Introduction: Climate change, one of the most pressing global issues of our time, is causing profound changes in our environment, including alterations in the distribution and prevalence of disease vectors. Bangladesh, a densely populated and low-lying country in South Asia, is particularly vulnerable to the impacts of climate change. One of the most significant consequences of these changes is the increased prevalence of mosquito-borne diseases. According to the Directorate General of Health Services (DGHS), the death toll from dengue rose to 804 in the country. During the period (Sept, 2023) 2,598 more patients were hospitalized with the viral fever, of the new patients, 881 were admitted to hospitals in Dhaka and the rest outside the capital--indicating a worsening situation across the country. A total of 10,330 dengue patients, including 4,208 in the capital, are now receiving treatment at hospitals across the country. So far, the DGHS has recorded 164,562 dengue cases and 153,428 recoveries this year. In September, the Aedes mosquito-borne Dengue has claimed the lives of 211 people across the country. A total of 40,754 cases were also reported during the same period.

Climate Change and Mosquito-Borne Diseases

Temperature and Mosquito Activity: Temperature plays a pivotal role in the life cycle and behavior of mosquitoes. Warmer temperatures can accelerate mosquito development, shorten the incubation period of pathogens within mosquitoes, and increase mosquito biting rates. In Bangladesh, rising temperatures have created favorable conditions for mosquito breeding and disease transmission. Bangladesh has experienced an average rise in temperature of 0.5°C between 1976 and 2019. This warming trend has contributed to the expansion of mosquito habitats, thereby increasing the risk of mosquito-borne diseases. In the recent time Dengue is likely to increase for Dhaka as the climatic conditions become more suitable. Humidity in the range of 60 to 80 percent, maximum temperature between 25°C and 35°C, and rainfall between 200-800 mm create ideal conditions for mosquitoes. Weather data between 1976 and 2022 indicate Dhaka is experiencing falling humidity levels, rising temperatures, and heavier summer rainfall. These together with factors like urbanization are increasing the risk of the spread of dengue in Dhaka city.

Precipitation and Mosquito Breeding: Changes in precipitation patterns are another significant consequence of climate change. Bangladesh experiences seasonal monsoons, and alterations in these patterns can lead to the creation of stagnant water bodies, ideal breeding grounds for mosquitoes. Increased rainfall and the subsequent formation of puddles and ponds provide opportunities for mosquito larvae to thrive. The data indicates that Bangladesh has observed increased precipitation variability, with some areas experiencing more intense rainfall during the monsoon season (Bangladesh Meteorological Department, 2021). Such variability exacerbates the challenge of mosquito-borne disease control.

Sea-Level Rise and Salinity: Bangladesh's low-lying coastal areas are vulnerable to sea-level rise, resulting in the intrusion of saltwater into freshwater sources. This increased salinity can create new breeding habitats for mosquitoes, as certain species can adapt to brackish water. The combination of rising sea levels and salinity intrusion presents a dual threat to coastal populations. The rate of sea-level rise in Bangladesh is approximately 3.0-4.0 mm per year, with coastal areas being the most susceptible (UNEP, 2020). As sea levels continue to rise, the potential for mosquito-borne disease transmission in coastal regions will persist.

Extreme Weather Events: Climate change has led to an increase in the frequency and intensity of extreme weather events, such as cyclones and floods, in Bangladesh. These events disrupt healthcare systems, damage infrastructure, and displace populations, making it more challenging to control and manage mosquito-borne diseases. For instance, Bangladesh has experienced an increase in the frequency and intensity of cyclones, with notable events like Cyclone Amphan causing significant damage and displacement in 2020 (Bangladesh Meteorological Department, 2021). Such disasters not only strain healthcare resources but also create conditions conducive to disease transmission.

The Impact on Public Health: The escalating mosquito-borne diseases in Bangladesh have severe implications for public health, straining the healthcare system and posing a significant burden on the population.

Disease Prevalence and Burden: Malaria, dengue fever, and chikungunya have all seen a notable increase in prevalence in recent years, leading to a higher burden on the healthcare system. This includes increased hospitalization rates and healthcare expenditures. For instance, the incidence of dengue fever in Bangladesh has risen significantly, with over 100,000 cases reported in 2019 (World Health Organization, 2020). Similarly, malaria remains endemic in some parts of Bangladesh, with an estimated 17.5 million people at risk (World Malaria Report, 2020).

Socio-Economic Impacts: The economic impact of mosquito-borne diseases is substantial, affecting households, businesses, and the national economy. Lost productivity due to illness and healthcare costs place a significant burden on families and can lead to increased poverty levels. For example, the economic cost of dengue fever alone in Bangladesh was estimated at USD 1.11 billion in 2019 (Ali et al., 2020). These costs further exacerbate the socio-economic challenges faced by the country.

Healthcare System Strain: The healthcare system in Bangladesh faces tremendous pressure during outbreaks of mosquito-borne diseases. Hospitals and clinics become overwhelmed, leading to a strain on resources and a decrease in the quality of care for patients. This places additional stress on an already resource-constrained healthcare system. For instance, dengue outbreaks in Bangladesh have led to a surge in hospital admissions, with hospitals running at or above capacity during peak periods. Such strain hampers the ability to provide adequate healthcare to affected individuals.

Adaptation and Mitigation Strategies: Addressing the escalating mosquito-borne diseases in Bangladesh requires a multifaceted approach that incorporates both adaptation and mitigation strategies.

Vector Control: Efforts to control mosquito vectors are paramount. This includes the use of insecticide-treated bed nets, indoor residual spraying, and larval source management to reduce breeding sites. These measures have been successful in reducing the incidence of malaria and can be adapted to combat other mosquito-borne diseases. Bangladesh has expanded the distribution of insecticide-treated bed nets, resulting in a decline in malaria cases (World Malaria Report, 2020). This indicates the efficacy of vector control measures.

Climate-Resilient Healthcare Systems: Building climate-resilient healthcare systems is crucial to ensure the continuity of essential services during extreme weather events and disease outbreaks. This includes strengthening healthcare infrastructure, stockpiling medical supplies, and training healthcare workers to respond effectively. The Bangladesh Ministry of Health and Family Welfare has initiated projects to improve healthcare infrastructure in flood-prone areas (Ministry of Health and Family Welfare, Bangladesh, 2021). These efforts are essential for enhancing the resilience of the healthcare system.

Public Awareness and Education: Public awareness campaigns can help educate communities on disease prevention and the importance of sanitation and hygiene. These campaigns can also inform people about the risks associated with climate change and how they can adapt to protect their health. The Bangladesh government, in partnership with international organizations, has launched educational campaigns on dengue prevention and climate change adaptation (World Health Organization, 2020). Such initiatives empower communities to take preventive measures.

Climate Change Mitigation

While adaptation measures are crucial, addressing the root causes of climate change through mitigation efforts is equally important. Reducing greenhouse gas emissions is necessary to slow down the rate of climate change and limit its adverse effects on mosquito-borne diseases in Bangladesh and worldwide. Bangladesh has made commitments to reduce its greenhouse gas emissions and has initiated various projects to promote renewable energy, energy efficiency, and afforestation (Government of Bangladesh, 2021). These efforts contribute to global mitigation goals.

International Collaboration

Addressing climate change and its impact on mosquito-borne diseases is a global challenge that requires international collaboration. Bangladesh can benefit from partnerships with other countries and international organizations to access resources, knowledge, and expertise to combat these health threats effectively. Bangladesh is a signatory to international agreements like the Paris Agreement, demonstrating its commitment to addressing climate change (UNFCCC, 2021). International cooperation is essential for tackling this transboundary issue.

Conclusion

Climate change is undeniably exacerbating mosquito-borne diseases in Bangladesh, with rising temperatures, changing precipitation patterns, sea-level rise, and extreme weather events creating favorable conditions for disease transmission. This escalation poses severe challenges to public health, the economy, and the well-being of the population. The prevalence of diseases such as dengue fever and malaria has increased significantly, with profound socio-economic impacts. The strain on the healthcare system during outbreaks further exacerbates the situation. Efforts to address this crisis must involve a combination of adaptation and mitigation strategies. These include vector control, climate-resilient healthcare systems, public awareness campaigns, climate change mitigation, and international collaboration. The involvement of government, non-governmental organizations, and the international community is essential for the effective implementation of these strategies. The case of Bangladesh serves as a stark reminder of the urgent need to address climate change at a global scale. The consequences of inaction are dire, with vulnerable populations bearing the brunt of the health-related impacts. As the world grapples with the ongoing challenges of climate change, the situation in Bangladesh underscores the necessity of immediate and sustained efforts to combat this crisis and protect human health and well-being.

Professor Dr. Ahmad Kamruzzaman Majumder, Dean, Faculty of Science, Chairman, Dept. of Environmental Science, Stamford University Bangladesh, Joint Secretary, Bangladesh Poribesh Andolon (BAPA) and Founder and Chairman, Centre for Atmospheric Pollution Studies (CAPS).