The geographic confines of the Chikungunya (CHIK) virus, which has been considered a tropical virus, now stand broken, with increasing world travel and global warming. Recently, an outbreak of cases in Italy was reported. The CHIK virus is predominantly a resident of Africa and Asia, and the last major outbreak of CHIK virus infection originated in Reunion Island (near east Africa). On January 3, 2007, the number of cases of CHIK virus infection in India was 1,391,165 (1). The epidemic had returned after 32 years (2, 3). Tragically, the timing coincided with an outbreak of dengue fever. Both CHIK infection and dengue fever are self-limited, febrile, mosquito (Aedes species)–borne arboviral illnesses, characterized by arthralgias and frequently arthritis. Although severe backache (bone-breaking fever) characterizes dengue fever, severe arthralgias are the rule in CHIK infection. However, unlike dengue fever, CHIK (alphavirus genera) infection has not conclusively been proven to be fatal. The duration of the acute illness (4) rarely exceeds 10 days, and other features include inflammatory arthritis, debilitating fatigue, and sometimes a transient skin rash (vasculitis). Uncommonly, chronic arthralgias and arthritis may continue (5), but very few followup data have been published. Here, we report our experience with CHIK virus infection and its lingering rheumatic musculoskeletal sequelae, from a rheumatology referral center in the western Indian state of Maharashtara.

During the period from July 2006 to December 2006, 156 patients (105 of whom were women and 3 of whom were children) continued to have chronic musculoskeletal illness following CHIK virus infection. Ninety-five patients (59 of whom were women) who were naive for musculoskeletal disorders were labeled as having post-CHIK musculoskeletal relapse. The remaining 61 patients (45 with rheumatoid arthritis [RA], 8 with undifferentiated inflammatory arthritis, and 8 with seronegative spondylarthritis [SpA]) were considered to have a relapse of their earlier illness and were labeled as having pre-CHIK musculoskeletal relapse. The diagnosis of CHIK infection was essentially clinical, supported by a similar occurrence in several family members during the epidemic period. We excluded several tropical infections (dengue fever and malaria in particular). Anti-CHIK IgM antibodies were detected using a single-serum monoclonal antibody-capture