The health and financial implications of the emerging threat of mosquito-borne chikungunya viral infection have most likely been significantly underestimated, with total costs probably approaching US$ 50 billion in 2011-20 alone, suggests a comprehensive data analysis, published in the open access journal BMJ Global Health.
In the short term, symptoms include fever, severe joint pain, rash and fatigue. While these often clear up, those affected can be left with long term, debilitating aftereffects, including chronic arthritic-type joint pain, fatigue, and depression, point out the researchers.
The first reported outbreak of chikungunya occurred in 1952 in Tanzania. But over the past two decades the infection has become a major public health concern, as a result of the increasing geographical spread of its vectors, Aedes aegypti and Aedes albopticus mosquitoes, explain the researchers.
"This spread, driven by factors such as globalization, urbanization, and environmental changes, significantly heightens the threat of explosive, unpredictable outbreaks in both the developed and developing world," they emphasize.
And the real prevalence of chikungunya is likely underreported due to misdiagnosis, limited diagnostic infrastructure, and issues with access to healthcare, among other things, they add.
To gauge the global health and economic impacts of the infection, with the aim of better informing preventive and infection control strategies, the researchers synthesized data from multiple sources and used advanced modelling techniques to provide a comprehensive overview of the toll taken by chikungunya between 2011 and 2020.
These sources included the Programme for Monitoring Emerging Diseases (ProMED); local ministries of health; the Pan American Health Organisation (PAHO); European Centres for Disease Control and Prevention (ECDC); the US Centers for Disease Control and Prevention (CDC); and the WHO CHOICE program.
Direct costs included those for medical care-;diagnostics, hospital stays, outpatient care, and drugs. Indirect costs referred to workplace absenteeism of patients and caregivers.
Between 2011 and 2020, 110 countries and regions reported an estimated 18.7 million chikungunya cases, once underreporting factors had been accounted for. Of these, an estimated 7.9 million (range 1.3-16.8 million), developed chronic disease.
Most of the cases were reported in Latin America and the Caribbean, where almost 15 million people were infected.
The countries with the highest number of cases were: Brazil (3.2 million); the Dominican Republic (2.7 million); and French Polynesia (1.6 million). Central and Eastern Europe, and Central Asia had the fewest cases, with 202 spread over six countries and mainly attributable to travelers returning from endemic areas.
Globally, an estimated 13,000 people died of their infection in its acute phase (range 2,242 to 336,286).
Cases reached a peak of 8.7 million in 2014 when outbreaks were reported in the Dominican Republic, Guadeloupe, French Polynesia, French Guiana, and several Caribbean islands.
Estimates of the total number of DALYS (disability adjusted life years)-;years of life lost because of a disability/illness/death-;totaled 1.95 million, equivalent to an average yearly loss of 195,000.
Chronic disease made up most of this total:1.5 million (76%) DALYs; acute illness accounted for the rest: 476,000 (24%).
The highest number of DALYs was in 2014-16, with 913,000, 432,000, and 262,000, respectively, in each of those years, reflecting major chikungunya outbreaks. DALYs also peaked in 2019, reaching 131,000.
Latin America and the Caribbean accounted for 80% of the total DALYs (1.6 million), followed by Southeast Asia, East Asia, and Oceania, which accounted for 12% of the total (237,000).
Brazil topped the league table of DALYs, racking up 329,000, and contributing 17% of the global total between 2011 and 2020.
The researchers estimated that the financial toll of chikungunya between this period was US$ 49.9 billion, comprising US$ 25.1 billion for chronic disease and US$ 24.8 billion for acute illness.
Total direct costs came to US$ 2.8 billion (6% of the total), and total indirect costs came to US$ 47.1 billion (94%). Absenteeism was the main driver of both types of cost. The global average cost of each case was US$ 2700.
Once again, Latin America and the Caribbean bore the brunt of these costs.
The researchers acknowledge that the quality and availability of data varied across countries, and the modelling relied on certain assumptions and simplifications due to data constraints, all of which may have influenced the precision of the estimates.
And the estimates represent only a snapshot of the health and economic toll taken by chikungunya during a specific time period and so may not have accurately captured changes over time, they add.
But they nevertheless state: "Our study reveals a substantial economic and health burden of chikungunya worldwide, especially in Latin America and the Caribbean.
"[These] regions had the highest DALY and cost burden, mainly due to the high case numbers in Brazil, the Dominican Republic, and Colombia, reflecting the rapid expansion in a naïve population since [the] introduction [of the chikungunya virus] in 2013."
And they conclude: "The health and economic burden of chikungunya is substantial, and might be underestimated up until now. Especially considering its potential to cause explosive outbreaks and considerable long-term health consequences, it is crucial to have a thorough understanding of this disease."
Research suggests no need for yellow fever vaccine booster after initial dose