Climate-Driven Barriers to Polio Eradication: A Case Study in Pakistan

BY LANXI LIN

As the world edges closer to eradicating infectious diseases, the Middle East remains a battleground, where rising temperatures and extreme weather events fueled by climate change are threatening to undo decades of progress in public health vaccine efforts. Pakistan, a Middle Eastern country nestled between India and Afghanistan, is one of the few countries with ongoing endemic poliomyelitis (polio), a highly contagious viral disease primarily targeting the nervous system caused by the poliovirus with mild flu-like symptoms to severe paralysis. Polio is an enteric disease, meaning it is predominantly transmitted through the fecal-oral route (ingesting contaminated food or water), with children under the age of five being the most susceptible. While a very deadly and contagious disease, polio vaccines have long been in circulation. After Jonas Salk developed the first polio vaccine in the 1950s, polio cases have declined dramatically from 350,000 cases in 125 countries to only seven reported cases in 2023¹. Yet, six out of those seven reported cases were solely from Pakistan. From these data, it might be logical to conclude that there is not enough global investment in eradicating polio in this region, but this is far from the truth. Over $160 million has been invested by the Islamic Development Bank for the polio vaccination of 43 million children in Pakistan¹. Furthermore, the World Health Organization (WHO) and United Nations Children’s Fund (UNICEF) have invested $20 billion since the 1988 launch of the Global Polio Eradication Initiative⁷. However, all the efforts towards eradication have been severely hampered by the rising temperatures of global warming and the increasing frequency and severity of weather conditions such as monsoons and droughts. Climate change in Pakistan has caused increased demand for polio vaccines due to rising temperatures, which has increased the severity of natural disasters.

A foremost aspect of climate change is the consequence of global warming caused by high levels of greenhouse gases. Pakistan is one of the most vulnerable regions to temperature swings, with temperatures rising to 122 degrees Fahrenheit in 2022 when the average summer temperature is only 100 degrees Fahrenheit⁶. While these warmer temperatures might have apparent effects on population health, climate models have estimated an increase in polio outbreaks with the rising temperatures. “In the worst-case scenario, we find that epidemic peak size could increase by up to 40% due to climate change, depending on location and climate model.”⁹ Warmer temperatures support the survival and transmission of fecal-oral route diseases; therefore, warmer winters could lead to abnormal seasonal spikes in transmission and the year-round spread of the virus. Greater seasonal temperature fluctuations could result in larger summer outbreaks and longer recovery times for susceptible populations, leading to more frequent outbreaks. Despite Pakistan’s negligible carbon emissions compared to other countries, the country has suffered the most from the impacts of global warming due to a deadly disease.

One of the reasons we see this increase in transmission can be narrowed down to more monsoons, which lead to greater water contamination and higher mosquito transmission. Climate change poses a serious threat as the recent monsoons have been worse than ever, increasing the risk of waterborne diseases and making it impossible to control polio transmission. Climate change alters precipitation patterns, leading to flooding, droughts, and tropical storms that can compromise water quality and increase the spread of infectious diseases such as polio². Specifically, in 2022, Pakistan experienced unmatched monsoon flooding that left millions without medical care and destroyed approximately 888 health facilities¹. While these floods destroy homes and displace populations, the most concerning aspect is that increased flooding can jeopardize the water quality and sanitation system, causing the underwater sources to become a likely origin of contamination for new polio outbreaks. In 2022’s severe monsoon, the number of reported cases in Pakistan shot up to 15 from only one case in 2021¹. This uprise in cases is likely correlated to “5.4 million people rely solely on contaminated water”¹⁰. UNICEF believes that if the weather conditions keep worsening, polio will never be truly eradicated¹⁰. Weakened sanitation systems, in tandem with increased monsoons, are disastrous for polio control efforts.

The increase in severe weather conditions, such as monsoons, not only enhances transmission but, most importantly, hinders vaccination coverage, causing distrust in polio workers. Vaccination campaigns had to halt due to the floods of the 2022 monsoon in Pakistan, as a third of the country was submerged and millions were displaced¹⁰. Immunization campaigns were disrupted as workers could only administer vaccines by trudging through the deep waters. Pakistan leads with one of the highest child mortality rates, likely due to its low national vaccination average of 60.6%, even though “vaccine-preventable deaths constitute nearly half of all deaths in Pakistan.”¹⁵ This issue of climate change breaks down the core efforts to prevent further polio cases. The food insecurity, economic hardship, and displacement of families due to natural disasters increase the people’s frustration with government response and consequently increase skepticism in public health initiatives such as vaccination programs.

Polio eradication is very straightforward in principle, but climate change is making it much more complicated. Without addressing the broader effects of climate change on public health through climate-resilient vaccination programs and disaster response strategies, Pakistan will struggle to eliminate polio permanently.

These issues associated with climate change haunt the goal of ending the polio virus in Pakistan and similar struggling nations because the world appears to be working against eradication by letting climate change persist and worsen. The sad truth of the impact of climate change, increasing polio cases, and thwarting interventions is that it is the same group of underrepresented individuals suffering the greatest from the effects of climate change and the never-ending, looming presence of a deadly disease. Children from low-income countries are caught in the vicious cycle of malnutrition and illness due to food insecurity and underpreparedness for the effects of climate change. If we allow climate change to accelerate unchecked, it will continue to hit the most vulnerable children in low-income countries first and hardest, but ultimately, no one will be spared. Climate change is another brewing disease that will continue to progress to a point where it will affect us all, no matter the country, race, or status. Copious amounts of time, resources, and money have been put into polio eradication that cannot go to waste. We cannot give up now.

Lanxi Lin is a sophomore in Morse College.

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References

1. Lives and Livelihoods Fund. Climate Change – A potent threat to polio eradication. https://www.livelivelihoods.org/news/climate-change-a-potent-threat-to-polio-eradication (2023).
2. Hong, C.-C. et al. Causes of 2022 Pakistan flooding and its linkage with China and Europe heatwaves. npj Clim. Atmos. Sci. 6, 163 (2023).
3. Bhutta, Z.A. Conflict and Polio: Winning the Polio Wars. JAMA 310, 905–906 (2013).
4. Nagata, J.M., Epstein, A., Ganson, K.T., Benmarhnia, T. & Weiser, S.D. Drought and child vaccination coverage in 22 countries in sub-Saharan Africa: A retrospective analysis of national survey data from 2011 to 2019. PLoS Med. 18, e1003678 (2021).
5. Deshpande, J.M., Shetty, S.J. & Siddiqui, Z.A. Environmental surveillance system to track wild poliovirus transmission. Appl. Environ. Microbiol. 69, 2919–2927 (2003).
6. Somani, R. Global warming in Pakistan and its impact on public health as viewed through a health equity lens. Int. J. Soc. Determinants Health Health Serv. 53, 154–157 (2023).
7. Global Polio Eradication Initiative. Historical Contributions. https://polioeradication.org/donors-financing/historical-contributions/.
8. Global Polio Eradication Initiative. Pakistan’s fight to end polio amid the climate crisis. https://polioeradication.org/news/pakistans-fight-to-end-polio-amid-the-climate-crisis/.
9. Baker, R.E., Yang, W., Vecchi, G.A. & Takahashi, S. Increasing intensity of enterovirus outbreaks projected with climate change. Nat. Commun. 15, 6466 (2024).
10. UNICEF. Polio | UNICEF Pakistan. https://www.unicef.org/pakistan/polio.
11. Polio Vaccination: Past, present and future. Future Microbiol. 10, 563–566 (2015). https://www.tandfonline.com/doi/metrics/10.2217/fmb.15.19
12. Rodriguez, D.C. et al. The effects of polio eradication efforts on health systems: A cross-country analysis using the Develop–Distort Dilemma. Health Policy Plan. 36, 707–719 (2021).
13. Chitre, S.D. et al. The impact of anthropogenic climate change on pediatric viral diseases. Pediatr. Res. 95, 496–507 (2024).
14. The Impact of Climate Change on Vaccine-Preventable Diseases: Insights From Current Research and New Directions. (Missing publication details—please provide to format properly).
15. Zarzeczny, A. & Kahar, P. Vaccine trends in Pakistan: A review of immunization challenges and setbacks prompted by inadequate disaster management. Cureus 16, e55357 (2024).