Klassevirus, a new member of the picornavirus family, has recently been discovered in human stool and more specifically linked with pediatric diarrhea.

Researchers from the U.S. and abroad detail their findings in the October 2010 issue of the journal Clinical and Vaccine Immunology.

Initial analysis of klassevirus shows it to be closely related to Aichi virus, a common cause of oyster-associated gastroenteritis in humans. Although studies have detected klassevirus in pediatric stool and sewage samples, it has not yet been found in any sterile sites of the human body leaving researchers to question its true authenticity as a human infection.

Prior studies of hepatitis A virus, a prototypic picornavirus, in chimps suggest that anti-3C antibodies only generate in actively infected individuals. Here, researchers developed a blood test for klassevirus infection incorporating recombinant klassevirus 3C protease (not present in picornavirus particles) to demonstrate human infection and determine prevalence in a sample pediatric group from hospitals in the St. Louis area. Results showed that anti-3C antibodies were detected up to 7 months following klassevirus infection indicating actual virus replication.

"The data in this study indicate that IgG antibodies are generated against the 3C protease after klassevirus infection," say the researchers. "This represents the first demonstration of a human antibody response to a klassevirus antigen and suggests that bona fide human infection by klassevirus occurs."