EVALUATION OF LABORATORY DIAGNOSIS OF THE FIRST NOROVIRUS OUTBREAK IN TURKEY IN 2008

Abstract

Norovirus (NoV) is one of the most prominent agents of gastroenteritis and water/food-borne outbreaks affecting all of the age groups in the world. As the identification of the etiologic agent is important during gastroenteritis outbreaks, it is recommended to combine two different methods for rapid and reliable laboratory diagnosis of NoV. Although Nov outbreaks have been observed in many different countries of the world, there was no report on "NoV outbreak" in Turkey till 2008 due to the absence of a regular surveillance system for non-bacterial gastroenteritis. This study aimed to present the laboratory results for "the first Nov outbreak" in Turkey in 2008. A number of cases with diarrhea and nausea/vomiting initially emerged in Aksaray (located at the southern part of central Anatolia) in May 2008, followed by cases from Sereflikochisar, Kirsehir, and Adana provinces (located at central and southern Anatolia; geographically closer regions). However, regional laboratories declared that no known bacterial (Salmonella spp., Shigella spp., enterotoxigenic Escherichia coli), viral (Rotavirus, Adenovirus) and parasitic agents were detected. A total of 50 stool samples were sent to the Virology Reference Laboratory (Refik Saydam Hygiene Center, Ankara) for further investigations including NoV. For the investigation of NoV, the samples were analysed by using antigen-ELISA (Ridascreen, R-Biopharm, Germany) and real-time polymerase chain reaction(PCR) (Roche Diagnostics GmbH, Germany) methods. Of the samples, 26% (13/50) were found antigen positive, whereas 33% (13/40) were positive for viral nucleic acids. The positivity rates determined by ELISA and PCR were as follows, respectively; 57% (4/7) and 71% (517) in Aksaray, 25% (1/4) and 25% (1/4) in Sereflikochisar, 28% (7125) and 40% (6/15) in Kirsehir, 7% (1/14) and 7% (1/14) in Adana. Nine (69.2%), and 4 (30.8%) out of 13 positive samples were genotyped as NoV GI and GII, respectively. The sensitivity and specificity of antigen-ELISA method were found as 61.5% and 100%, respectively, when compared with real-time PCR. In conclusion, further epidemiological studies and genomic analysis are needed for the detection and control of circulating strains in Turkey, since Nov outbreaks spread rapidly and cause serious economical and workforce loss.