On the 3rd of November 2024, the One Health Day was celebrated globally. This reminds us that the intersection of health, climate, and resistance demands cohesive, global action, a goal achievable only through a shared commitment to our interconnected world.

Climate overshoot is a reality, carrying significant ecological, health, and socioeconomic consequences. While “climate change” encompasses a range of long-term shifts in temperature, weather patterns, and atmospheric conditions largely driven by human activities, “climate overshoot” refers to temporary but severe breaches of temperature limits that may prompt irreversible environmental damage.

Countries agreed to pursue efforts to limit global warming to below 1.5 - 2°C at the 2015 Paris Climate Agreement. According to the Climate Overshoot Commission, “climate overshoot” refers to crossing the 1.5 °C threshold. One of the less discussed aspects of climate overshoot is its impact on health systems, particularly with respect to antimicrobial resistance. Antimicrobial Resistance (AMR) occurs when bacteria, viruses, fungi, and parasites adapt and become resistant to medications that successfully treat these infections, is a global public health emergency. Climate change and AMR are linked through several mechanisms.

• Agricultural Pressures: Climate impacts on agriculture, such as altered rainfall patterns and drought, may drive a higher reliance on antibiotics to prevent infections in stressed animals, intensifying antibiotic use and resistance. In regions with weak regulatory oversight, this can lead to unchecked AMR spread, impacting local and global health.
• Changing Ecosystems and Disease Vectors: Rising temperatures can broaden the habitat of disease-causing organisms and their carriers, such as ticks and mosquitoes, leading to increased disease exposure. For example, warmer climates can expand the range of vector-borne diseases (such as malaria or dengue), increase respiratory illnesses due to pollution and wildfires, and lead to waterborne disease outbreaks after floods. This expansion of infectious diseases could increase antibiotic usage, consequently hastening the development of antibiotic resistance.
• Human Migration and Overcrowding: Climate overshoot may trigger human migration and displacement due to extreme weather events or sea-level rise, leading to overcrowded living conditions and increased risk of infection. A high population density often coincides with increased antimicrobial use and poor sanitation, both facilitating the spread of AMR.

It is clear that human health is intricately tied to the health of animals and the environment, and the links between climate change, AMR, and health outcomes are undeniable. Ongoing global health initiatives recognise the need for integrated solutions. The Paris Agreement focuses on reducing emissions to maintain global temperatures below critical thresholds. Although primarily aimed at climate mitigation, the agreement also supports climate adaptation strategies to help buffer health systems against the consequences of overshoot scenarios, including AMR. The WHO’s Global Action Plan on AMR highlights a One Health

approach, stressing collaboration across the human, animal, and environmental health sectors. This plan acknowledges that climatic factors play a role in the spread of AMR, particularly in agriculture and other ecosystems. The One Health High-Level Expert Panel (OHHLEP) emphasises the importance of integrated approaches in addressing AMR and climate health impacts. OHHLEP helps governments align climate and AMR strategies by advocating for the One Health approach, fostering health resilience across sectors.

The impact of climate overshoot on AMR highlights the need for unified action. It is important that we need to reinforce policies that bridge health, environment, and

Agriculture by:

• Reducing Antibiotic Pollution: Strengthening regulations regarding antibiotic use in agriculture and promoting clean water access can protect the environment from antibiotic residues, thus slowing the spread of AMR.
• Supporting Sustainable Agriculture: Climate-resilient crops and livestock practices help to reduce the need for antibiotics. Investing in climate-smart agriculture can mitigate climate impact and limit AMR.
• Investing in Climate-Resilient Health Systems: This refers to building health healthcare systems equipped to handle the increased disease burden and health challenges triggered by climate overshoot. Climate changes can lead to increased occurrence of outbreaks. There is a need to deploy improved health data monitoring systems, especially genomic epidemiology for infectious diseases, improve access to healthcare services and institute community-driven preventive strategies (vaccination, health promotion).

Climate change, health, resistant infections, and antimicrobial use are all entwined within our ecosystem. By investing in sustainable climate-smart healthcare practices, One Health policy, and eco-friendly practices in agriculture, we can truly state that we are committed to a future where the health of people, animals, and the planet is protected for generations to come.

Written by ISID Emerging Leader, Abiodun Egwuenu

References

1. IPCC. (2023). Climate Change 2023: Synthesis Report Summary for Policymakers.
2.  World Health Organization. (2015). Global Action Plan on Antimicrobial Resistance.
3. Murray, C. J., Ikuta, K. S., Sharara, F., Swetschinski, L., Aguilar, G. R., Gray, A., & Han, C. (2022). Global burden of bacterial antimicrobial resistance in 2019: A systematic analysis. The Lancet, 399(10325), 629-655.
4. United Nations. (2015). Paris Agreement.