Chikungunya (chick-un-GUNE-ya) is an arthropodborne virus transmitted to humans via a mosquito bite. Transmission of the disease is known to occur in regions within India, Africa, Southeast Asia, the Philippines, and the Caribbean. However, since 2000, infections have occurred worldwide as travelers have contracted chikungunya from infected mosquitoes while traveling through endemic regions (areas where the disease exists normally), and then imported the disease when they traveled home.
Infection usually results in a range of symptoms including fever, aches, joint pains, nausea, vomiting, and chills. However, a full recovery is common following treatment involving rest, fluids, and drugs for fever or joint pains. There have been a large number of outbreaks between the years of 2004 and 2007, particularly inIndia and groups of islands in the Indian Ocean. Because of these outbreaks, the World Health Organization considers chikungunya an important re-emergent disease (a disease capable of causing large outbreaks after a period of relatively few occurrences).
There is no vaccine available to protect against infection with the chikungunya virus, therefore, the best prevention method is avoidance of mosquitoes. This is achieved by using insect repellants, wearing long-sleeved clothing, using mosquito nets, and removing stagnant water bodies where mosquitoes breed.
WORDS TO KNOW
VECTOR: Any agent, living or otherwise, that carries and transmits parasites and diseases. Also, an organism or chemical used to transport a gene into a new host cell.
Chikungunya virus infection was first described during the 1950s by scientists Marion Robinson and W.H.R. Lumsden. The first known outbreak occurred during 1952 in Africa, and the first outbreak in India was in 1963 in Calcutta.
Infection is transmitted to humans via a bite from mosquitoes in the genus Aedes. These mosquitoes are also responsible for the transmission of dengue and yellow fever. Mosquitoes pick up the infection when they feed on infected people or non-human primates. This virus is from the family Togoviridae and the genus Alphavirus. Infection is not thought to be transmitted directly from person to person.
Chikungunya manifests itself in humans one to 12 days (usually about a week) after being bitten by an infected mosquito. Most cases result in a range of symptoms, although there have been some asymptomatic cases. The most common symptoms are: fever, headache, joint pain, swelling of joints, arthritis of the joints, chills, nausea, and vomiting. A rash may also occur, and in rare cases, bleeding and hemorrhaging result. Acute fever usually lasts from a few days to two weeks, and some people with chikungunya experience prolonged fatigue. The symptoms of chikungunya are similar to dengue fever, and as a result, the disease is sometimes misdiagnosed. Life-long immunity is thought to occur following chikungunya infection.
Chikungunya first appeared in Africa in 1952 and was first discovered in India ten years later. The virus is distributed around Africa and Asia. Outbreaks have been reported in India, Central and South Africa, Africa, Southeast Asia, the Philippines, and the Caribbean.
In 2005, there was a reemergence of chikungunya in India with 180,000 cases reported between 2005 and 2007. In early 2005, an outbreak occurred in the Comoro Islands. Since this outbreak, other islands in the Indian Ocean have reported infections. On the island of Réunion, chikungunya infection was first identified in March 2005, with 150,000 cases identified before February 2006. Among the other islands in the Indian Ocean, 300,000 suspected cases were reported before May 2006. The chikungunya outbreak in this region constitutes the largest known outbreak since scientists began tracking the disease.
Transmission of chikungunya has not yet been found to occur in Europe or other non-endemic areas. However, there are an increasing number of travelers being infected while in regions with chikungunya outbreaks and then returning to non-infected regions. Between 2005 and 2006, the Centers for Disease control and Prevention (CDC) diagnosed 12 travelers from the United States infected with chikungunya after traveling to known infected areas.
Treatment of chikungunya is aimed at relieving symptoms. No vaccine or specific antiviral treatment is available. The most common treatments for symptoms include rest, fluids, and anti-inflammatory/analgesic drugs such as ibuprofen, naproxen, acetaminophen, or paracetamol. These treatments help relieve fever, aches, joint pains, and arthritis. In most cases, people recover fully from chikungunya, often in a few days. However, in rare cases, joint pain can persist, or prolonged fatigue may be experienced. Death is unlikely, although there are a few reported deaths related to bleeding from this infection. Some deaths appear to be the result of using aspirin to treat symptoms, which may be linked with bleeding in persons with chikungunya.
As this infection is transmitted via mosquitoes, the best prevention method is to avoid the bite of infected mosquitoes. This can be achieved by eliminating mosquito breeding grounds, such as stagnant water bodies; using insect repellants on the body and clothing; using mosquito nets; and wearing long-sleeved clothing. In addition, to prevent infection from being spread to more mosquitoes, the above prevention methods should be used by infected people as well.
Although chikungunya transmission is confined to endemic countries, infection can occur worldwide as travelers to infected regions become infected and return to their home countries. This has a potential impact on the distribution of this disease. The distribution of one chikungunya disease vector, the mosquito Aedes aegypti, is almost worldwide. Therefore, the risk for large geographic expansion of endemic areas of the disease is possible. Mosquitoes from non-infected regions could become infected by feeding on infected travelers, or could be imported within shipping containers, thus potentially spreading chikungunya to previously uninfected regions.
Distinguishing between chikungunya and dengue fever is sometimes difficult, as they have similar symptoms and are transmitted via the same vector. Therefore, the occurrence of chikungunya may be misrepresented due to misdiagnosis. The CDC suggests that the possibility that cases of chikungunya have been misdiagnosed as dengue fever could potentially mean that the number of chikungunya cases is higher than previously assumed.
French authorities received media criticism for a perceived slow response to the Réunion Island (an overseas department of France) outbreak in 2005. By February 2006, the French government took measures to eliminate mosquito breeding grounds on the island, and formed a task force to study re-emerging infectious diseases, especially chikungunya. Researchers in France are currently working to test a preliminary vaccine developed for chikungunya in the 1980s by United States Army scientists.
IN CONTEXT: REAL-WORLD QUESTIONS
The CDC states, “The best way to avoid CHIKV infection is to prevent mosquito bites in impacted areas. As of February 2007, there is no vaccine or preventive drug. Prevention tips are similar to those for dengue fever or West Nile virus:
- Use insect repellent containing an DEET or another EPA-registered active ingredient on exposed skin. Always follow the directions on the package.
- Wear long sleeves and pants (ideally treat clothes with permethrin or another repellent).
- Have secure screens on windows and doors to keep mosquitoes out.
- Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in birdbaths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.
- A person with chikungunya fever or dengue should limit their exposure to mosquitoes in order to avoid spreading the infection to more mosquitoes.”
SOURCE: Centers for Disease Control and Prevention (CDC)
Hochedez P., S. Jaureguiberry, M. Debruyne, P. Bossi, P. Hausfater, G. Brucker, F. Bricaire, and E. Caumes. “Chikungunya Infection in Travelers.” Emerging Infectious Diseases. vol. 12, no. 10 (2006): 1565–1567.
Centers for Disease Control and Prevention (CDC). “Chikungunya Fever.” Jan. 16, 2006 <http://www.cdc.gov/ncidod/dvbid/Chikungunya/index.htm> (accessed February 8, 2007).
Centers for Disease Control and Prevention (CDC). “Chikungunya Fever Diagnosed Among International Travelers—United States, 2005–2006.” Sep. 29, 2006 <http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5538a2.htm> (accessed February 8, 2007).
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