The most comprehensive mapping of the global risk of chikungunya to date suggests that India could bear the greatest long-term impact from this mosquito-borne virus. Conducted by researchers from the London School of Hygiene & Tropical Medicine (LSHTM), Nagasaki University, and the International Vaccine Institute in Seoul, the study predicts that 14.4 million people globally could be at risk of infection each year, with 5.1 million of those in India.
According to the analysis, chikungunya cases could spread to regions not currently recording infections or considered at-risk, potentially increasing the global number of people at risk each year to 34.9 million, with 12.1 million in India. India, Brazil, and Indonesia are identified as the top three countries likely to experience substantial long-term impacts, with India and Brazil accounting for 48% of the global impact on healthcare systems and individuals.
Understanding the Chikungunya Threat
Chikungunya, a virus spread by Aedes aegypti and Aedes albopictus mosquitoes, causes severe joint pain and high fever in those infected. While most patients recover from the initial phase within weeks, over 50% suffer from long-term joint pain and disability, with occasional fatalities. Currently, there are no specific treatments, though two preventative vaccines have been approved in some countries.
The study’s authors emphasize the importance of their findings for public health professionals in regions like India, where efforts to contain outbreaks are ongoing. The research provides fresh insights into potential vaccine programs by mapping regions where infections could occur and identifying age groups most at risk of long-term effects.
Innovative Research and Its Implications
This study is groundbreaking in its use of machine learning to combine existing data on chikungunya infections with factors influencing infection likelihood. These factors include the presence of Aedes mosquitoes, suitable temperatures for virus transmission, annual precipitation, environmental suitability for virus spread, and national GDP levels.
Previous studies estimating the chikungunya burden often relied on surveillance and outbreak reports, which tend to underestimate actual case numbers. By predicting how many people at risk might become infected annually, the model offers a more accurate picture of the potential impact.
On average, between 1.2-1.3% of people at risk of chikungunya could expect to be infected per year, which is lower than the risk of dengue (6%). However, in countries like Gabon, infections could affect up to 11% of those at risk.
Expert Opinions and Future Strategies
Hyolim Kang, who led the study as part of her PhD at LSHTM, noted, “It’s been widely thought that mosquitoes carrying chikungunya would be confined to subtropical or tropical continents, but our analysis has found that the risk extends way beyond these regions.”
Sushant Sahastrabuddhe, Associate Director General at the International Vaccine Institute, stressed the urgency of sharing the model’s findings in real-time to aid public health professionals in managing current cases and preparing for future outbreaks.
Kaja Abbas, joint Associate Professor at LSHTM and Nagasaki University, highlighted the utility of model-based estimates in informing outbreak response immunization strategies using licensed vaccines like Ixchiq® and Vimkunya®.
Global Implications and Next Steps
The study’s findings are intended to inform global prevention strategies, such as those by the WHO SAGE Working Group on Chikungunya Vaccines, to identify at-risk regions and support geographical prioritization. The researchers caution that their maps represent a long-term annual average and do not account for unexpected changes like extreme weather events or climate change impacts.
As chikungunya outbreaks continue to pose a growing public health concern, the research underscores the need for proactive measures to mitigate the virus’s impact, particularly in regions like India, where the potential for long-term health consequences is significant.
Looking ahead, the study’s insights could prove invaluable in guiding public health policies and vaccine distribution efforts, ultimately aiming to reduce the global burden of chikungunya and protect vulnerable populations.
