Climate change and emerging infectious diseases: a growing global risk
Summary
Climate change is reshaping the global landscape of infectious diseases. From heatwaves that accelerate mosquito-borne outbreaks to shifting wildlife ranges that increase zoonotic spillover risks, scientific evidence now firmly links climatic changes to the rise and spread of human pathogens. This article explores the latest research on how rising temperatures, extreme weather events, and ecological disruption are fuelling emerging disease threats — and outlines why urgent, coordinated climate action is critical for protecting global health.
Climate change is increasingly recognised as a key driver of emerging infectious disease risk. The past decade has seen an acceleration in scientific evidence and real-world examples linking climatic shifts to the spread, emergence, and resurgence of human infectious diseases worldwide. From vector-borne illnesses expanding into new regions to ancient pathogens re-emerging from thawing permafrost, climate-related disruptions are altering the global epidemiological landscape.
Introduction
A 2022 study published in
Nature Climate Change found that over 58% of known human pathogenic diseases have been exacerbated by climate hazards such as warming, floods, and droughts. Similarly, the
IPCC Sixth Assessment Report states with very high confidence that climate change has already increased the burden of climate-sensitive infectious diseases, including those transmitted via water, food, and vectors.
Mechanisms linking climate change to emerging infectious diseases
1. Shifts in temperature and precipitation patterns
Rising global temperatures and altered rainfall patterns influence the distribution, abundance, and seasonality of disease vectors such as mosquitoes, ticks, and midges (
source). Warmer climates accelerate the development of viruses or parasites inside insects like mosquitoes or ticks — so the insects become infectious more quickly, and can spread disease more efficiently (source:
Nature). In North America, warming has facilitated the northward expansion of
Ixodes scapularis, the primary vector for Lyme disease, while in Europe,
Ixodes ricinus is appearing at higher altitudes and latitudes (soource:
ECDC).
2. Increased frequency of extreme weather events
Floods, droughts, and cyclones are linked to the contamination of water supplies, disruption of sanitation systems, and increased human-vector contact. For example, the
World Health Organization reported that the global surge in cholera outbreaks in 2022–23 was driven by climate extremes including floods in Pakistan and tropical cyclones in Malawi. Droughts may also facilitate rodent-borne disease transmission by forcing animals into human settlements, as seen in past hantavirus outbreaks (
source).
3. Wildlife range shifts and cross-species transmission
As species relocate in response to climatic stress, new opportunities arise for interspecies viral sharing. A
2022 study in projected that as mammals shift their habitats due to climate change, they could share viruses more than 4,000 times by 2070 — especially among bats — raising the risk that some of these viruses could jump to humans. These shifts have already facilitated the spread of diseases such as West Nile virus into new ecological zones via migratory birds and
Culex mosquitoes (
source).
4. Thawing permafrost and revival of dormant pathogens
Permafrost thaw in the Arctic poses a unique risk of releasing ancient pathogens. In 2016, a heatwave in Siberia thawed frozen soil containing
Bacillus anthracis spores, leading to an anthrax outbreak that killed over 2,000 reindeer and sickened several humans. This event is widely considered a
climate-driven re-emergence of a previously dormant pathogen. The UN Environment Programme has since warned of the potential for permafrost to harbour other microbial threats (source:
UNEP).
5. Population displacement and strained health systems
Climate-induced displacement, urbanisation, and pressure on health infrastructure contribute to increased vulnerability to infectious disease outbreaks. Crowded, resource-limited settings can facilitate the spread of respiratory and water-borne diseases, while extreme weather events may disrupt vaccination campaigns and surveillance systems (source:
WHO).
Recent examples of climate-linked disease outbreaks
Several disease outbreaks over the past decade illustrate how climate variability is shaping infectious disease emergence and transmission patterns.
The
2015–2016 Zika virus epidemic in Latin America coincided with a strong El Niño event and anomalously high regional temperatures. These conditions enhanced the ecological suitability for
Aedes aegypti, the mosquito vector of Zika virus. Elevated temperatures accelerated mosquito development and viral replication, significantly contributing to the scale and speed of the outbreak, particularly in
Brazil.
In 2018, Europe reported its largest recorded
outbreak of West Nile virus, with over 2,000 human cases across Italy, Greece, Serbia, and Romania. The outbreak followed a spring of intense rainfall, followed by a hot, dry summer. This combination created ideal breeding conditions for
Culex mosquitoes and amplified viral transmission in bird populations. Studies have linked this outbreak directly to climate anomalies consistent with long-term regional warming trends.
The
2022–2023 global resurgence of cholera underscores the role of climate extremes in disease dynamics. According to the WHO, 44 countries reported outbreaks, many in regions affected by tropical cyclones, floods, and droughts. In Malawi, for example, Cyclone Freddy overwhelmed water and sanitation systems, precipitating one of the country’s worst cholera outbreaks on record. Similar trends were observed in Pakistan following catastrophic monsoon flooding.
Implications for human and animal health
Climate-sensitive diseases affect both human and animal populations, often through interconnected mechanisms. For instance, biodiversity loss and habitat shifts, increase human-wildlife contact, elevating the risk of zoonotic spillover.
Avian malaria has been spreading into higher elevation zones in Hawaii, threatening native bird populations as rising temperatures allow mosquitoes to survive at altitudes previously too cold for them.
Conclusion
There is now scientific consensus that climate change is amplifying the risk, distribution, and emergence of infectious diseases worldwide: climate-sensitive health threats will become increasingly common without urgent action.
While adaptation strategies such as improved surveillance, vector control, and early warning systems are critical, the sheer scale and complexity of climate-disease interactions mean that mitigating climate change remains the most effective long-term public health intervention.