Chikungunya virus (CHIKV) is a mosquito-borne alphavirus transmitted by Aedes aegypti and Aedes albopictus. Despite favorable ecological conditions in southern Iran, data on CHIKV exposure in Bushehr Province are lacking. This study aimed to determine the seroprevalence of CHIKV-specific IgG antibodies and assess potential viral circulation. A cross-sectional seroepidemiological survey was conducted from July to September 2023 in ten cities across Bushehr Province. Serum samples (n = 180) collected from volunteers at hospitals and blood donation centers were tested for CHIKV-specific IgG antibodies using a commercial ELISA kit. Of the 180 serum samples analyzed, five tested positive for CHIKV IgG antibodies, yielding an overall seroprevalence rate of 2.78%. Seropositive individuals were identified in Bushehr, Dashtestan, and Dashti cities, indicating localized and possibly silent transmission. This study provides the first serological evidence of CHIKV exposure in Bushehr Province. The findings underscore the potential for local transmission in areas where competent Aedes vectors are present and highlight the urgent need for sustained vector surveillance, early warning systems, and public health preparedness in southern Iran.

Chikungunya virus (CHIKV) is an arthropod-borne alphavirus that causes an abrupt febrile illness typically marked by intense arthralgia, rash, and profound fatigue. Following transmission predominantly through Aedes mosquitoes, the virus is able to infect a broad range of host cell types, such as fibroblasts and macrophages, resulting in acute viremia with high viral titers and, in a subset of patients, prolonged arthritis-like manifestations. CHIKV carries a positive-sense, single-stranded RNA genome that encodes nonstructural proteins essential for viral replication as well as structural components required for virion assembly and host-cell entry. The MXRA8 receptor has recently been identified as a central determinant of viral entry and cellular tropism. Genomic analyses place CHIKV into three major lineages, and certain amino-acid substitutions, most notably the E1-A226V change, have been linked to improved adaptation to Aedes vectors and more efficient transmission. The host immune reaction is multifaceted, involving type I interferons, neutralizing antibodies, and virus-specific T-cell activity. Even so, the virus is able to bypass several of these defenses through established evasion mechanisms, which may contribute to prolonged infection in some cases. Given the continued expansion of Aedes mosquito populations driven by climate change, integrated vector-management strategies remain essential. These include chemical, biological, and genetic approaches aimed at curbing mosquito densities and reducing the impact of insecticide resistance. Sustained global surveillance and coordinated public-health interventions are critical to mitigating the growing burden of CHIKV and addressing the recent surge in large-scale outbreaks.