12 April 2007

Imported chikungunya virus in the United Kingdom 2006

In 2006, the Health Protection Agency’s Special Pathogens Reference Unit (HPA SPRU) reported 133 cases of chikungunya infection in the United Kingdom (UK). Of those, 45 were laboratory confirmed (by polymerase chain reaction [PCR] and/or virus isolation), 30 were probable cases (clinical symptoms and serologically positive [both IgG and IgM]), 35 were classified as suspected cases (clinical symptoms, relevant travel history and IgG positive), and 23 had a past exposure (IgG positive with no clinical details or travel history, or IgG positive with known history of past exposure).

Of the total, 68 cases reported travel to the Indian Ocean islands (58 to Mauritius, six to the Seychelles, and four to Madagascar), where a large outbreak was reported earlier in 2006 [1]. Most of these cases were reported by the SPRU between 2 March and 31 August 2006. The outbreak in the Indain Ocean has since declined, with only a single case reported in December since August.

Thirty-four cases reported recent travel to India, where an outbreak began in February 2006 [2]. Nearly 1.4 million suspected cases were reported in 15 of India’s 31 states in 2006 [3], with 1,985 cases confirmed. Imported cases were not seen in the UK until May (one case); the majority of cases were reported later in the year (27 cases reported between August and November; four cases reported in December).

An outbreak of chikungunya also occurred in Sri Lanka; since mid October 2006 over 37,000 suspected cases have been reported in eleven districts [4]. Of these, 1058 samples were tested and 682 were positive for chikungunya virus. Imported cases from Sri Lanka started to be seen in the UK in November and December (three and seven cases respectively).

Cases were also reported in UK travellers who had been to Nigeria (two), Tanzania (one), Kenya (one), and Australia (one).

The outbreaks in India and Sri Lanka appear to be waning although a few cases are still being reported. In January and February 2007, there were 22 cases of chikungunya reported in UK travellers (14 in January, eight in February); 16 had travelled to Sri Lanka, two to India, and four had no country stated).

Advice to Travellers

Nearly 800,000 United Kingdom residents travelled to India in 2005, a 21% increase compared to 2004 [5]. Travellers to India and Sri Lanka, as well as to the Indian Ocean Islands, should remain aware of the risk of infection, which is transmitted by Aedes sp mosquitoes (the same mosquito that transmits dengue fever, a disease which is also prevalent in India and Sri Lanka). Aedes mosquitoes are active during daylight hours (particularly around dusk and dawn) and prevention relies on insect bite avoidance.

Further information about chikungunya can be found in the NaTHNaC clinical update of 7 February 2007 or on the HPA website at: http://www.hpa.org.uk/infections/topics_az/Chikungunya/

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References

1. NaTHNaC. Chikungunya virus – update. 21 July 2006 [online]. [Accessed 11 April 2007]. Available at: http://www.nathnac.org/pro/clinical_updates/chik_210706.htm

2. World Health Organization Epidemic and Pandemic Alert and Response (EPR) [online]. Chikungunya in India, 17 October 2006. [Accessed 19 December 2006]. Available at http://www.who.int/csr/don/2006_10_17/en/index.html.

3. National Vector Borne Disease Control Programme. Chikungunya fever situation in the country during 2006 [online] [Accessed 11 April 2007]. Government of India Ministry of Health and Family Welfare. Available at http://www.nvbdcp.gov.in/Chikun-cases.html.

4. The Centre for Prevention and Control of Communicable Diseases, Ministry of Health, Sri Lanka. Investigation of the Outbreak of Chikungunya Fever – 2006/7 Sri Lanka [online] [accessed 11 April 2007]. Available at http://www.epid.gov.lk/pdf/chikungunya/OBOFCHIGYA.pdf.

5. Office for National Statistics. The International Passenger Survey, Travelpac dataset 2005 [online]. London: ONS, 2006. Available at http://www.statistics.gov.uk/statbase/Product.asp?vlnk=14013