The genomic RNA of human astrovirus was sequenced and found to contain 6797 nt organized into three open reading frames (la, lb, and 2). A potential ribosomal frameshift site identified in the overlap region of open reading frames la and lb consists of a "shifty" heptanucleotide and an RNA stem-loop structure that closely resemble those at the gag-pro junction of some retroviruses. This translation frameshift may result in the suppression of in-frame amber termination at the end of open reading frame la and the synthesis of a nonstructural, fusion polyprotein that contains the putative protease and RNA-dependent RNA polymerase. Comparative sequence analysis indicated that the protease and polymerase of astrovirus are only distantly related to the respective enzymes of other positive-strand RNA viruses. The astrovirus polyprotein lacks the RNA helicase domain typical of other positivestrand RNA viruses of similar genome size. The genomic organization and expression strategy of astrovirus, with the protease and the polymerase brought together by predicted frameshift, most dosely resembled those of plant luteoviruses.

Analysis of foodborne outbreaks shows how advances in viral diagnostics are clarifying the causes of foodborne outbreaks and determining the high impact of norovirus infections.

Novel enteric viruses such as astrovirus and picobirnavirus may be more important etiologic agents of diarrhea in HIV-infected patients than previously recognized and may be more common than either bacterial or parasitic enteropathogens.

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We documented transmission by food and person-to-person contact; persistence of virus despite sanitization onboard, including introductions of new strains; and seeding of an outbreak on land.

Surveillance of Ebola virus disease flare-ups uncovers a reduced rate of Ebola virus evolution during persistent infections.

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In June 1991, a large outbreak of acute nonbacterial gastroenteritis occurred among students and teachers at 10 primary and 4 junior high schools in Katano City, Osaka, Japan. The outbreak affected > 4700 persons, lasted 5 days, and was believed to have been linked to contaminated food from a common supplier. Astrovirus, identified as the etiologic agent, was detected by direct electron microscopy in 10 of 38 fecal samples obtained from patients with diarrhea. Detection was confirmed by solid-phase immune electron microscopy (IEM), EIA, reverse transcription-polymerase chain reaction, and virus isolation in CaCo-2 cells. Several patients who had astrovirus in their stool also demonstrated a significant antibody response to a reference strain of astrovirus by IEM and EIA and to their own isolate by IEM. Astrovirus can be an important agent of epidemic acute nonbacterial gastroenteritis in school-aged children and adults in Japan.