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CHIKUNGUNYA

What is Chikungunya?
How do humans become infected with chikungunya virus?
What are the symptoms?
How is it diagnosed?
How is it treated?
How to prevent Chikungunya?
 
Wednesday, 03 June 2009
Written by : DoctorNDTV Team
 
What is Chikungunya?
What is Chikungunya?Chikungunya is a relatively rare form of viral fever caused by an alphavirus that is spread by mosquito bites from the Aedes aegypti mosquito. The name is derived from the African word meaning ‘that which bends up’ in reference to the stooped posture developed as a result of the arthritic symptoms of the disease. The disease was first described by Marion Robinson and W.H.R. Lumsden in 1955, following an outbreak on the Makonde Plateau, along the border between Tanganyika and Mozambique, in 1952. Chikungunya is not considered to be fatal. Chikungunya virus is highly infective and disabling but is not transmissible between people.

Epidemiology

Chikungunya was first described in Tanganyika, Africa in 1955. An outbreak of chikungunya was discovered in Port Klang in Malaysia in 1999 affecting 27 people. In February 2005, an outbreak was recorded on the French island of Réunion in the Indian Ocean. As of 18 May 2006, 258,000 residents have been hit by the virus in the past year (out of a population of about 777,000). 219 official deaths have been associated with chikungunya). In Mauritius, 3,500 islanders have been hit in 2005.

There have also been cases in Madagascar, Mayotte and the Seychelles. In 2006, there was a big outbreak in the Andhra Pradesh state in India. Nearly 200,000 people were affected by this disease in the districts of Praksham and Nellore in this state. Some deaths have been reported but it was thought to be due mainly to the inappropriate use of antibiotics and anti inflammatory tablets. As this virus can cause thrombocytopenia, injudicious use of these drugs can cause erosions in the gastric epithelium leading to exsangunating upper GI bleed (due to thrombocytopenia).

A separate outbreak of chikungunya fever was reported from Malegaon town in Nasik district, Maharashtra state, in the first two weeks of March 2006, resulting in over 2000 cases. In Orissa state, almost 5000 cases of fever with muscle aches and headache were reported between February 27 and March 5, 2006. In Bangalore, there was an outbreak of Chikungunya in May 2006 with arthralgia/arthritis, rashes. So also in the neighbouring state of Andhra Pradesh. The latest outbreak in Tamilnadu, India, 20,000 cases were reported in June 2006. Earlier it was found spreading mostly in outskirts of Bangalore, but now it has started spreading in the city also.

Analysis of the recent outbreak has suggested that the increased severity of the disease may be due to a change in the genetic sequence, altering the virus' coat protein, which potentially allows it to multiply more easily in mosquito cells.
How do humans become infected with chikungunya virus?
How do humans become infected with chikungunya virus?The chikungunya virus is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with the chikungunya virus. Monkeys, and possibly other wild animals, may also serve as reservoirs of the virus. Infected mosquitoes can then spread the virus to other humans when they bite.

Aedes aegypti (the yellow fever mosquito), a household container breeder and aggressive daytime biter which is attracted to humans, is the primary vector of chikungunya virus to humans. Aedes albopictus (the Asian tiger mosquito) may also play a role in human transmission is Asia, and various forest-dwelling mosquito species in Africa have been found to be infected with the virus.
What are the symptoms?
What are the symptoms?After an incubation period of 3-12 days there is a sudden onset of flu-like symptoms including a severe headache, chills, fever (>40°C, 104°F), joint pain, nausea, vomiting and a rash involving the limbs and trunk. The joints of the extremities in particular become swollen and painful to the touch. Haemorrhage is rare and all but a few patients recover within 3-5 days. There can also be headache, conjunctival injection and slight photophobia. Some can suffer for joint pain for months. Children may display neurological symptoms.
How is it diagnosed?
How is it diagnosed?Sudden severe headache, chills, fever, joint and muscle pain are the commonest symptoms. The diagnostic tests include detection of antigens or antibodies in the blood, using ELISA (or EIA - enzyme immunoassay) or molecular techniques like polymerase chain reaction (PCR). The antibodies detected by serological assays like ELISA require an IgM capture assay to distinguish it from dengue fever.
How is it treated?
How is it treated?While supportive or palliative medical care with anti-inflammatory drugs and analgesics is available, there is no specific treatment for chikungunya. The illness is usually self-limiting and resolves with time. Symptomatic treatment is recommended after excluding other more dangerous diseases. Analgesics, antipyretics and fluid supplementation are important aspects in managing this infection. There is no vaccine currently available.

The virus can be killed by common disinfectants, moist heat and drying. The vector (a mosquito) also needs to be controlled with insecticides.
How to prevent Chikungunya?
How to prevent Chikungunya?Prevention is possible by controlling proliferation of mosquitoes in stagnant water. Water collection should be avoided by:
  • Eliminating any still water found on roofs
  • Seeing to it that water pipes are not clogged
  • Properly covering all water tanks so that mosquitoes cannot get in
  • Getting rid of any container capable of retaining water in the outdoor surroundings (used tyres, food cans, garbage, saucers under flower pots, etc)
  • Renew water in flower vases at least once a week
Other precautions:
  • Wear clothes that suitably cover arms and legs
  • Use mosquito nets and mosquito repellent products (coils, sprays, topical lotions and creams)
  • Have secure screens on windows and doors to keep mosquitoes out.
  • A person with chikungunya fever should limit their exposure to mosquito bites in order to avoid further spreading the infection, and should stay indoors or under a mosquito net.
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