Chikungunya fever-Perceptive of current epidemic-2007

What is Chikungunya fever?

Chikungunya fever is an acute debilitating viral disease transmitted to humans by the bite of infected mosquitoes mainly Aedes aegypti or Aedes albopictus (the Asian tiger mosquito). Chikungunya virus, RNA virus of the genus Alpha virus and the family Togaviridae was first isolated from the blood of a febrile patient and also from the mosquitoes in 1952-53 in Tanzania, Africa .The name is derived from the Swahili word meaning "that which bends up" in reference to the stooped posture developed as a result of the arthritic symptoms of the disease. The basic clinical presentation is a person with good health goes into a state of illhealth with fever and arthralgia in smaller joints initially.
Origin and History
The Chikungunya fever is not new to the world. The virus first appeared in India in1963 at Calcutta, Madras and other areas along with and complicated with hemorrhagic manifestations. Retrospective studies showed that historical epidemic started in Indonesia (1779) in India (1824) and United states (1827) as fever, rash and arthralgia. Chikungunya fever displays interesting epidemiological profile-major epidemics appear, disappear and reappear cyclically, usually with an interval of 7-8 years and sometimes as long as 20 years. It occurred at irregular intervals along the east coast of India till 1973.But it was present in various parts of Asia till 1982. ( Sri lanka 1969,Vietnam and Myanmar 1975, Indonesia 1982) After a long period of quiescence the present state of epidemics of Chikungunya fever had appeared in Indonesia in 1999 . Recent epidemic originated in Indian ocean islands and spread to various parts of India ( Andra Pradesh, Karnataka, Maharashtra in 2005).Kerala started experiencing Chikungunya outbreaks since 2006 and continuing in 2007.
Clinical features
The incubation period (time from virus entry to illness) can be 2-12 days, but is usually 3-7 days. “Silent” Chikungunya virus infections (infections without illness) do occur, but how commonly this happens is not yet known. The disease resembles Dengue fever and is characterized by fever, headache, fatigue, nausea, vomiting, muscle pain, rash, Photophobia and joint pain. The prolonged /persistent joint pain is not seen in Dengue fever. Co occurrence of Dengue fever was reported from some areas leading to complications. Acute Chikungunya fever typically lasts a few days to a couple of weeks, but as with other arboviral fevers, some patients have prolonged fatigue lasting several weeks. Some patients have reported incapacitating joint pain, or arthritis which may last for weeks or months.
Epidemiology
Chikungunya virus fever is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on a person infected with Chikungunya virus. Monkeys, and possibly other wild animals, may also serve as reservoirs of the virus. Aedes aegypti, 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 in Asia. Hemorrhagic manifestations were common when the disease first appeared in 1963 but have been extremely rare afterwards.
Importance of early diagnosis
After virus entry there is high level of viremia initially and virus can be isolated from blood up to 4 days after onset. Dissemination occurs as virus is released from cells that lyse. Antibodies appear by 5-7 days. Virus is eliminated by immune system but arthritis may persist for 3-4 months.
Diagnosis remains as a challenge in acute outbreak of infection always in need of the assistance of a Virology Reference laboratory. Virus isolation by blood culture takes at least 1 week and possible only in the first 4 days of onset as the virus are cleared from blood when antibodies appear. With advanced techniques like RT PCR also possible only in the first 4 days of disease. Presently the diagnosis is done in the routine diagnostic laboratories by detection of specific Ig M antibodies by ELISA or Immunochromatographic methods.

Treatment
No specific antiviral drugs for chikungunya fever are available. Treatment is symptomatic--rest, fluids, and ibuprofen, naproxen, acetaminophen, or paracetamol may relieve symptoms of fever and aching. Self medication and empirical prescription with aspirin should be avoided as it can lead to hemorrhage or Reye’s syndrome. “In unresolved arthritis refractory to paracetamol and nonsteroidal anti-inflammatory drugs, chloroquine phosphate (250 mg/day) has given promising results.” Chikungunya virus infection is not fatal but deaths may be due to other underlying or associated diseases or infections
Prevention
No vaccine is available. The best way to prevent is to avoid mosquito bites. As infected persons are the source of infection should limit further exposure to mosquito bites, stay indoors and under a mosquito net.Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels, coconut shells etc.Usually Aedes mosquito’s life cycle that is from egg to adult is 7 days. So weekly once or twice spraying of insecticides to kill the larvae in the possible breeding sites and fogging regularly to kill mosquitoes are very essential control measures. During epidemic, other measures to be taken are wear long sleeve dress and pants, use insect repellent, have secure screens on windows and doors to keep mosquitoes out.
The virus can migrate from endemic area to non endemic area through infected persons so screening of people at the various migratory sites by fever clinic is also helpful in the control of disease.
Screening for viral antibodies, cleaning of premises and destruction of breeding sites of mosquitoes should be continued,otherwise Chikungunya virus will remerge.
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My email address: drsathiavathy@gmail.com
Dr. K.A. Sathiavathy. M.D (Micro)
Professor of Microbiology,
Jubilee Mission Medical College & RI,
Trichur, Kerala, India

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