Chikungunya is a viral disease transmitted to humans through the bites of mosquitoes infected with the chikungunya virus. It was first described during an outbreak in southern Tanzania in 1952 and has now been identified in nearly 40 countries in Asia, Africa, Europe and, most recently, the Americas. Symptoms usually begin 4 to 8 days after a mosquito bite but can appear anywhere from 2 to 12 days. The most common symptom is an abrupt onset of fever, often accompanied by joint pain. Other symptoms include muscle pain, headache, nausea, fatigue, and rash. Severe joint pain usually lasts a few days but can persist for months or even years. Serious complications are uncommon, but in older people, the disease can contribute to the cause of death. There is no vaccine or antiviral drug treatment for chikungunya. Treatment is focused on relieving the symptoms.