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.

Establishment of laboratory testing capability for chikungunya virus in Grenada, West Indies

OBJECTIVE: Rapid diagnosis of Chikungunya (CHIKV) is important early in an epidemic. The study objective was to describe the process of implementing CHIKV testing capability in Grenada and to confirm the arrival of CHIKV on the main island of Grenada. DESIGN AND METHODS: In April, 2014 a collaborative study between the U.S. Naval Infectious Diseases Diagnostic Laboratory (NIDDL) and the clinical microbiology laboratory of St. George’s University (SGU) was started. SGU acquired essential instrumentation and patient samples, and NIDDL provided supplies and reagents, plus technical training experts. RESULTS: Personnel, supplies and equipment arrived in Grenada in August 2014. Set up of instruments and test validation were completed quickly. Initial CHIKV PCR and IgM tests found 3 PCR positive samples. The IgM assay found several presumptive positives that were unable to be confirmed due to ELISA instrument malfunction. PCR data indicated that CHIKV had arrived on the main island of Grenada no later than August, 2014. Based on arbovirus test demand, symptomatic patients began to increase in August, peaked in September, and tailed off during November. CONCLUSION: Both CHIKV tests were implemented and produced the first on-island reference test confirmation of CHIKV patients in Grenada. The most difficult part of this effort was training technologists in time to help with testing. Laboratory testing for CHIKV infection can be a challenge in developing states at a distance from support services. Collaborative links with established labs remains essential.