Characterization of a human pararotavirus.

A virus isolate with the properties of a pararotavirus was found after routine analysis by RNA electrophoresis of 658 samples of diarrheic feces from hospitalized infants and young children in Mexico City. Of the patients included in this survey, which was initiated in 1977, 29% excreted rotaviruses which were detected by their characteristic RNA pattern after gel electrophoresis. The morphology and sedimentation coefficient of this pararotavirus, which was the apparent cause of a diarrhea with moderate dehydration in a 2-year-old male infant, were indistinguishable from those of rotaviruses, but its buoyant density in CsCl was slightly higher than that of simian rotavirus SA11. By electron microscopy, the viral particles showed a regular pattern of cavities or holes that constituted the 5- and 6-coordinated units of the virion with a structure characteristic of T = 12. The virion also was apparently composed of protein classes similar to those found in rotaviruses. Seroconversion in the patient and presence of anti-pararotavirus antibodies in most of the members of the family of the patient was shown by immunoelectron microscopy. Of the sera from 12 healthy adults which were examined by this technique, seven were negative, three were slightly positive, and only two were strongly positive.