Chikungunya case cluster with nonspecific symptoms: implications for primary care in Switzerland

Summary

BACKGROUND: Early clinical presentation of chikungunya fever and other arbovirus infections is often nonspecific, potentially delaying diagnosis, particularly in settings where these diseases are less frequently considered. Competent vectors are expanding in Switzerland, increasing the risk of autochthonous arbovirus transmission.

CASE SERIES: We report seven cases in a group of travellers returning from Kenya in summer 2025. All patients presented with fever, arthralgia affecting the small joints of the hands and feet, nausea, diarrhoea, and rash. Additional symptoms included generalised lymphadenopathy and peripheral oedema. Initial diagnostic tests were inconclusive, with negative results on rapid diagnostic tests for chikungunya antibodies, dengue antibodies, and malaria antigen. The definitive diagnosis was established after 35 days following the emergence of chikungunya IgG and IgM antibodies.

DISCUSSION: The presentation resembled a nonspecific febrile illness. Repeated, appropriately timed laboratory testing was necessary to establish the diagnosis. Early diagnostic results may be misleading, particularly when testing methods are not selected appropriately for the stage of the disease. With competent mosquito vectors established in Switzerland, imported cases present a risk of local transmission. Severe infections and persistent joint pain may lead to long-term disability.

CONCLUSION: Primary care doctors should consider chikungunya fever in returning travellers and, during the mosquito-active season, in non-travellers in areas with established competent vectors. Patients may present with symptoms ranging from nonspecific febrile illness to more typical manifestations of chikungunya, including fever, arthralgia of the small joints, and rash. Appropriate test selection, timing, and repeated testing when indicated are essential for accurate diagnosis, management, and documentation of the disease.