Shigekazu Nakaya

Molecular epidemiology of astroviruses in Japan from 1995 to 1998 by reverse transcription-polymerase chain reaction with serotype-specific primers (1 to 8).

In addition to the serotype‐specific primers described previously (1 to 7), a new serotype 8‐specific primer has been designed, allowing detection of all astrovirus serotypes. A total of 1,382 diarrheal stool samples in 5 regions in Japan were examined by reverse transcription‐polymerase chain reaction (RT‐PCR). The incidence of astrovirus infection in all 5 regions was 5.9% (82 of 1,382 samples) and infection occurred mainly from November to April. Serotypes 1, 3, and 4 were detected in 66, 14, and 2 of the 82 positive samples, respectively. None of the other serotypes was detected. The highest detection rate was from 0 to 1 year old, 39.0%, and the next highest was from 1 to 2 years old, 34.1%. The primers provide a useful approach for study of the epidemiology of astroviruses. J. Med. Virol. 61:326–331, 2000.

Rotavirus infection in children in Japan

Abstract Currently, a high morbidity of rotavirus diarrhea has been seen in children in developed and developing countries. Improvement of the vaccines is necessary in order to reduce the burden of diarrhea caused by rotavirus. A survey of rotavirus infection from diarrheal stool specimens in children of seven regions in Japan was conducted from 1984 to 1999. The present study discusses 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 surveillance data for seasonality and age groups in Japan. The data indicated that rotavirus is the most important cause of diarrhea in Japan among young children, with the prevalence ranging from approximately 9.7 to 88%. The most common rotavirus strains belonged to serotype G1, specifically since 1993. Serotypes G2, G3 and G4 had also been documented to be predominantly based in 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 rare serotypes (except G1–4) or new serotypes might exist. Unexpectedly, in Tokyo and Sapporo from 1998 to 1999, G9 was found to be the first most prevailing serotype with a high prevalence of 52.9 and 71.4%, respectively. Despite these data from different geographic areas, the year under investigation was relatively clear in respect to seasonality, with a peak of rotavirus activity in late winter (February) through early spring (March). Age distribution had also characterized that the infection was predominant among children aged 1–2 years of age, although it was also common in children of 2–3 years. In addition, mixed infection with bacteria was documented.

Detection of Astroviruses from Stool Samples in Japan Using Reverse Transcription and Polymerase Chain Reaction Amplification

We developed a reverse transcription and polymerase chain reaction (RT‐PCR) method for detecting astrovirus serotypes 1, 2, 3, 5, 6 and 7 (but not serotype 4). Furthermore, we developed the specific primers for detecting serotypes 1 and 2, the most predominant serotypes in the world. Sensitivity of the first PCR with serotype common primers was about 10 times higher than that of enzyme immunoassay with monoclonal antibody (EIA‐MAb). Sensitivity of the second PCR with the serotype‐specific primers was even higher. The RT‐PCR method was useful for detecting astroviruses from clinical samples, especially serotypes 1 and 2.

Diagnosis and Clinical Manifestations of Diarrheal Virus Infections in Maizuru Area from 1991 to 1994

Rotavirus (44.7%), adenovirus (5.6%), small round structured viruses such as astrovirus (9.8%) and Norwalk like virus (6.9%) were detected by latex agglutination and reverse transcription polymerase chain reaction amplification from 378 stool samples in an outpatient clinic of Pediatrics in Maizuru area from 1991 to 1994. 70.0% were found from 6 months to 2 years old and 91.0% were detected from January to April. Serotype 1 astrovirus and group 2 Norwalk like virus were mainly found in all serotypes in each virus. Diarrhea, vomiting, nausea, fever, cough and rhinorrhea, and severity of diseases were examined in each case. Fever is significantly found in patients with rotavirus. Sporadic cases with small round structured viruses were recognized in the outpatient clinic of pediatrics.