Supercomputing Center-Centro Nacional de Supercomputación (BSC-CNS). The project is working to develop digital toolkits that will allow researchers and practitioners to have the tools and infrastructure to use integrated health, climate, socioeconomic, and environmental data to monitor infectious disease risks. 

Furthermore, the risk of AMR due to climate change can be mitigated by utilising a One Health approach—a program that aims to unify and balance the health of people, animals, and the environment. Overall, researchers agree that the infectious consequences of climate change will require a multidisciplinary approach to enact measurable changes.