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Chikungunya Fever Outbreak, Bhutan, 2012

Year: 2013

Type: article

Abstract: In 2012, chikungunya virus (CHIKV) was reported for the first time in Bhutan.IgM ELISA results were positive for 36/210 patient samples; PCR was positive for 32/81.Phylogenetic analyses confirmed that Bhutan CHIKV belongs to the East/Central/South African genotype.Appropriate responses to future outbreaks require a system of surveillance and improved laboratory capacity.C hikungunya fever is caused by infection with chi- kungunya virus (CHIKV; family Togaviridae, genus Alphavirus).CHIKV was first isolated from humans and mosquitoes during an epidemic of chikungunya fever in Newala, Tanzania, during 1952Tanzania, during -1953 (1) (1).The virus is transmitted to humans primarily by Aedes aegypti and Ae.albopictus mosquitoes.Chikungunya fever can cause lingering joint pain, often lasting several weeks; the disease is rarely life-threatening and, unlike dengue virus infection, does not cause severe hemorrhagic manifestations or shock (2).Outbreaks of chikungunya fever are sporadic, and there is no licensed vaccine to protect against the disease.In addition to the chikungunya fever epidemic in Tanzania in 1952Tanzania in -1953, several other outbreaks have affected millions of persons in eastern, western, and central Africa and Asia.The first of many chikungunya fever outbreaks in Southeast Asia was reported in Bangkok, Thailand, in 1958, followed by outbreaks in Sri Lanka; Kolkata and Chennai, India; and elsewhere (3-6).CHIKV reemergence in Indonesia and India caused epidemics during 1999-2003 and 2005-2006, respectively; 1.3 million cases of chikungunya fever occurred in India during the epidemics (6,7).In 2004, a chikungunya fever outbreak occurred in the Indian Ocean region.On Réunion Island, 266,000 cases, affecting ≈40% of the population, and ≈250 deaths were recorded (7).We report details of a chikungunya fever outbreak in Bhutan in July 2012; CHIKV had not been reported in Bhutan before this outbreak. The StudyIn July 2012, the Public Health Laboratory (PHL), Department of Public Health, Ministry of Health, in Thimphu, Bhutan, received reports of suspected chikungunya fever cases.A total of 215 acute-phase serum samples were obtained from patients at hospitals in the southwestern districts of Samtse, Chukha, and Thimphu (online Technical Appendix Figure, wwwnc.cdc.gov/EID/article/19/10/13-0453-Techapp1.pdf) and sent to PHL for testing (Table 1) (8).Samples were maintained at 4°C until arrival at PHL.Most patients from whom a serum sample was obtained were inpatients 15-44 years of age.Of the 215 samples, 84 (39%) were from female patients (mean age of 27.2 years, range 4 months to 68 years, and 131 (61%) were from male patients (mean age 31.5 years, range 2-78 years).Serum samples from 210 of the 215 patients were tested for CHIKV IgM by ELISA (Table 1).The CHIKV ELISA was developed by the National Institute of Virology in Pune, India, and supplied to PHL by the World Health Organization.Of the 210 samples, 36 (17.1%) were positive for CHIKV IgM.As determined by Fisher exact test, there were no significant differences in the percentage of IgM ELISA-positive cases in the 3 districts (p>0.2) or for male versus female patients (p>0.08).Medical records were provided for only 79 patients; significantly fewer records were provided for patients in Chuka than for patients in Samtse and Thimphu (p>0.003).Of the 79 patients with medical records, all had a fever, 48 (60.1%) had arthralgia, 55 (69.6%) had headache, and 6 (7.6%) had a rash (8).There were no substantial differences in the distribution of symptoms by patient sex of district of residence.The first 78 (37%) acute-phase serum samples received by PHL were shipped frozen to the Armed Forces Research Institute of Medical Sciences (AFRIMS) in Bangkok, Thailand, for testing by nested reverse transcription PCR (RT-PCR) amplification of the capsid gene (Table 2) (9).Of these 78 samples, 32 (41%) were positive for CHIKV.The difference in distribution of positive and negative RT-PCR results by patient sex was not statistically significant in any of the 3 districts (p>0.1,Fisher exact test).Of 8 IgM ELISA-positive samples sent to AFRIMS for testing, 4 (50%) were positive by RT-PCR, and of 67 IgM ELISAnegative samples sent to AFRIMS for testing, 27 (40.3%)were positive (Table 2).The first RT-PCR-confirmed CHIKV-positive specimen was collected on July 12, 2012, from a patient for whom the date of illness onset was listed as July 11.On July 9, the patient had traveled through West Bengal, India, en route from Thimphu to Samtse, Bhutan.All confirmed chikungunya fever case-patients in Thimphu had traveled to Phuentsholing, Bhutan, or other places in southern Bhutan affected by the outbreak.

Source: Emerging infectious diseases

DOI: 10.3201/eid1910.130453