Rapid #risk #assessment: #Chikungunya virus disease, #Global (WHO, 24 April 2026, v2, summary)

{Summary)

Overall Risk statement

-- This rapid risk assessment aims to assess the overall public health risk posed by chikungunya virus (CHIKV) transmission in 2026 at the global level. 

-- It considers the potential risk to human health, the likelihood of geographical spread, limitations in prevention and control capacities, and the influence of regional seasonal patterns that favour Aedes mosquito activity, which could drive outbreaks during the 2026 transmission season. 

-- Chikungunya virus poses a significant and growing global health risk due to large and widespread regional outbreaks in recent years, lack of specific treatment, limited use of vaccine, and climate- and conveyance-driven mosquito range expansion, with increasing international travel. 

-- While mortality remains relatively low, the CHIKV infection can cause prolonged arthritis with disability as well as severe illness in some patients.

-- In 2025, an overall of 502 264 CHIKV disease cases including 208 335 confirmed cases, and 186 deaths were reported globally from 41 countries and territories, including autochthonous and imported cases in travellers. 

-- From 1 January to 31 March 2026, Chikungunya transmission was reported by 18 countries, with the vast majority of cases occurring in the Region of the Americas. 

-- Brazil and Bolivia account for 87% of cases in the Region; together with Argentina, Suriname, and Cuba, these five countries represent approximately 99% of reported cases. 

-- The European Region reported the second-highest number of cases, predominantly reported from French overseas departments, particularly Mayotte and La Réunion. 

-- Global aggregation is limited due to incomplete reporting.

-- With the rainy season about to begin in many regions in the coming months, cases of CHIKV are expected to rise, as rainfall events create favourable conditions for Aedes mosquito breeding and increase the risk of CHIKV transmission, including in previously unaffected areas. 

-- Transmission dynamics will also be impacted by the population immunity acquired from outbreaks in recent years. 

-- Peak CHIKV transmission months in the respective WHO regions include:

• Southeast Asia & Western Pacific: May–October

• Americas: May–November (Northern hemisphere)/November–March (Southern hemisphere)

• Continental Europe: June–September (main season) (transmission in overseas departments aligns with climatic conditions within their geographic location/proximity)

• Africa & Eastern Mediterranean: During/after local rainy seasons (varies by country)

-- The global public health risk posed by CHIKV transmission is assessed as moderate. 

-- This takes into account the widespread transmission and outbreaks across multiple WHO regions in 2025, which continued into early 2026, including in areas with previously low or no transmission. 

-- Ongoing transmission in parts of the Indian Ocean region, such as Seychelles, Mauritius and Mayotte demonstrates continued regional activity. 

-- The resurgence and emergence of cases in new geographic areas are facilitated by the presence of competent Aedes mosquito vectors, limited population immunity, favorable environmental conditions, and increased human mobility coupled with under-performing/disrupted health systems, particularly in fragile, conflict-affected and vulnerable countries- leading to poor control measures.

-- The uneven distribution of cases across regions complicates the interpretation of a global trend but highlights significant localized transmission. 

-- Prevention and control capacities remain challenged by gaps in surveillance, equitable access to quality-assured diagnostics and laboratory confirmation, healthcare infrastructure, and sustained vector surveillance and control management.

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Source: 

Link: https://www.who.int/publications/m/item/who-rapid-risk-assessment---chikungunya-virus-disease--global-v.2

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