Differential Diagnosis of Chikungunya, Dengue Viral Infection and Other Acute Febrile Illnesses in Children

Background: Clinical manifestations of chikungunya (CHIK) are similar to those of dengue. It would be useful to be able to identify clinical manifestations that could reliably help to differentiate CHIK from dengue and other acute febrile illnesses during a CHIK outbreak in a dengue-endemic area. Methods: A prospective cohort study was conducted between April and July 2009 in children aged 1 month to 15 years who lived in a CHIK outbreak area in southern Thailand and who had fever <7 days with arthralgia/arthritis, myalgia or rash. CHIK was confirmed by real-time polymerase chain reaction or the indirect immunofluorescence test. Results: Fifty patients were suspected of having CHIK, of whom 32 were confirmed, 1 had coinfection with dengue viral infection (DVI), 10 had dengue alone and 7 had an acute febrile illness. The specificity and positive predictive value of fever and arthralgia together to diagnose CHIK were 47.1% and 74.2%, and the corresponding values of the standard clinical triad (fever, arthralgia, rash) were 70.6% and 83.3%, respectively. Fever ⩽2 days, skin rash during fever and white blood cell count ≥ 5000 cells/mm3 were independently and significantly associated with CHIK in comparison with DVI and acute febrile illnesses, with relative risk ratios (95% confidence intervals) of 10.4 (0.9–116) and 13.7 (1.3–145), 13.8 (1.2–164) and 14.8 (1.6–168), and 18.3 (1.7–194) and 1.8 (0.1–20.6), respectively. Conclusions: During a CHIK outbreak in a DVI-endemic area, overdiagnosis of CHIK was common. Skin rash during fever and white blood cell count ≥ 5000 cells/mm3 or specific antigen testing (if available) can be helpful in differentiating CHIK from DVI.