Fever and Prominent Arthralgia in a Traveler who Returned from Amazonia: Differentiating between Dengue Fever and Chikungunya Fever

which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Correspondence Dear Editor, We read the case of Chikungunya fever (CF) reported by doctors Hwang and Lee with interest [1]. We report a similar case, but from western South America. CF cases have been reported in western Europe, South America, Africa, and most recently in the Caribbean. Clinically, CF is characterized by persistent severe arthralgia [2]. In South America, CF, Mayaro fever (MF), and dengue fever (DF) share a similar geographic distribution and may resemble each other. CF, MF, and DF present with fever, chills, headache , myalgias/arthralgias, and rash. Arthralgias in CF typically persist for months, while those in MF and DF are usually transient and self-limited [3]. Serum transaminase and eryth-rocyte sedimentation rate (ESR) elevations are common in CF, MF, and DF [2, 4-6]. A 37-year-old man travelled to western South America, including Ecuador, Colombia, Peru, Bolivia, and the Peruvian Amazon for 8 months (fall 2012 to spring 2013). He suffered many mosquito bites during his travels. Subsequently, he developed a fever of 39.5℃, chills, headache, myalgias, and severe arthralgias in June 2013. His fever abated within 6 days, but severe joint pains, involving the hands and wrists, persisted. Laboratory tests included a normal white blood cell count, platelet count, and ESR. Serum transaminases were unelevat-ed. Leptospira spp., Rickettsia spp., and Brucella spp. titers were negative. Dengue immunoglobulin (Ig) G and IgM titers were negative. The mayaro virus (MV) IgM titer was negative and the MV IgG titer was positive (untitered enzyme-linked immunosorbent assay by US CDC). The chikungunya virus (CV) IgM titer was negative and the CV IgG titer was elevated to 1:320. Severe small joint arthralgias persisted for months. MF is endemic in South American countries (e.g., Peru and Brazil). Clinically, MF presents as a dengue-like illness with fever, myalgias, arthralgias, and rash, or may resemble CF. Ar-thralgias in MF are usually of short duration, i.e., 3-5 days, but may last weeks. Although our patient had elevated MV IgG and CV IgG titers, which are typically found in CF, severe ar-thralgias persisted for months [7-10]. Although MV IgG titers were positive, we believed that the patient's clinical course was characteristic of CF. CF had not been reported previously