NAME: Chikungunya virus
CHARACTERISTICS: A member of the Togaviridae familyFootnote 4 Footnote 10 Footnote 11, and Alphavirus genusFootnote 10 Footnote 11, belonging to the Semliki Forest serological complexFootnote 1 Footnote 11. CHIKV is a spherical enveloped virion that measures 60 to 70 nm in diameterFootnote 1 Footnote 11, and contains a single-stranded, positive-sense RNA genomeFootnote 11.
PATHOGENICITY/TOXICITY: Translated from the African dialect of Swahili or Makonde, chikungunya means, “that which bends up”Footnote 1 Footnote 2 Footnote 12, “what bends”Footnote 10, or “to walk bent over”Footnote 13, and refers to the effect of the incapacitating arthralgia experienced by patients with CHIKV feverFootnote 1. CHIKV infection has an abrupt onset, characterised by fever, and severe arthralgiaFootnote 2 Footnote 13, which is seen in 70% of casesFootnote 1. The fever rises quickly, often reaching 39 to 40 °C and is accompanied by intermittent shaking chillsFootnote 2. The arthralgias are polyarticular, migratory and predominantly affect the small joints of the hands, wrists, ankles, and feetFootnote 2. Cutaneous manifestations are typical with many patients presenting a flush over the face and trunk. This is usually followed by a maculopapular rash, involving most commonly the trunk, and limbs, but the face, palms and soles can also show lesionsFootnote 2. Other symptoms of CHIKV include myalgia, nausea, vomiting, headaches, nasal discharge, conjunctivitis, retrobulbar pain, photophobia, and lymphadenopathyFootnote 10. Haemorrhagic manifestations (petechiae, purpura, bleeding gums, nosebleeds, haematemesis, and melena)Footnote 1 have been documented, but only in AsiaFootnote 10. The average fatality rate is 0.4% (2.8% in children and 1.6% in elderly people)Footnote 10.
EPIDEMIOLOGY: CHIKV was first recognised in Tanzania (formerly Tanganyika) in 1953 during an epidemic of dengue-like illnessFootnote 12. Between the 1960s and 1990s, the virus was isolated repeatedly from numerous countries in Central and Southern Africa, including Sudan, Uganda, Democratic Republic of Congo, the Central African Republic, Malawi, Zimbabwe, Kenya, and South AfricaFootnote 3. CHIKV has also been isolated in Western African countries, including Senegal, Benin, the Republic of Guinea, Côte d’Ivoire and NigeriaFootnote 3.
In Southeast Asia, frequent outbreaks were reported from the 1960s through to 2003 in India, Malaysia, Indonesia, Cambodia, Vietnam, Myanmar, Pakistan, and ThailandFootnote 3. Indeed, numerous cities, including Bangkok and Calcutta have been identified as particularly active sites of transmission and diseaseFootnote 3.
Beginning in 1986, CHIKV outbreaks resurged with major clusters documented in Senegal (1986, 1996, and 1997), Côte d’Ivoire (1996 and1997), Democratic Republic of Congo (1998-2000), Indonesia (2003), Kenya (2004), Comoros (2005), the Seychelles, Mauritius, Madagascar and Réunion islands (2005-2006), and India (2006 and 2007)Footnote 3.
Cases have also been reported in Europe (United Kingdom, Belgium, Germany, Czech Republic, Norway, Italy, Spain and France), Hong Kong, Canada, Taiwan, Sri Lanka and United States; however, these were directly associated with the return of tourists from India and the affected islands of the Indian OceanFootnote 3 Footnote 13.
There are 2 epidemiological transmission cycles of CHIK fever: a sylvatic cycle, occurring primarily in Africa mainly between wild primates and arboreal Aedes mosquitoesFootnote 2 Footnote 3, where humans are accidental hosts; and an urban human-mosquito-human transmission cycle that typically occurs in cities in AsiaFootnote 2.
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: CHIKV is transmitted to humans from infected non-human primates and other humans by the bite of Aedes mosquitoesFootnote 1. Evidence exists that CHIKV can also be passed from an infected mother to a developing foetusFootnote 2 Footnote 13. Furthermore, inhalation of aerosolised CHIKV in a laboratory setting may lead to CHIKV infectionFootnote 14.
COMMUNICABIILTY: Person-to-person transmission is only thought to occur in utero between a mother and her foetusFootnote 2.
RESERVOIR: Humans serve as the reservoir for CHIKV during epidemic periodsFootnote 2 Footnote 11 Footnote 13. Outside these periods the main reservoirs are monkeysFootnote 10 Footnote 11 Footnote 13, rodentsFootnote 10 Footnote 13, batsFootnote 10, and birdsFootnote 10 Footnote 11 Footnote 13.
VECTORS: MosquitoesFootnote 1-3 Footnote 7 Footnote 10 Footnote 11 Footnote 13. In Asia and the Indian Ocean region, the main vectors are Aedes aegyptiFootnote 2 Footnote 10 Footnote 11 and Aedes albopictusFootnote 2 Footnote 11. A larger range of Aedes species transmit CHIKV in Africa, including Aedes furciferFootnote 2 Footnote 10 Footnote 11 Aedes tayloriFootnote 2, Aedes vittatus, Aedes fulgensFootnote 11, Aedes luteocephalusFootnote 2 Footnote 11, Aedes dalzieli, Aedes vigilax, Aedes camptorhynchitesFootnote 11, Aedes africanusFootnote 2 Footnote 10, and Aedes neoafricanusFootnote 2.
DRUG SUSCEPTIBILITY: No antivirals are currently available. Under experimental conditions, interferon-α2b, glycyrrhizin, 6-azauridine and ribavirin have all been shown to reduce CHIKV virus yield in a concentration dependent manner in vitroFootnote 4. Moreover there is a synergistic efficacy between interferon-α and ribavirin against CHIKV in vitroFootnote 4.
SUSCEPTIBILITY TO DISINFECTANTS: No information specific to CHIKV; however, most lipid enveloped viruses are sensitive to 70% (v/v) ethanol, sodium hypochlorite, formaldehyde, glutaraldehyde, phenolics, iodophors, and quaternary ammonium compoundsFootnote 15.
PHYSICAL INACTIVATION: Inactivated by desiccation and temperatures above 58°CFootnote 11.
SURVIVAL OUTSIDE HOST: Unknown.
SURVEILLANCE: Monitor for symptomsFootnote 2. Confirmation is via detection of CHIKV in blood samples via ELISAFootnote 6, RT-PCRFootnote 16, real time RT-PCRFootnote 5, indirect immunofluorescenceFootnote 6, viral cultureFootnote 1 Footnote 11, neutralization assaysFootnote 2 Footnote 17, and/or haemagglutinin inhibition assaysFootnote 2.
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Treatments available are for symptoms only and include antipyreticFootnote 1 and anti-inflammatory drugsFootnote 1 Footnote 11 such as diclofenacFootnote 10. The use of steroids and aspirin should be avoidedFootnote 10 Footnote 11. Movement and mild exercise tend to improve stiffness in the jointsFootnote 2.
IMMUNIZATION: A commercial vaccine does not existFootnote 2 Footnote 10, although some candidate vaccines have been tested on monkeysFootnote 8 and humans (phase II)Footnote 9, and a phase III trial of a candidate vaccine is in preparationFootnote 11.
PRIMARY HAZARDS: Inhalation of CHIKV containing aerosolsFootnote 14.
SPECIAL HAZARDS: Exposure to infected insects whilst performing CHIKV isolations in endemic areasFootnote 17.
RISK GROUP CLASSIFICATION: Risk Group 3Footnote 18.
CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infectious or potentially infectious material.
PROTECTIVE CLOTHING: Personnel entering the laboratory should remove street clothing and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashesFootnote 19.
OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) or other appropriate primary containment device in combination with personal protective equipment. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are unloaded in a biological safety cabinetFootnote 19. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities.
SPILLS: Allow aerosols to settle and, while wearing protective clothing, gently cover the spill with paper towels and apply suitable disinfectant, starting at the perimeter, working inwards towards the centre. Allow sufficient contact time before clean upFootnote 19.
DISPOSAL: Decontaminate all materials for disposal by steam sterilisation, chemical disinfection, and/or incinerationFootnote 19.
STORAGE: In sealed, leak-proof containers that are appropriately labelled and locked in a Containment Level 3 laboratoryFootnote 19.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: August 2010.
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2010