An outbreak of food-borne gastroenteritis due to sapovirus among junior high school students.

The human sapovirus (SaV) causes acute gastroenteritis mainly in infants and young children. A food-borne outbreak of gastroenteritis associated with SaV occurred among junior high school students in Yokohama, Japan, during and after a study trip. The nucleotide sequences of the partial capsid gene derived from the students exhibited 98% homology to a SaV genogroup IV strain, Hu/Angelholm/SW278/2004/SE, which was isolated from an adult with gastroenteritis in Solna, Sweden. An identical nucleotide sequence was detected from a food handler at the hotel restaurant, suggesting that the causative agent of the outbreak was transmitted from the food handler. This is the first description of a food-borne outbreak associated with the SaV genogroup IV strain in Japan.

Norovirus-associated encephalopathy.

Norovirus is a common cause of gastroenteritis. We describe the case of a 23-month-old girl with encephalopathy possibly associated with norovirus infection. The viral genome was detected in stool, serum and cerebrospinal fluid (CSF) by reverse transcription polymerase chain reaction. This is the first report of encephalopathy potentially caused by norovirus as indicated by the presence of the virus genome in CSF.

Analysis of a long-term discrepancy in drug-targeted genes in plasma HIV-1 RNA and PBMC HIV-1 DNA in the same patient.

Drug-resistance genotypes were investigated in a patient under treatment with anti-HIV drugs. Since the drug resistance-associated mutations in plasma HIV-1 RNA and proviral DNA in peripheral blood mononuclear cells (PBMCs) were inconsistent, changes were followed over time, and the discrepancy was shown to persist for a long period. In plasma HIV-1 RNA, D67N, K70R, T215Y, and Y188L were present in the reverse transcriptase (RT) region, and two primary mutations, I84V and L90M, were noted in the protease (Pro) region. In contrast, in proviral DNA, no drug resistance-associated mutations were found in the RT region, and mutations such as L90L/M were only infrequently present in the Pro region. This situation persisted for more than 3 years. In addition, sequencing analysis of the V3 loop in the envelope gene showed that non-syncytium-inducing/macrophage-tropic viruses contribute to acquisition of drug resistance. In this study, drug-resistant viruses were produced primarily at macrophages, and drug-sensitive viruses were maintained in PBMCs as a reservoir.

[An epidemiological study of respiratory syncytial virus infection in Yokohama, Japan for five years].

The epidemiologic features of respiratory syncytial virus (RSV) infection were investigated by detecting the virus in throat swab specimens from patients with acute respiratory symptoms attending the sentinel surveillance clinics in Yokohama City in 5 seasons from July 1998 to June 2003. Throughout the 5 seasons, RSV was found from 181 in 2683 specimens tested (6.7%) by virus isolation in cell culture or genome detection using nested RT-PCR, and this detection rate followed that of influenza virus (infl.v.) (441/2683; 16.4%), while the proportion of RSV isolates in a season fluctuated from 12 to 22% of all causative viruses identified. Analysis of monthly detected number of strains revealed that the peak of RSV isolation was present in December which preceded that of infl.v. by 2 months. Moreover, RSV strains were isolated sporadically during late spring to early autumn (from May to September) when infl.v. was scarcely detected. Among 181 RSV strains, 172 could be subgrouped; 104 were identified as subgroup A, while 68 were B. Subgroup A were detected more frequently throughout the 5 seasons (57%), though the proportion varied seasonally and subgroup B exceeded both in 2000/2001 and 2002/2003 seasons (61% and 70%, respectively). Clinical characteristics of RSV-infected patients were compared with those infected with infl.v. Age distribution of cases revealed that RSV detected predominantly (79%) from lower age groups (less than 5 years) compared to infl. v (41%). As for the proportion of cases showing clinical symptoms of lower respiratory inflammation predominated in RSV-infected irrespective of age groups.

Isolation of influenza A H1N2 viruses from an outbreak in Yokohama City during the 2001-2002 influenza season in Japan.

Emergence of Influenza A H1N2 viruses was documented worldwide during the 2001-2002 influenza season. In Japan, H1N2 viruses were isolated from two students of a junior high school in an influenza outbreak in Yokohama City, February 2001. Genetic and antigenic analyses demonstrated that the H1N2 viruses isolated in Japan shared common features with those isolated in other countries.