Chikungunya is a mosquito-borne alphavirus of the Togaviridae family endemic in sub-Saharan Africa, Southeast Asia, Indonesia, the Philippines, India, and now, the Americas. The first local transmission in the Americas was reported in late 2013 on islands in the Caribbean. Many cases have since been reported in the Caribbean, especially the Dominican Republic, and throughout Central and parts of South America. The typical clinical presentation is fever and joint pain with many, but not all, patients developing a rash.

The incubation period of chikungunya is 1-14 days (usually 3-7 days). The initial symptoms consist of the abrupt onset of 3-7 days of flu-like illness with fever, chills, arthralgias, rash, myalgias, severe headache, retro-orbital pain, and photophobia. The fever is high and remitting (a fever that goes up and down without ever returning to normal). Arthralgias often precede the onset of fever in nearly three-fourths of cases. Pruritus may be noted. The rash of chikungunya may consist of widespread erythematous macules or macules and papules. The severity of disease varies across a wide spectrum. Per the CDC, approximately 3%-28% of people infected with the virus will remain asymptomatic. In a 2016 report of 110 nonpregnant adults hospitalized due to chikungunya virus infection in Guadeloupe, 42 had a severe form of disease with a syndrome consistent with severe sepsis or septic shock. Severe illness and death have also been reported in a subset of patients during other outbreaks, including on Reunion Island.

Arthralgias are typically symmetrical, involve many joints, and are migratory. They primarily affect the small joints of the hands, wrists, ankles, and feet and may last for weeks to months. Flushing of the face and trunk is seen, and then macules and papules develop on the trunk and extremities and, occasionally, the palms, soles, and face. Buccal and palatal exanthems may be present. Lymphadenopathy and sore throat may be seen in some patients. Hypocalcemia and an elevated creatine kinase level may occur in some patients. Rarely, mucosal and gastrointestinal hemorrhage may occur. Mucosal involvement is more likely in children. Neonates, elderly individuals, and those with underlying medical conditions (high blood pressure, diabetes, and heart disease) are at higher risk for severe or atypical disease.

Chikungunya is transmitted by the bite of infected mosquitoes, primarily Aedes aegypti and Aedes albopictus (which can also transmit dengue virus). Natural reservoirs include humans, primates, other mammals, and birds, but humans are the primary amplifying host (ie, humans can infect mosquitoes that bite them during the first week of illness). Person-to-person transmission of chikungunya has not been documented, although there have been reports of maternal-fetal transmission in the perinatal period in mothers with acute infection, with subsequent high levels of morbidity for the neonate. There is no evidence supporting transmission via breastfeeding. There is no specific antiviral therapy; treatment is supportive.

Travelers to endemic areas are at higher risk for contracting chikungunya. In 2014, over 1600 travel-associated cases were reported throughout the United States, resulting in 11 locally transmitted cases (all in Florida). Since then, local transmission was also identified in Texas, Puerto Rico, and the US Virgin Islands.

Vaccination (for individuals 18 years of age and older) is recommended for travelers to areas with known ongoing outbreaks. Mosquito repellents, long-sleeved shirts, long pants, etc, also help prevent bites from these aggressive, day-biting mosquitoes.