Is Climate Change Causing a Rise in Dengue?

Introduction

Amidst Malaysia's lush green landscapes and tropical warmth, the fight against dengue fever has proven to be a persistent challenge.

Despite Malaysia's unwavering efforts to control the spread of this disease, tackling the pesky mosquitoes that transmit dengue through their bites has proven to be an uphill task.^[1]

Public health expert Dr. Rohaida Ismail suggests a connection between the Earth's rising temperatures and the increased threat of vector-borne diseases.^[2]

In this article, we aim to examine the impact of climate change on the surge of dengue in Malaysia, recognizing the complexities and uncertainties surrounding this relationship.

Understanding Dengue Fever

As stated by the World Health Organization (WHO), dengue, also commonly known as breakbone fever, is a prevalent viral infection that is transmitted to humans by the infected Aedes mosquito.^[3]

Its prevalence has significantly risen in recent decades in tropical countries. While most individuals experience no symptoms and recover quickly, some can develop a severe form (dengue haemorrhagic fever or dengue shock syndrome) that require hospitalisation.^[3],[4] 

Dr. Velayudhan, at a United Nations briefing in Geneva, highlighted that severe dengue can turn fatal, particularly when individuals are infected a second time.^[5]

Climate Change and Dengue: Knowing the Impact

Malaysia is experiencing extreme weather events attributed to climate change, including floods and shifts in monsoons. Driven by rising temperatures, the Aedes mosquitoes, responsible for dengue transmission, mature more quickly, and their breeding grounds multiply due to prolonged weather patterns.^[2]

Climate change hazards that are said to affect the dengue virus also include:^[6]

1. Warmer Weather: Higher temperatures lead to an increase of reproduction and growth of mosquitoes, as well as the frequency of mosquito bites.
2. Humidity: High humidity helps Aedes mosquitoes live longer and lay more eggs.
3. Rain and Flooding: Excessive rain and flooding create more breeding spots for Aedes mosquitoes.
4. Drought: Even during dry spells, water stored in containers can become breeding sites.

However, it's crucial to note that the link between climate change and the rise of dengue is not entirely straightforward.

The Rise of Dengue in Malaysia

Dengue can be more common during the June to September monsoon season as mosquitoes thrive in stagnant water.[7] With Malaysia already witnessing dengue outbreaks, the worsening climate may make matters more dire.^[1]

According to a statement from The Star dated Thursday, 08 Feb 2024, Datuk Dr. Muhammad Radzi Abu Hassan, the Director-General of Health, reported a significant increase in suspected dengue cases. He mentioned that during the initial five weeks of 2024, there were 18,247 cases recorded, marking a 65.6% surge compared to the 11,127 cases reported during the same period last year.^[8]

To date, the fatalities due to this severe disease have increased to 67 compared to 28 reported in the corresponding period in 2022.^[8]

A study by the Infectious Disease Modelling Journal discovered that the number of dengue infections in Selangor, is expected to climb in the future.^[9]

Based on a disease transmission model, the study projected the dengue fever epidemic until the 2090s, indicating that the daily dengue incidence in Selangor will grow from 487 cases per day in the 2030s to 668 cases per day in 2090.^[9]

More Than Just Dengue

The impact of climate change on disease vectors extends beyond mosquitoes to include ticks, which can transmit various pathogens, posing additional public health risks. The COVID-19 pandemic has further highlighted the interconnectedness of climate, disease, and public health.

Protecting You and Your Loved Ones

In the past, Aedes mosquitoes primarily targeted children as their victims. However, as time has passed, the age range of infections in Southeast Asia has shifted, affecting individuals between 15 and 45 years old, many of whom are in their childbearing years.^[1]

Adaptation strategies tailored to the changing of all vector carrying disease dynamics are crucial. There are additional actions we must implement to adapt to these growing risks:^[10]

• Ensure Universal Access to Care and Disease Management: Making healthcare and disease management accessible to all is vital.
• Reduce Vector Exposure: Measures like using window and door screens, wearing protective clothing, deploying insecticides, and avoiding habitats where disease vectors breed can minimise exposure.
• Accelerate Vaccine Development: Leverage new technologies to expedite the development of vaccines against these viral diseases.
• Prioritise Wetland Management: Focus on managing wetlands and eliminating breeding sites for disease-carrying vectors near populated areas.

Conclusion

Climate change affects the entire world and Malaysia is no exception. In recent years, dengue fever, a virus transmitted through mosquitoes, has re-emerged considerably, affecting a significant number of people each year. While climate factors, such as temperatures, rainfall, and humidity, have been linked to dengue viruses, such connections are inconsistent.

While dengue prevention is important, tackling the effects of climate change also depends on each and every one of us. By minimising our carbon imprint, progressively phasing out petroleum, and selecting natural energy sources, we can participate actively in tackling this worldwide issue towards a healthier and more prosperous future for generations to come.

References

1. Yeong, A. (2022). Climate change creates the perfect conditions for dengue to spread: Is fogging enough to beat that? Retrieved on 25 October 2023, from Malay Mail: https://www.malaymail.com/news/malaysia/2022/12/27/climate-change-creates-the-perfect-conditions-for-dengue-to-spread-is-fogging-enough-to-beat-that/46953
2. Unair News. (2022) Malaysian Ministry of Health reveals climate change increases the risk of vector-borne disease. Retrieved on 25 October 2023, from Unair News: https://news.unair.ac.id/2022/02/04/malaysian-ministry-of-health-reveals-climate-change-increases-the-risk-of-vector-borne-disease/?lang=en
3. World Health Organization. (2023). Dengue and severe dengue. Retrieved on 25 October 2023, from WHO: https://www.who.int/news-room/questions-and-answers/item/dengue-and-severe-dengue
4. Mayo Clinic. (2022) Dengue fever - Symptoms and causes. Retrieved on 25 October 2023, from Mayo Clinic: https://www.mayoclinic.org/diseases-conditions/dengue-fever/symptoms-causes/syc-20353078
5. UN News. (2023). Spike in dengue cases due to global warming, warns WHO. Retrieved on 25 October 2023, from UN News: https://news.un.org/en/story/2023/07/1138962
6. Marano, M. (2023, October 19). The Increasing Burden of Dengue Fever in a Changing Climate. Retrieved on 25 October 2023, from The Rockefeller Foundation: https://www.rockefellerfoundation.org/blog/the-increasing-burden-of-dengue-fever-in-a-changing-climate/
7. Thomson Reuters Foundation (2023). Global warming, longer monsoon rains making dengue deadlier in South Asia. Retrieved on 25 October 2023, from Al Jazeera: https://www.aljazeera.com/news/2023/9/8/global-warming-longer-monsoon-rains-making-dengue-deadlier-in-south-asia
8. YUNUS, ARFA. “Dengue cases up by 65%.” The Star, 8 February 2024,Retrieved on 23 February, from Star: 2024.https://www.thestar.com.my/news/nation/2024/02/08/dengue-cases-up-by-65. 
9. Wang, Y., Zhao, S., Wei, Y., Li, K., Jiang, X., Li, C., Ren, C., Yin, S., Ho, J., Ran, J., Han, L., Zee, B. C. Y., & Chong, K. C. (2023, September). Impact of climate change on dengue fever epidemics in South and Southeast Asian settings: A modelling study. Infectious Disease Modelling, 8(3), 645–655. https://doi.org/10.1016/j.idm.2023.05.008
10. Wellcome. (2022). How climate change affects vector-borne diseases. Retrieved on 25 October 2023, from Wellcome: https://wellcome.org/news/how-climate-change-affects-vector-borne-diseases

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Disclaimer: These images depict hypothetical patients and/or healthcare professionals. This information is available to the public for information purposes only; it should not be used for diagnosing or treating a health problem or disease. It is not intended to substitute consultation with a healthcare provider. Please consult your healthcare provider for advice.

C-ANPROM/MY/DENV/0279 March 2024