Rotavirus infection in children in Japan

Currently, a high morbidity of rotavirus diarrhea has been seen in children in developed and developing countries. Improvement of the vaccines is nece ssary in order to reduce the burden of diarrhea caused by rotavirus. A surv ey of rotavirus infection from diarrheal stool specimens in children of sev en regions in Japan was conducted from 1984 to 1999. The present study disc usses the survey results and reviews the national and international data of more than 23 papers and congress proceedings about rotavirus infection in Japan. We analyze the prevalence of rotavirus infection in acute diarrheal in- and outpatients, the distribution of rotavirus G-serotypes and surveill ance data for seasonality and age groups in Japan. The data indicated that rotavirus is the most important cause of diarrhea in Japan among young chil dren, with the prevalence ranging from approximately 9.7 to 88%. The most c ommon rotavirus strains belonged to serotype G1, specifically since 1993. S erotypes G2, G3 and G4 had also been documented to be predominantly based i n the area and year before 1992. However, untypeable rotavirus strains had been found each year, with a prevalence up to 56.7% which suggests that rar e serotypes (except G1-4) or new serotypes might exist. Unexpectedly, in To kyo and Sapporo from 1998 to 1999, G9 was found to be the first most prevai ling serotype with a high prevalence of 52.9 and 71.4%, respectively. Despi te these data from different geographic areas, the year under investigation was relatively clear in respect to seasonality, with a peak of rotavirus a ctivity in late winter (February) through early spring (March). Age distrib ution had also characterized that the infection was predominant among child ren aged 1-2 years of age, although it was also common in children of 2-3 y ears. In addition, mixed infection with bacteria was documented.