The most comprehensive mapping to date of the global risk of chikungunya suggests that India could experience 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 could be at risk of infections globally each year, with 5.1 million in India alone.
Based on existing evidence of chikungunya transmission, the analysis indicates that the virus could spread to regions not currently recording infections or considered at-risk. This could potentially increase the number of people at risk each year to 34.9 million globally, with 12.1 million in India. The study highlights that India, Brazil, and Indonesia are the top three countries most likely to experience substantial long-term impacts from chikungunya, with India and Brazil accounting for 48% of the global impact on healthcare systems and individuals.
Chronic Health Impacts and Public Health Concerns
One of the most significant findings of the study is the chronic health impacts associated with chikungunya. Existing evidence suggests that around 50% of people infected with the virus are left with long-term disability. The authors of the study emphasize that their analysis provides fresh information for public health professionals in the region, who are already working hard to contain outbreaks.
Chikungunya outbreaks have become a growing public health concern, reported in over 114 countries since its re-emergence in 2004. The virus is spread by Aedes aegypti and Aedes albopictus mosquitoes, commonly known as yellow fever and tiger mosquitoes, respectively. Infected individuals often suffer from severe joint pain and high fever, with some cases resulting in long-term joint pain and disability.
Innovative Modelling and Predictions
This study is the first of its kind to predict the burden of chikungunya using machine learning. It combines existing data on chikungunya infections with factors such as the presence of Aedes mosquitoes, suitable temperatures for virus transmission, annual precipitation, and national GDP. Previous studies have often relied on surveillance and outbreak reports, which are known to underestimate the true number of cases.
The model estimates that between 1.2-1.3% of people at risk of chikungunya could expect to be infected per year. Although this is lower than the risk of dengue, which stands at 6%, the data suggests that certain countries, such as Gabon in Africa, could experience infections in up to 11% of people at risk.
Global Implications and Future Strategies
The researchers also estimated the long-term consequences of chikungunya infection for individuals and countries worldwide. They found that India, Brazil, and Indonesia are most at risk of long-term impacts, primarily due to chronic disability rather than acute infection. Chronic illness accounted for 54% of the chikungunya burden, affecting mostly those aged between 40 and 60 years, while children under 10 and adults over 80 are most at risk of acute illness.
Hyolim Kang, who led the study, stated, “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, a co-author of the study, emphasized the importance of the modelling work being shared in real-time to help public health professionals manage current cases and prepare for the future. Meanwhile, Kaja Abbas, a senior author, noted that the model-based estimates are useful for informing outbreak response immunization strategies using the two licensed vaccines, Ixchiq® and Vimkunya®.
The researchers hope their findings can inform prevention strategies globally, such as by the WHO SAGE Working Group on Chikungunya Vaccines, to identify countries or regions at risk of long-term burden from chikungunya and to support geographical prioritization.
As the world grapples with the implications of this study, the need for effective prevention and response strategies becomes increasingly urgent. The team’s maps represent a long-term annual average and do not account for unexpected changes, such as extreme weather events and potential climate change impacts. However, the insights provided offer a crucial tool for public health officials worldwide.
