Mystery behind emergence and re-emergence of Chikungunya virus


Chikungunya (CHIK) virus is a ribonucleic acid (RNA) virus with a single stranded, positive sequence RNA genome. It causes CHIK fever, a vector borne disease transmitted by mosquitoes belonging to the genus Aedes. The disease is characterized by abrupt onset of fever, chill, headache and severe joint pain. The incubation period of the virus ranges from one to12 days; the infection is always self-limiting and rarely fatal. CHIK virus originated from Africa and spread to Asia and other parts of the world. It has different genotypes and varied modes of transmission. The virus, with a history of emergence and re-emergence, is responsible for several epidemics and isolated outbreaks involving large populations in many parts of Africa and Asia as well as other regions of the world. The mystery behind the repeated re-emergence of CHIK virus is still unresolved. This is a major challenge for the medical fraternity.

Keywords: Emerging virus, epidemiology, diagnosis

How to cite this article:
Ramana K V, Prakash G K. Mystery behind emergence and re-emergence of Chikungunya virus. Ann Trop Med Public Health 2009;2:1-3


How to cite this URL:
Ramana K V, Prakash G K. Mystery behind emergence and re-emergence of Chikungunya virus. Ann Trop Med Public Health [serial online] 2009 [cited 2020 Dec 5];2:1-3. Available from:



Chikungunya (CHIK) virus belongs to the family Togovridae and genus Alpha virus. It is responsible for Chikungunya fever. Ever since the virus was first isolated, in 1953, following an outbreak in Makunde plateau bordering Tanganyika (Tanzania) and Mozambique it caused several epidemics involving numerous countries and more predominantly Africa and Asia. [1] CHIK virus is spread by the bite of mosquito Aedes aegypti. The name Chikungunya comes from Swahili, the literature of Makonde, meaning “that which bends up” referring to the contorted posture of patients afflicted with severe joint pains. [2] CHIK virus originated in Africa and spread to other regions including Asia. [3] Though the CHIK virus has originated in Africa, it exhibits different genotypes and different modes of transmission. [3] The complete nucleotide sequence of CHIK virus has been determined.

athogenecity and Clinical Features

Infected mosquitoes belonging to the genus Aedes (In Africa the species are Ae furcifer, Ae taylori, Ae luteocephalus, Ae africanus and Ae neoafricanus and in Asia the Ae aegypti and Ae albopictus (Asian tiger mosquito are vectors) infect humans through bites. Other modes of transmission include the vertical transmission of the virus from mother to child. CHIK virus is maintained in a sylvatic cycle involving wild animals, and monkeys are considered possible reservoirs of the virus. [4]

CHIK fever has an abrupt onset with fever, chills, headache and severe joint pain. The incubation period ranges from one to 12 days. Infected patients suffer from severe arthralgia, characteristically migrating and predominantly involving small joints of hands, wrists, ankles and feet with lesser involvement of larger joints.[5],[6],[7] The disease is almost self-limiting and rarely fatal. [24] Other clinical features demonstrated by infected patents include chronic joint pains and generalized myalgias. [8] In some patients cutaneous manifestations may be found as a maculopapular rash on face and trunk; photophobia and conjunctival redness may be observed in others and a few patients develop pharyngitis. [24]

Infection can be severe in elderly, newborn and immunocompromised individuals leading to meningoencephalitis. [9],[10] As evidenced by the clinical features, CHIK virus infection has to be differentially diagnosed from dengue and other viral infections. [2],[11],[12]


In Africa where the CHIK virus has originated, Aedes mosquitoes belonging to subgenera Stegomyvia (Ae africanus, Ae luteocephalus, Ae opok) and subgenera Diceromyia (Ae furcifer, Ae taylori Ae cordellieri) are responsible to maintain the virus in primates like monkeys and baboons. Initially the human infection was said to have occurred in African villages which later spread to urban areas leading to epidemics in Africa. [2],[13],[14]

The mode of transmission in Asia is primarily human to human though monkey to human infections are also reported. Bangkok in Thailand is where the virus was first isolated in 1958. It continued to spread till 1964 and infected around two million individuals. Incidentally, the virus disappeared then only to reappear in 1988. Since then the virus has led to occasional outbreaks rather than the usual epidemics. Documented reports of outbreaks of the virus are also available from Cambodia, Vietnam, Burma, Sri Lanka, Philippines, and Indonesia including India. [15]

India had its first outbreak of CHIK virus in 1963, reported by Sarkar et al. in Kolkata. [16] The data on outbreak suggests that CHIK viral infection was predominant among young children, infants and adults over 40 years with young adults showing least incidence. In 1964, an epidemic involving Vellore, Chennai and Puduchery was reported in the months of July – October.[6],[17],[18] The next incidence of CHIK viral infection was from Barsi, Sholapur districts of Maharashtra in 1973. [19]

After a quiescence of 30 years, in December 2005, the virus re-emerged as an outbreak in Rayalaseema, Hyderabad and Nalgonda districts of Andhra Pradesh. Simultaneous reports of CHIK infection emerged from Malegaon, Nasik, Beed and latur districts of Maharashtra and Gulbarga, Bidar, Bellary, Raichur, Koppal and Chitrdurge districts of Karnataka. [20] CHIK virus was also spotted in Orissa between February to March 2006.[21] Serological studies conducted in Gujarat, Rajasthan, Madhya Pradesh, Kerala suggest the presence of CHIK viral infection. [20] The 2005 December outbreak in India continues with reports of outbreaks from Andhra Pradesh, Karnataka and Maharashtra. Data shows similar clinical findings, age, sex distribution and no mortality. Unlike in previous outbreaks, cases have been reported from urban and periurban areas where entomological surveys revealed presence of high Aedes indices. In a global scenario, CHIK virus was recently reported from French reunion islands. [22]

Laboratory Diagnosis

Immunological methods

Virus specific antibodies or antigens can be demonstrated by ELISA, hemagglutination inhibition and neutralization tests. [23],[24]

Molecular methods

CHIK viral nucleic acid can be detected by polymerase chain reaction (RT-PCR, nested PCR, Taq man RT-PCR, SYBR green 1 RT-PCR), NASBA (Nucleic Acid Sequence Based Amplification), SDA (strand displacement amplification), SSR (self sustained sequence replication), RT-LAMP (real time reverse transcription loop mediated isothermal amplification assay). [25],[26],[27]


CHIK virus can be cultured in vitro in mosquito cell lines (C6/36) and mammalian cell lines. In vivo, the virus can be cultured by intracerebral inoculation of mice. [28]


There is no specific antiviral agent or vaccine against CHIK virus. Hence, prevention and control are the only methods to contain the virus infection. Active epidemiological and entomological surveillance should be carried out to identify the areas prone to infection and initiate appropriate control measures. Since the virus spreads only through Aedes mosquitoes, breeding sites must be eliminated like the open water tanks to be closed or sealed, preventing water clogging in old containers, etc.

Medical and health professionals should sensitize the community about the disease, mode of transmission, control measures and treatment availability. People should be encouraged to protect themselves from the bite of mosquitoes by using insect mosquito nets (ITN), recommend fogging with two per cent pyrethrum, use of insect repellant containing DEET (N,N, Diethyl m- toluamide), wear protective clothing etc.

The health department should encourage the participation of NGOs, community-based organizations, Medical Associations and NCC/NSS units in schools and colleges. Information on the disease must be widely disseminated in the form of mass media, news paper, TV or radio and in the form of posters, hoardings and pamphlets etc. Though the cause of emergence and re-emergence of CHIK virus is yet to be understood, studies conducted during the recent outbreaks show an increased severity of disease and genetic sequence of virus to multiply more early in mosquitoes. [10]

We should, therefore, understand that extensive research work should be carried out during and after the outbreaks to analyze the reason for repeated re-emergence of the virus. Studies to develop easy laboratory tests are required even in tertiary centers. Regional laboratories should be well equipped to diagnose CHIK virus infection during an outbreak. Molecular epidemiology of the CHIK viral infection along with active sero surveillance must be carried out.



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