Continued Circulation of G12P[6] Rotaviruses Over 28 Months in Nepal: Successive Replacement of Predominant Strains

<i>Rotavirus A</i> causes severe diarrhoea in infants and young children worldwide. The migration pattern (electropherotype) of the double-stranded RNA genome upon polyacrylamide gel electrophoresis has been used to define “strains” in molecular epidemiology. In temperate countries, distinct electropherotypes (strains) appear after the annual, off-seasonal interruption of rotavirus circulation. In Nepal, rotavirus circulated year-round and an uncommon genotype G12P[6] predominated and persisted, providing a unique opportunity to examine whether the same electropherotype (the same strain) persisted or new electropherotypes (new strains) emerged successively under the same G12P[6] predominance. A total of 147 G12P[6] rotaviruses, collected from diarrhoeal children in Nepal between 2007 and 2010, were classified into 15 distinct electropherotypes (strains). Of these, three electropherotypes (strains), LP1, LP24, and LP27, accounted for 10%, 32% and 38% of the G12P[6] rotaviruses, respectively. Each of the three major strains successively appeared, dominated, and disappeared. This study provided new evidence for the hypothesis that rotavirus constantly changes its strains to predominate in the local population even under conditions where a single genotype predominates and persists. Such dynamic strain replacement, the constant takeover of one predominant strain by another, fitter strain, is probably gives a competitive edge to the survival of rotavirus in nature.

Prevalence and Identification of Rotaviruses in Stool Specimens of Patients with Acute Diarrhea from Several Regions of Korea

PURPOSES: Rotaviruses are the main cause of infantile diarrheal diseases worldwide. The purpose of this study is to obtain epidemiologic data of rotavirus infections in Korea. METHODS: Stool specimens were collected from 150 patients with acute diarrheal symptoms, who were admitted to Yonsei Medical Center and Chungbuk National University Hospital. After isolating the virus from the specimens, the viruses were identified as rotaviruses by electron microscope and fluorescent microscope after staining with rotavirus VP6-specific monoclonal antibody. RNA was extracted from the specimens by modified phenol/chloroform method. Electropherotying was done with extracted RNA samples after silver staining of the gels. Rotavirus serotyping was done using commercial serotyping ELISA kit. RESULTS: Rate of infection from rotavirus stool samples was 60%. Isolated rotaviruses were all serogroup A and a majority(46.0%) of these viruses were long type. Serotypes 1 and 2 were identified with serotype 1 being the majority(52.2%). There were no differences in these types between 1991 and 1992, and also between Seoul and Cheongju area. CONCLUSION: Electropherotype of rotavirus epidemic in Korea was serogroup A, and long type in the majority. Serotypes of rotavirus epidemic in Korea were type 1 and type 2. These results show that the rotavirus reassortant vaccine developed in America could also handle the rotaviral disease in Korea.