Chikungunya in Spain

Acknowledgement
BEACON thanks Drs. Francesca Norman and Jose A. Perez-Molina at the GeoSentinel Madrid site, Hospital Ramón y Cajal, Madrid, Spain, and Dr. Davidson Hamer, Surveillance Lead for the GeoSentinel Surveillance Network, Boston University School of Public Health, for this submission.

Key findings

Chikungunya was diagnosed in two recent travelers returning to Madrid, Spain, after visiting Santa Cruz Department in Bolivia.

Case 1

• The first patient, a 22-year-old woman, was in Santa Cruz from 11 to 20 Jun 2025. She developed a fever, headache, arthralgias, generalized edema or swelling, and a rash on 19 Jun 2025.
• The self-reported rash lasted for seven days, and she continued to experience persistent arthralgias until July 2025.
• Based on positive serological tests for anti-chikungunya virus IgM and IgG (polymerase chain reaction (PCR) was negative), she was diagnosed with probable chikungunya when evaluated in Madrid on 16 Jul 2025.
• Her grandmother was diagnosed with chikungunya in Bolivia at the same time.

Case 2

• The second patient was a 57-year-old woman who traveled to Santa Cruz from 22 Apr to 21 May 2025.
• She developed fever, arthralgia, myalgia, headache, pruritus, and generalized edema/swelling without a definite rash. She continued to have persistent arthralgias and was seen in the tropical medicine center in Madrid on 06 Jun 2025 with persistent arthralgias, mainly in her ankles.
• Her initial PCR test was negative for chikungunya virus, but both anti-chikungunya virus IgM and IgG were positive.
• Follow-up testing three weeks later showed a twofold increase in her IgG titer and a decrease in IgM, thus serologically confirming the diagnosis.

Epidemiological analysis and public health impact

• By Week 33 of 2025 (mid-August), the Pan American Health Organization (PAHO) reported 5162 total chikungunya cases in Bolivia. This marks a significant increase from the 505 cases in 2024. However, case numbers seem to be decreasing in recent weeks through August and September.
• Laboratory-supported diagnoses in returning travelers described in this report have compatible symptoms and timing, providing strong evidence of ongoing local chikungunya transmission in Santa Cruz during mid-2025.
• Both cases demonstrate typical clinical features (fever, arthralgia, rash, and edema), and notably, persistent arthralgias lasting weeks to months—a recognized sequela of chikungunya virus infection—were documented.
• Chikungunya virus (CHIKV) is transmitted by Aedes mosquitoes, favoring tropical and urban environments common in Santa Cruz, which has previously reported cyclical arboviral outbreaks.
• Persistent symptoms in these imported cases suggest a potentially high rate of long-term health issues among affected individuals, with significant public health consequences for both the countries affected and those welcoming returning travelers.

Comparative and future outlook

• The primary concentration of cases in Santa Cruz aligns with earlier regional patterns, where factors such as climate, urban density, and vector presence influence arboviral transmission cycles.
• The exportation of cases to Spain indicates ongoing risks to travelers and the potential for continued international spread, particularly affecting individuals who are more likely to stay in residential areas.
• In 2024, Spain reported eight cases in the province of Tarragona. Recently, other EU countries such as France and Italy have reported increasing numbers of autochthonous chikungunya cases, often as local clusters around returning travelers.
• The mosquito vector, Aedes albopictus, has established itself in Spain, especially in Valencia, since 2013. This makes local transmission possible, even if it hasn’t been confirmed as widespread.