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Causative Agent

Chikungunya virus

Incubation Period

Average 3 – 7 days (range 2 – 12 days)

Infectious Period

From up to 2 days before illness onset to 5 days after illness onset.


Chikungunya means “that which bends up” in the East African/Mozambique Makonde language. Regular outbreaks in East and West Africa, Indian Ocean islands, Asia, and more recently southern Europe.

In Singapore, the first outbreak of chikungunya fever was reported in Jan 2008 in Little India where Aedes aegypti was the vector implicated in transmission. A few local cases resurfaced in May and June 2008 in suburban residential areas. A sharp increase in local cases occurred again in July 2008 in rural industrial and farming areas where Aedes albopictus was the predominant vector, and coincided with the rise in imported from Malaysia. A total of 718 laboratory confirmed cases (181 imported) were reported in 2008. Following aggressive vector control measures, cases subsided rapidly in Feb 2009 with 341 cases (66 imported) reported in 2009. In the first 9 months of 2010, 7 local and 18 imported were reported.The incidence rate among indigenous cases was highest in the 35-44 year age group with a male to female ratio of 3.9:1.

Asymptomatic infections do occur but how common this is remains to be determined. Infection is thought to result in lifelong immunity. In older reports chikungunya fever has been described as a self-limited illness, although severe complications and death have been reported in the more recent outbreaks. Pregnant women can be infected with chikungunya virus. Most infections will not be transmitted to the foetus. There are, however, rare reports of first trimester abortions occuring after chikungunya infection. There is no evidence that the virus can be transmitted through breast milk.

  • Fever – high with acute onset; maybe biphasic. Usually lasts only 3-4 days.
  • Joint pain, with or without swelling or erythema, is a prominent distinguishing feature
    • Initial severe eruptive polyarthritis/arthralgia with classical history of painful walking. Typically followed by protracted peripheral arthropathy that can last for months
    • Commonly affects the knees, ankles and wrists; also the small joints of hands and feet
  • Rash
    • Maculopapular or mobiliform (older children/adults); may be pruritic
    • Vesiculobullous eruptions described in infants
    • Typically on trunk and limbs
    • Haemorrhagic manifestations uncommon
  • Headache
  • Conjunctival injection
  • Nausea, vomiting
  • Fatigue (may last for weeks)

Especially reported in more recent outbreaks. More common in those aged above 65 years and with underlying medical conditions.

  • Respiratory failure
  • Bleeding
  • Meningoencephalitis
  • Acute hepatitis
  • Ocular manifestations (iridocyclitis, retinitis and episcleritis)

A wide spectrum of viral, bacterial and parasitic infections mimic chikungunya in the febrile phase including malaria, dengue (less persistent joint pains) and other viral illnesses (e.g. Ross River virus, acute HIV, rubella, measles and EBV). Non- infective aetiologies, such as autoimmune diseases, should also be considered.

  • FBC: lymphopaenia, thrombocytopaenia.
  • LFTs: mild to moderate elevated transaminases (usually AST > ALT).
  • Serology: Positive chikungunya IgM on acute serum sample. IgM antibodies appear on approximately the fifth day of illness and last for two months. A 4- fold rise in titres of a pair of acute and convalescent sera is confirmatory.
  • PCR for chikungunya virus within five days of onset may give a more rapid diagnosis.

A legally notifiable disease in Singapore. Notify Ministry of Health (Form MD 131 or electronically via CD-LENS) not later than 24 hours from the time of diagnosis.

The residential address and place of work/school of cases should also be given.

  • Supportive
  • Paracetamol for fever, aches and pains. Non-steroidal anti-inflammatory drugs may be considered for joint pains.
  • Fluids and rest

The National Environment Agency carries out entomological investigation around the residence and/or workplace of notified cases, particularly if these cases form a cluster where they are within 200 meters of each other. They also carry out epidemic vector control measures in outbreak areas and areas of high Aedes population identified on routine surveillance; and intensive public education to remove Aedes breeding habitats.


  1. Centers for Disease Control and Prevention. Chikungunya Available at Accessed Sept 2010.
  2. Ng LC, Tan LK, Tan CH et al. Entomologic and virologic investigation of chikungunya, Singapore. Emerg Infect Dis 2009; 15:1243-9.
  3. Leo YS, Chow ALP, Tan LK et al. Chikungunya outbreak, Singapore, 2008. Emerg Infect Dis  2009; 15:836-7.
  4. Ng KW, Chow A, Win MK et al. Clinical features and epidemiology of chikungunya in Singapore. Singapore Med J 2009; 50:785-90.
  5. Ministry of Health. Risk factors for transmission of chikungunya virus infection in Singapore, 2008. Epidemiol News Bull 2009;35:1-6.

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