Chikungunya

Chikungunya is a mosquito-borne viral disease that causes fever and severe joint pain. It is caused by a ribonucleic acid (RNA) virus that belongs to the alphavirus genus of the family Togaviridae. The name “chikungunya” derives from a word in the Kimakonde language of southern Tanzania, meaning “to become contorted” and describes the stooped appearance of sufferers with joint pain (arthralgia).

Chikungunya virus (CHIKV) is transmitted to humans by the bites of infected female mosquitoes. Most commonly, the mosquitoes involved are Aedes aegypti and Aedes albopictus. These two species can also transmit other mosquito-borne viruses, including dengue and Zika viruses. They bite throughout daylight hours, although there may be peaks of activity in the early morning and late afternoon.

CHIKV was first identified in the United Republic of Tanzania in 1952 and subsequently in other countries in Africa and Asia. Urban outbreaks were first recorded in Asia in the 1970s, but since 2004, outbreaks of CHIKV have become more frequent and widespread. The first local, mosquito-transmitted chikungunya cases in the Americas were reported in late 2013, after which large outbreaks occurred affecting most of the countries in the region. Chikungunya has now been reported in 118 countries in Asia, Africa, Europe and the Americas. 

Symptoms of chikungunya appear between 4 and 8 days after the patient has been bitten by the infected mosquito. Chikungunya is rarely fatal. Most symptoms are generally self-limiting and last for 2–3 days. The disease is characterized by an abrupt onset of fever, which is frequently accompanied by joint pain. Other common signs and symptoms include muscle pain, headache, nausea, fatigue and rash. The joint pain is often debilitating and usually lasts for a few days to a few weeks. 

Most patients recover fully from the infection; however, occasional cases of eye, heart and neurological complications have been reported with CHIKV infections. Patients at extremes of the age spectrum are at higher risk for severe disease. Newborns infected during delivery and older people with underlying medical conditions may become severely ill and CHIKV infection can increase the risk of death. Often symptoms in infected individuals are mild and the infection may go unrecognized or be misdiagnosed in areas where dengue and other arboviruses also occur.

There is no specific antiviral drug treatment for chikungunya.

Treatment is directed primarily at relieving the symptoms, including joint pain. This is largely achieved by using anti-pyretic drugs to reduce fever, by optimizing the use of pain medication and by administering fluids. Aspirin and other non-steroidal anti-inflammatory drugs should not be administered until dengue can be ruled out to reduce the risk of bleeding. 

Prevention and control rely heavily on reducing the number of water-filled habitats that allow mosquitoes to breed. During outbreaks, insecticides may be sprayed to kill flying mosquitoes; applied to surfaces in and around water-filled habitats where the mosquitoes land; and used to treat these habitats to kill the immature larvae. There is one vaccine approved in the United States of America and in Europe for use in travelers and laboratory workers; however, the vaccine is not widely available for public health use in endemic or outbreak settings. For protection in areas of chikungunya transmission, people with risk of exposure to infected mosquitoes are advised to wear clothing which minimizes skin exposure to day-biting mosquitoes. Repellents can be applied to exposed skin or to clothing in strict accordance with product label instructions.

For those who sleep during the daytime, particularly young children or sick or older people, insecticide-treated mosquito nets afford good protection. Mosquito coils or other insecticide vaporizers may also reduce indoor biting.