Chikungunya virus (CHIKV) is an insect-borne virus, of the genus, Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. There have been recent outbreaks of CHIKV associated with severe morbidity. CHIKV causes an illness with symptoms similar to dengue fever. CHIKV manifests itself with a prolonged arthralgic disease that affects the joints of the extremities. The acute febrile phase of the illness lasts only two to five days. The pain associated with CHIKV infection of the joints persists for weeks or months.
Signs and symptoms
The incubation period of Chikungunya disease is from two to four days. Symptoms of the disease include a fever up to 39 ℃ (102.2 ℉), a petechial or maculopapular rash of the trunk and occasionally the limbs, and arthralgia or arthritis affecting multiple joints. Other nonspecific symptoms can include headache, conjunctival injection, and slight photophobia. Typically, the fever lasts for two days and then ends abruptly. However, other symptoms, namely joint pain, intense headache, insomnia and an extreme degree of prostration last for a variable period; usually for about 5 to 7 days. Patients have complained of joint pains for much longer time periods depending on their age.
Common laboratory tests for chikungunya include RT-PCR, virus isolation, and serological tests.
- Virus isolation provides the most definitive diganosis but takes 1-2 weeks for completion and must be carried out in Biosafety level 3 laboratories. The technique involves exposing specific cell lines to samples from whole blood and identifying chikungunya virus-specific responses.
- RT-PCR using nested primer pairs to amplify several Chikungunya-specific genes from whole blood. Results can be determined in 1-2 days.
- Serological diagnosis requires a larger amount of blood than the other methods and uses an ELISA assay to measure Chikungunya-specific IgM levels. Results require 2-3 days and false positives can occur with infection via other related viruses such as O'nyong'nyong virus and Semliki Forest Virus.
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Chikungunya virus is indigenous to tropical Africa and Asia, where it is transmitted to humans by the bite of infected mosquitoes, usually of the genus Aedes. CHIK fever epidemics are sustained by human-mosquito-human transmission. The word "chikungunya" is thought to derive from description in local dialect of the contorted posture of patients afflicted with the severe joint pain associated with this disease. The main virus reservoirs are monkeys, but other species can also be affected, including humans.
The most effective means of prevention are those that protect against any contact with the disease-carrying mosquitoes. These include using insect repellents with substances like DEET (N,N-Diethyl-meta-toluamide; also known as N,N'-Diethyl-3-methylbenzamide or NNDB), icaridin (also known as picaridin and KBR3023), PMD (p-menthane-3,8-diol, a substance derived from the lemon eucalyptus tree), or IR3535. Wearing bite-proof long sleeves and trousers (pants) also offers protection. In addition, garments can be treated with pyrethroids, a class of insecticides that often has repellent properties. Vaporized pyrethroids (for example in mosquito coils) are also insect repellents. Securing screens on windows and doors will help to keep mosquitoes out of the house. In the case of the day active Aedes aegypti and Aedes albopictus, however, this will only have a limited effect, since many contacts between the vector and the host occur outside. Thus, mosquito control is especially important.
There are no specific treatments for Chikungunya. There is no vaccine currently available. A Phase II vaccine trial, sponsored by the US Government and published in the American Journal of Tropical Medicine and Hygiene in 2000, used a live, attenuated virus, developing viral resistance in 98% of those tested after 28 days and 85% still showed resistance after one year.
Chloroquine is gaining ground as a possible treatment for the symptoms associated with chikungunya, and as an antiviral agent to combat the Chikungunya virus. A University of Malaya study found that for arthritis-like symptoms that are not relieved by aspirin and non-steroidal anti-inflammatory drugs (NSAID), chloroquine phosphate (250 mg/day) has given promising results. Research by an Italian scientist, Andrea Savarino, and his colleagues together with a French government press release in March 2006 have added more credence to the claim that chloroquine might be effective in treating chikungunya. Unpublished studies in cell culture and monkeys show no effect of chloroquine treatment on reduction of chikungunya disease. The fact sheet on Chikungunya advises against using aspirin, ibuprofen, naproxen and other NSAIDs that are recommended for arthritic pain and fever.
DNA vaccination is a technique for protecting an organism against disease by injecting it with genetically engineered DNA to produce an immunological response. Nucleic acid vaccines are still experimental, and have been applied to a number of viral, bacterial and parasitic models of disease, as well as to several tumour models. DNA vaccines have a number of advantages over conventional vaccines, including the ability to induce a wider range of immune response types.A recent study report that a novel consensus-based approach to vaccine design for Chikungunya virus, employing a DNA vaccine strategy. The vaccine cassette was designed based on CHIKV Capsid and Envelope specific consensus sequences with several modifications, including codon optimization, RNA optimization, the addition of a Kozak sequence, and a substituted immunoglobulin E leader sequence. Analysis of cellular immune responses, including epitope mapping, demonstrates that these constructs induces both potent and broad cellular immunity in mice. In addition, antibody ELISAs demonstrate that these synthetic immunogens are capable of inducing high titer antibodies capable of recognizing native antigen. Taken together, these results support further study of the use of consensus CHIKV antigens in a potential vaccine cocktail.
|Please help improve this section by expanding it. Further information might be found on the talk page or at requests for expansion. (March 2008)|
Recovery from the disease varies by age. Younger patients recover within 5 to 15 days; middle-aged patients recover in 1 to 2.5 months. Recovery is longer for the elderly. The severity of the disease as well as its duration is less in younger patients and pregnant women. In pregnant women, no untoward effects are noticed after the infection.
Pedal oedema (swelling of legs) is observed in many patients, the cause of which remains obscure as it is not related to any cardiovascular, renal or hepatic abnormalities.
Chikungunya virus is an alphavirus closely related to the O'nyong'nyong virus, the Ross River virus in Australia, and the viruses that cause eastern equine encephalitis and western equine encephalitis.
Chikungunya is generally spread through bites from Aedes aegypti mosquitoes, but recent research by the Pasteur Institute in Paris has suggested that chikungunya virus strains in the 2005-2006 Reunion Island outbreak incurred a mutation that facilitated transmission by Aedes albopictus (Tiger mosquito). Concurrent studies by arbovirologists at the University of Texas Medical Branch in Galveston Texas confirmed definitively that enhanced chikungunya virus infection of Aedes albopictus was caused by a point mutation in one of the viral envelope genes (E1).. Enhanced transmission of chikungunya virus by Aedes albopictus could mean an increased risk for chikungunya outbreaks in other areas where the Asian tiger mosquito is present. A recent epidemic in Italy was likely perpetuated by Aedes albopictus.
Since its discovery in Tanganyika, Africa in 1952, chikungunya virus outbreaks have occurred occasionally in Africa, South Asia, and Southeast Asia, but recent outbreaks have spread the disease over a wider range.
- The first outbreak in India was in 1963 in Kolkata (Calcutta).
- An outbreak of chikungunya was also discovered in Port Klang in Malaysia in 1999 affecting 27 people
- There was an outbreak in Italy late 2007, with 160 cases, and suspects about some human-to-human contaminations.
- 2005-2006, 237 deaths were associated with chikungunya on Réunion island and one third of the island's population were infected. There was also a widespread outbreak in India, primarily in Tamil Nadu, Karnataka, Kerala, and Andhra Pradesh.
- After flooding and heavy rains in Rajasthan, India in August 2006, thousands of cases were detected in Rajsamand, Bhilwara, Udaipur, and Chittorgarh districts, and also in adjoining regions of Gujarat and Madhya Pradesh, and in the neighbouring country of Sri Lanka.
- In the southern Indian state of Kerala, 125 deaths were attributed to Chikungunya with the majority of the casualties reported in the district of Alapuzha, primarily in Cherthala.
- In December 2006, there were outbreaks of 3,500 confirmed cases in the Maldives, and over 60,000 cases in Sri Lanka, with over 80 deaths.
- In October 2006, more than a dozen cases of chikungunya were reported in Pakistan.
- During June 2007 in Pathanamthitta, Kottayam and Alappuzha districts of South Kerala, India claimed more than 50 lives, though no mortality has definitively been linked to chikungunya virus. It is confirmed officially that there are 7000 confirmed Chikungunya patients in these areas. Unofficial reports suggest that more than one hundred thousand are suffering from symptoms of chikungunya.
- In early 2007, chikungunya spread from Kerala and Tamil Nadu to Sri Lanka and many people were infected.
- The European Network for Diagnostics of "Imported" Viral Diseases claims that new phylogenetic variants of the virus have been identified on Réunion.
- In August/September 2007, at least 200 people were infected in Italy's northern Ravenna region, resulting in one death.
- In January 2008, at least 8 people have been diagnosed with Chikungunya in Melbourne, Australia. There are concerns that the disease could spread to other regions of Australia
- On January 24, 2008, 10 were infected in the first outbreak in Singapore. A high-level public health administrator was given legal powers to detain and isolate any chikungunya cases
- In May 2008, Deccan Herald reported outbreak of chikungunya in Sullia, Puttur, Kasaragod Taluks (Taluk~County) of southern India. At least 1600 suspected cases in Sullia.">
- More than 200,000 people were affected by chikungunya in South Kanara region and till today 34 deaths were reported. Though government officials say that deaths were not due to chikungunya, all were suffering from this during their terminal stage and they did not had any other diseases except in few cases.
- On July 26, 2008, The West Australian newspaper reported that there had been 15 cases of the disease notified in Western Australia in the preceding two years, and that the virus had become established in local mosquito populations. 
- As of September 13, 2008, 1,975 cases had been reported in Malaysia, over half of which occurred in the state of Johor.  Prior to 2008, small outbreaks involving not more than 40 people had occurred occasionally since 1999, mostly involving immigrant workers from India or Malaysians who had visited India.