Concurrent outbreaks of Chikungunya and Dengue fever in Kandy, Sri Lanka, 2006–07: a comparative analysis of clinical and laboratory features

OBJECTIVES: To compare the clinical and laboratory features of confirmed cases of Chikungunya and Dengue fever; to validate the clinical diagnosis based on serology. METHODS: Cases with a clinical diagnosis of Chikungunya and Dengue fever were recruited for seroconfirmation during a concurrent epidemic in 2006-07, at the General Hospital, Peradeniya, Sri Lanka. RESULTS: Of 54 patients with fever, serology confirmed 21 with Chikungunya infection, 20 with Dengue infection, and three co-infections, with sensitivity of the clinical diagnosis of 92% for Chikungunya fever and 95% for Dengue fever. The mean age of patients with Chikungunya fever was 45 years (range 21-74 years), and patients with Dengue fever was 30 years (range 15-63 years) (p = 0.005). Sixteen (70%) of Chikungunya fever patients were females, while 15 (71%) of those with Dengue fever were males (p = 0.007). Arthralgia was common to both groups (p = 0.155), while headache and a bleeding tendency were observed more in patients with Dengue fever. Twelve (57%) Chikungunya cases had acute arthritis compared with none in the Dengue group (p = 0.001), lasting mean 6 days (range 1-14 days). They developed chronic arthritic disability (range 1-6 months). Leucopenia was common to both Chikungunya and Dengue fever patients. However, thrombocytopenia was more pronounced in the Dengue patients (mean (SD) platelet count 75 (34)x10(9)/l) than in the Chikungunya patients (117 (70)x10(9)/l) (p = 0.001). In the Chikungunya group there was a positive correlation between duration of the illness and the platelet count (r = 0.181, p = 0.194), but the Dengue group showed a negative correlation (r = -0.309, p<0.001). CONCLUSION: Most of the clinical and laboratory features of patients with Chikungunya and Dengue fever are similar. Arthritis is the pathognomonic sign in patients with Chikungunya fever.