Clinical Updates
18 January 2008
Dengue fever and chikungunya virus activity
This update reports on some of the current dengue and chikungunya virus (CHIKV) outbreaks; it is not a comprehensive listing of all outbreaks.
Africa
Over 17,000 cases of CHIKV infection have been reported from Gabon between January and June 2007 [1].
Asia
In 2007, Cambodia experienced its largest outbreak of dengue. By 29 August 2007, a total of 34,542 cases including 365 deaths were reported [2]. After August, case numbers declined. Media reports have suggested nearly 40,000 cases were reported for the whole of 2007, including 407 deaths [3].
India has reported outbreaks of both dengue and CHIKV during 2007. Between 1 January and 5 November, India reported 3,683 cases of dengue including 49 fatalities and 37,838 suspected cases of CHIKV infection, 1411 of which were confirmed. Cases of dengue have been reported in 17 states of India, and cases of CHIKV infection in 13. In both outbreaks, Kerala was the most affected state (24,031 suspected cases of CHIKV infection and 603 cases of dengue reported between 1 January 2007 and 5 November 2007) [4].
A total of 15,207 cases of CHIKV infection have been reported from Indonesia between January 2001 and June 2007 [1]. Media reports suggest there has also been a large outbreak of dengue in Indonesia, with outbreaks of both dengue and CHIKV reported in the States of East Java, Central Java and Greater Jakarta [5-8].
During 2007, imported cases of both dengue and CHIKV from Indonesia were reported in Taiwan [9, 10]. Between June and December 2007, indigenous cases of dengue were reported in Taiwan and by 12 October 2007, media reports suggested that it was the largest ever dengue outbreak [11]. In November 2007, the Centre for Disease Control, Taiwan reported 587 cases of dengue [12].
In Viet Nam, the number of cases of dengue reported from Hanoi between January and July 2007 was 70% higher than the number reported during the same period of 2006 [13]. Media reports suggest that nearly 88,000 cases were reported nationwide between 1 January and 26 October 2007 [14].
Caribbean
Between January and July 2007, 1,900 cases of dengue were reported in Dominican Republic [15]. As of 7 December 2007 this figure stood at 9,349 [16].
In Guadeloupe, as of 27 July 2007, 3,874 cases of dengue were reported compared to 2,948 in the whole of 2006 [17].
In Puerto Rico, as of 7 December 2007, 10,607 cases of dengue were reported, compared to 3,043 in 2006 [16].
Other Caribbean countries reporting cases of dengue include Barbados and Jamaica [18].
Six imported cases of dengue have been reported in the Cayman Islands introduced from residents returning from elsewhere in the Caribbean [19].
Central America
In Central America the countries most affected by dengue include Costa Rica (26,109 cases as of 14 December 2007), El Salvador (12,360 cases as of 14 December 2007); Honduras (33,268 cases as of 14 December 2007) and Mexico (30,748 cases as of 19 October 2007 [16].
South America
A dengue epidemic has been reported in Brazil; 481,300 cases were recorded between January and September 2007 [16, 17]. The largest increase has been in Rio de Janeiro State where since January 2007, 55,467 cases have been reported [18]. This is more than the total number of cases reported in the state during the four previous years. Large outbreaks were also reported in Colombia (41,773 cases as of 14 December 2007), Paraguay (28,182 cases as of 26 November 2007) and Venezuela (80,646 cases in 2007) [16].
Further information on dengue and chikungunya outbreaks in specific countries can be found in the NaTHNaC Outbreak Surveillance Database.
Dengue fever
Dengue is transmitted via the bite of an infected Aedes mosquito; A. aegypti is the principle vector, but A. albopictus is also of importance. Dengue is recognised in more than 100 countries. Between 250,000 to 500,000 cases are reported to the World Health Organization annually, although there is substantial underreporting. The major disease burden occurs in the Americas, South East Asia and the western Pacific.
The majority of cases of dengue are sub-clinical or mild. However, dengue can progress to the more serious dengue haemorrhagic fever. This form of dengue is more common in children and is rarely seen in travellers.
CHIKV
CHIKV is transmitted via the bite of an infected Aedes mosquito. It is endemic to large parts of Africa, the Middle East, India, and South East Asia.
Initial symptoms of CHIKV infection include a sudden onset of severe arthralgias and myalgias, accompanied by fever, headache and conjunctivitis, and rash. The acute illness usually resolves over three to five days. Most patients recover fully over a period of a few weeks.
Advice for travellers
There is no vaccine available to protect against dengue or CHIKV infection. Travellers to endemic areas can reduce their risk of both diseases by practising mosquito bite avoidance measures. Aedes mosquitoes are most active during daylight hours. Particular vigilance with bite avoidance should be taken around dawn and dusk.
References
1. World Health Organization. Chikungunya outbreak reported countries, as of October 2007. [Accessed 18 January 2007]. Available at http://www.reliefweb.int/rw/fullMaps_Af.nsf/luFullMap/D72A4CA
406BD7A9F852573B5007CABE3/$File/who_HLT_wrl071218.
2. International Federation of Red Cross and Red Crescent Societies. Cambodia: DREF Bulletin, Cambodia: Dengue fever. [Online resource] 29 August 2007 [accessed 18 January 2008]. Available at http://www.ifrc.org/docs/appeals/07/mdrkh00101.pdf
3. ProMED-mail. Dengue/DHF update 2008 (02): 2008 ProMED-mail 2008; 13 Jan: 20080113.0170. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:546748
5654184654282::NO::F2400_P1001_BACK_PAGE,F2400_P1
4. Institut de Veille Sanitaire. Bulletin Hebdominaire International No 115. 29 November – 5 December 2007. [Accessed 18 January 2008] Available at http://www.invs.sante.fr/international/bhi/bhi_051207.pdf
5. ProMED-mail. Dengue/DHF update 2007 (50): 2007 ProMED-mail 2007; 27 Dec: 20071227.4147. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:107636
66968574375867::NO::F2400_P1001_BACK_PAGE,F2400_P1
6. ProMED-mail. Dengue/DHF update 2007 (48): 2007 ProMED-mail 2007; 11 Dec: 20071211.3989. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:15495
013189528520714::NO::F2400_P1001_BACK_PAGE,F2400_
7. ProMED-mail. Chikungunya (04): Indonesia (Java), Request for information: 2007 ProMED-mail 2007; 17 Dec: 20071217.4062. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:87585
29407522895888::NO::F2400_P1001_BACK_PAGE,F2400_P
8. ProMED-mail. Chikungunya (02): Indonesia (Java), suspected: 2007 ProMED-mail 2007; 1 Dec: 20071201.3876. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:88273
96762663191376::NO::F2400_P1001_BACK_PAGE,F2400_P
9. ProMED-mail. Chikungunya: Taiwan ex Indonesia: 2007 ProMED-mail 2007; 9 Jan: 20080109.0106. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:50392
68926979018351::NO::F2400_P1001_BACK_PAGE,F2400_P
10. ProMED-mail. Dengue / DHF update: Taiwan ex Viet Nam, Indonesia, Thailand: 2007 ProMED-mail 2007; 20 Jun: 20070620.1996. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:39707
3894765137400::NO::F2400_P1001_BACK_PAGE,F2400_P1
11. ProMED-mail. Dengue/DHF update 2007 (39): 2007 ProMED-mail 2007; 17 Oct: 20071017.3396. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:54674
85654184654282::NO::F2400_P1001_BACK_PAGE,F2400_P
12. Centre for Disease Control, Taiwan. CDC releases latest surveillance data on notifiable infectious diseases in Taiwan (November, 2007); Dengue fever remains the leading disease for imported cases, 20 Dec 2007 [Accessed 18 January 2008]. Available at: http://nhcc.cdc.gov.tw/en/e_index_news_20051027.asp?data
13. Australian Government Department of Health and Ageing. International surveillance reports. 7 to 17 August 2007. [Accessed 18 January 2008]. Available at http://www.health.gov.au/internet/wcms/publishing.nsf/Content
14. ProMED-mail. Dengue/DHF update 2007 (42): 2007 ProMED-mail 2007; 30 Oct: 20071030.3516. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/askus/f?p=2400:1001:7056527
535531835636::NO::F2400_P1001_BACK_PAGE,F2400_P100
15. ProMED-mail. Dengue/DHF update 2007 (21). ProMED-mail 2007; 21 May: 20070521.1616. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:588040
4399910283687::NO::F2400_P1001_BACK_PAGE,F2400_P10
16. Pan American Health Organization. Number of reported cases of dengue & dengue hemorrhagic fever, regions of the Americas, 2007, 10 January 2008. [Accessed 18 January 2008]. Available at http://www.paho.org/English/AD/DPC/CD/dengue-cases-2007.htm
17. Pan American Health Organization. Number of reported cases of dengue & dengue hemorrhagic fever, regions of the Americas, 2006, 17 April 2007. [Accessed 17 January 2008]. Available at http://www.paho.org/english/ad/dpc/cd/dengue-cases-2006.htm
18. ProMED-mail. Dengue/DHF update 2007 (41). ProMED-mail 2007; 24 Oct: 20071024.3457. [Accessed 18 January 2008]. Available at http://www.promedmail.org/pls/promed/f?p=2400:1001:11255
281976249979846::NO::F2400_P1001_BACK_PAGE,F2400_P
19. Wheeler A, Petrie W. An overview of Aedes aegypti and Aedes albopictus control in the British Overseas Territory of the Cayman Islands. Euro Surveill 2007;12(11): E071122.3. Available at http://www.eurosurveillance.org/ew/2007/071122.asp#3
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