25 May 2006

Imported cases of chikungunya virus

Following the NaTHNaC clinical update of 24 April 2006 on chikungunya virus (CHIKV), there has been an increase in the number of cases of chikungunya imported into the United Kingdom from islands in the Indian Ocean [1]. From 1 January 2006 to 15 May 2006 48 samples have tested positive for CHIKV infection. Testing was performed by the Health Protection Agency’s (HPA) Special Pathogens Reference Unit. Of these 48 samples, nine have been additionally confirmed by developmental PCR and/or virus isolation; the remaining samples were from suspect cases with serological evidence (presence of IgG antibodies) of CHIKV infection. In 2005, 19 suspect cases were identified and an average of six suspect cases have been identified each year between 1999 and 2004.

Where travel history was available, the majority of cases since 1999 reported recent travel to Africa or Asia. Of the 19 positive samples identified in 2005, 11 were from UK marines who had acquired chikungunya on exercise in Senegal. In 2006, samples were from travellers to Mauritius (32 samples), Seychelles (five), Madagascar (four), Africa unspecified (three), and the Antipodes (one). Five samples had no travel history.

The increase in 2006 in the number of positive cases reflects an increased awareness of the infection by clinicians seeing returning travellers, and also by travellers who have been to the islands of the Indian Ocean, where large outbreaks have been occurring in recent months [2]. Cases associated with travel to the Indian Ocean islands have also been imported to other European countries such as France, Germany, Belgium, Czech Republic, and Norway [3].

The outbreaks in the islands of the Indian Ocean appear to be declining [4], however, cases of CHIKV have been increasing in India particularly in the states of Karnataka, Maharastra, and Andra Pradesh [5]. The latest reported case numbers are available in the Table. Cases have also been identified in Madagascar and the Comoros Islands but no specific data for these countries is currently available [4].

Table 1. Latest reported case numbers of chikungunya in the Indian Ocean islands.

Country	No of cases	Dates
Reunion [4]	258,000†	Mar 05 - 14 May 06
Mayotte [4]	6,346	1 Jan 06 - 7 May 06
Mauritius [6]	10,812	5 Feb 06 - 19 Apr 06
Seychelles [7]	5,461	1 Jan 06 - 10 Mar 06
India [5]	100,000	1 Jan 06 - 30 Apr 06

† Cases estimated by mathematical modelling

Recommendations for Travellers

Although the outbreaks in the Indian Ocean are declining, the risk to non-immune travellers to chikungunya-endemic areas may still exist for some time. Mauritius and the Seychelles are popular holiday destinations for British travellers, with around 7,000 tourists per month [8] and so travellers must protect themselves against mosquito bites particularly around dawn and dusk. Further information can be found on the NaTHNaC insect bite avoidance information sheet.

Health professionals who suspect chikungunya in a returning traveller should send appropriate serum samples (paired if possible and with a detailed travel history) to the HPA Special Pathogens Reference Unit for investigation. More information about this is available at http://www.hpa.org.uk/srmd/other_ref_labs/spru.htm.  

References

1. HPA. Chikungunya: increase in imported cases. Commun Dis Rep CDR Wkly [serial online] 2006 [cited 25 May 2006]; 16(21): news. Available at http://www.hpa.org.uk/cdr/archives/2006/cdr2106.pdf.

2. HPA. Chikungunya outbreak in the Indian Ocean islands (and imported cases) - update. Commun Dis Rep CDR Wkly [serial online] 2006 [cited 24 May 2006]; 16(12): news. Available at: http://www.hpa.org.uk/cdr/archives/2006/cdr1206.pdf.

3. E Depoortere, D Coulombier, on behalf of the ECDC Chikungunya risk assessment group. Chikungunya risk assessment for Europe: recommendations for action. Eurosurveillance Weekly [serial online] 11 May 2006 [cited 24 May 2006]; 11(5). Available at http://www.eurosurveillance.org/ew/2006/060511.asp#2.

4. Institut de Vielle Sanitaire. Epidémie de Chikungunya à La Réunion / Océan Indien. Point de situation au 18 mai 2006 [online] [cited 24 May 2006]. Available at: http://www.invs.sante.fr/display/?doc=presse/2006/le_point_sur/ chikungunya_180506/index.html.

5. ProMED-mail. Chikungunya - Indian Ocean update (20): India, 1May 2006; 20060501.1261 [online]. Available at: http://www.promedmail.org/pls/promed/f?p=2400:1001:8292154 837732754153::NO::F2400_P1001_BACK_PAGE,F2400_P1001 _PUB_MAIL_ID:1010,32824.

6. Ocean Villas website. Chikungunya Update at 25 April 2006 [online] [cited 24 May 2006]. Available at http://www.ocean-villas.com/home/chikungunya.cfm.

7. International Federation of Red Cross and Red Crescent Societies. Seychelles: Chikungunya epidemic, Report No.MDRSC 001, [online] 10 March 2006 [cited 24 May 2006]. Available at http://www.ifrc.org/docs/appeals/06/MDRSC001.pdf.

8. HPA. Chikungunya virus in the Indian Ocean. Commun Dis Rep CDR Wkly [serial online] 2006 [cited 24 May 2006]; 16(6): news. Available at http://www.hpa.org.uk/cdr/archives/2006/cdr0606.pdf.

Links

Health Protection Agency information on chikungunya virus infection: http://www.hpa.org.uk/webw/HPAweb&Page&HPA
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