THE earth’s rapidly changing climate has profound and far-reaching effects extending well beyond rising temperatures and sea levels. One of the most concerning impacts is the influence that climate change is having on the emergence, spread, and transmission of infectious diseases. Infectious diseases are caused by pathogenic microorganisms such as viruses, bacteria, fungi, and parasites that can spread from person to person or between humans and animals. Many of these diseases are highly sensitive to climatic conditions, and even small changes in temperature, precipitation patterns, humidity levels, and other environmental factors can significantly alter their prevalence and geographic range.
Pakistan is among the countries most vulnerable to the impacts of climate change, including the increased risk of infectious diseases. The country’s diverse climate zones, ranging from arid deserts to glaciated mountains, make it susceptible to various climate-related health threats. Moreover, Pakistan’s agricultural sector, which employs a significant portion of the population, is highly vulnerable to climate change. Changes in temperature and precipitation patterns can impact crop yields, food security, and the livelihoods of farming communities, potentially leading to malnutrition and increased susceptibility to infectious diseases.
One of the most visible impacts of climate change on infectious diseases is the expansion of diseases spread by insects and other vectors. Mosquitoes, ticks, and other disease-carrying organisms thrive in warm and humid environments, and as temperatures rise globally, their habitats are expanding into new regions. Climate change is also exacerbating the burden of vector-borne diseases in Pakistan too. Areas of Pakistan that were previously too cold for mosquitoes to thrive now see an influx of these disease carriers, increasing the risk of malaria, dengue fever, and other mosquito-borne illnesses.
Malaria, a life-threatening disease caused by a parasite transmitted by infected mosquitoes, is a prime example. According to the World Health Organization (WHO) fact sheet of October 2023, between 2030 and 2050, climate change is expected to cause approximately 250,000 additional deaths per year from undernutrition, malaria, diarrhea and heat stress alone. One of the reasons for this increase in malaria cases is the rise in temperatures, where mosquitoes can now survive and reproduce in previously too-cold areas, exposing new populations to the risk of malaria.
Similarly, due to climate change, the geographic range of dengue fever, a viral disease spread by Aedes mosquitoes, is expanding. The WHO estimates that the number of people at risk of contracting dengue has increased dramatically in recent decades, with about half of the world’s population now living in areas where the disease is endemic. Climate change is also influencing the transmission of waterborne and foodborne diseases. Extreme weather events like heavy rainfall and flooding can contaminate water sources with pathogens like cholera, Cryptosporidium, and Giardia. Additionally, warmer temperatures can increase the risk of food poisoning by accelerating the growth of harmful bacteria like Salmonella and E. coli in food products.
In underdeveloped regions, including Pakistan, where access to clean water and proper sanitation is limited, the impact of climate change on waterborne diseases can be particularly severe. For instance, recent flooding events in Pakistan and Bangladesh resulted in widespread outbreaks of diarrheal diseases like cholera and dysentery, affecting hundreds of thousands of people.
Climate change is also altering the dynamics of zoonotic diseases, which are diseases that can be transmitted from animals to humans. As animals’ habitats are disrupted by rising temperatures, droughts, and other environmental changes, they may migrate to new areas, potentially bringing diseases with them and exposing humans to new pathogens. For example, the Nipah virus, a deadly zoonotic disease that can cause severe respiratory illness and encephalitis, has been linked to climate-induced changes in fruit bat migration patterns and feeding behaviour in regions like South Asia.
Addressing the impact of climate change on infectious diseases requires a multifaceted approach that combines adaptation and mitigation strategies. Adaptation involves developing resilient public health systems, improving disease surveillance and early warning systems, and enhancing access to clean water, sanitation, and healthcare services, particularly in vulnerable communities.
Mitigation efforts focus on reducing greenhouse gas emissions and slowing the pace of climate change itself. This can be achieved by adopting renewable energy sources, increasing energy efficiency, promoting sustainable agriculture and land-use practices, and implementing policies that encourage environmentally responsible behaviour. International cooperation and coordination are essential in tackling this global challenge. Organizations like the WHO and the Intergovernmental Panel on Climate Change (IPCC) play crucial roles in raising awareness, guiding policy decisions, and facilitating collaboration among nations to address the health impacts of climate change. Addressing the root causes of climate change and strengthening our ability to respond to emerging disease threats is an environmental imperative and a matter of global health security. By taking decisive action to mitigate and adapt to the impacts of climate change, we can reduce the risk of future disease outbreaks and protect the health and well-being of communities worldwide.
—The writer, Assistant Professor, Institute of Public Health, is based in Lahore.
