Clinical, molecular and serological outcomes of the Chikungunya outbreak in Grenada

OBJECTIVE: This study evaluated the clinical utility of Chikungunya (CHIKV) test results and clinical symptoms in patients with suspected CHIKV infection. DESIGN AND METHODS: Patients with CHIKV symptoms who presented at a health facility in Grenada during the recent outbreak had a CHIKV diagnostic test form completed by a health professional and a blood sample was drawn. The serum sample was stored at -80oC, shipped to the Naval Infectious Diseases Diagnostic Lab (NIDDL) on dry ice and tested for CHIKV and Dengue (DENV) using PCR real-time assay for viral RNA, and IgM detection by ELISA. RESULTS: Sera from more than 600 patients collected from mid September till mid October, 2014 were drawn and had a CHIKV diagnostic form completed. At the time of writing 112 patients sera have been tested at the NIDDL. 90% of patients had a positive test. PCR only was positive in 8% of patients. IgM only was positive in 83%, and both PCR and IgM were positive in 9% of patients. The major symptoms presented by patients were joint pain (84%), fever (81%), body pain (74%), headache (62%), chills (54%) and rash (49%). CONCLUSION: IgM testing detected 92% of test positive patients while PCR alone detected 17%. The IgM assay was clinically most useful. In an outbreak where dengue is ruled out and CHIKV is the cause, patients with the constellation of symptoms above could be considered positive for CHIKV infection with a 98% accuracy without confirmatory testing.