Chikungunya in Seychelles

Acknowledgement
This report is published on behalf of the GeoSentinel Office of the Principal Investigator. GeoSentinel is a cooperative agreement U01CK000632-01-00 between the US Centers for Disease Control and Prevention (US CDC) and the International Society of Travel Medicine (ISTM).

Author
David Hamer, MD. GeoSentinel Surveillance Lead; Professor of Global Health and Medicine, Boston University School of Public Health and School of Medicine, Boston, MA, USA.

Key findings

• From 2005 to 2025, the GeoSentinel surveillance network has detected only two PCR (polymerase chain reaction)-confirmed cases of chikungunya virus disease among European travelers returning from the Seychelles, both acquired in 2007.
• A PCR-confirmed case emerged in June 2025 among a traveler returning from the Seychelles. Single probable cases (serologically confirmed) followed in August and October 2025.
• Following a brief interval, an abrupt surge occurred from early December 2025 through 30 Jan 2026, with nine confirmed and four probable cases (13 total) reported among ill travelers returning from the Seychelles.
• Across all 16 cases, 13 involved tourists, while the purpose of travel was undetermined for the remaining 3. All patients presented at GeoSentinel sites in Europe upon their return and were European residents.

Epidemiological analysis and public health impact

• The clustering of cases among returning travelers strongly suggests an acute increase in chikungunya transmission in the Seychelles in recent weeks, making this a location where preventive measures for travelers are advisable. A nationwide rise in chikungunya cases since mid-December 2025 has also been recognized by the Seychelles Ministry of Health.
• Travelers to the Seychelles should receive enhanced counseling before departure, including vaccination where available and strict adherence to mosquito-bite prevention measures. Two licensed chikungunya vaccines are available for traveler protection, though availability varies by country: IXCHIQ (live-attenuated vaccine, Valneva) and VIMKUNYA (virus-like particle vaccine, Bavarian Nordic).
• These cases among returning European travelers underscore the value of robust travel medicine networks like GeoSentinel in detecting transmission dynamics and trends in destination countries.

Comparative analysis and future outlook

• The current situation is a concerning parallel to the 2005–2007 epidemic, when Seychelles experienced its first major chikungunya outbreak. Following nearly 20 years without significant activity, the current rise in cases suggests the virus has been reintroduced to the islands, possibly as part of the broader regional outbreak affecting the Indian Ocean region.
• The presence of Aedes mosquitoes throughout the islands provides the vector infrastructure for sustained transmission, while the tropical climate supports year-round mosquito breeding. Seychelles’ tourism-dependent economy continuously introduces susceptible visitors who can acquire chikungunya and may export the virus internationally.