A new study in PLoS Medicine has shown that children who have rotavirus, a very common cause of diarrhea in children, and who have antigens (protein fragments from the surface of the virus) in their blood, also have infectious virus in their blood. Margaret Conner and colleagues from Baylor College of Medicine, Houston Texas, tested samples obtained from hospitalized children with gastroenteritis and compared them with samples taken from children admitted with bronchiolitis or noninfectious, nonchronic conditions and healthy adults.

Rotavirus antigen was detected in the blood of 51 of 57 of children with rotavirus-positive stools, in 8 of 9 of children without diarrhea but with rotavirus-positive stools, in 2 of 17 children with bronchiolitis of unknown cause without gastroenteritis, and in 5 of 41 children with gastroenteritis but with rotavirus-negative stools. No antigen was found in the blood of any other groups. A further study of 11 children who had antigen in their blood and 9 who did not showed that infectious virus was detected in the blood of all 11 children who were antigen-positive children but in just 2 out of 9 children who were antigen-negative.

The authors conclude that in the children studied most of those infected with rotavirus also had infectious virus in their blood. The presence of virus in the blood appears to be directly related to the presence of antigen in the blood but is independent of the presence of diarrhea. The finding of infectious rotavirus in the blood suggests that the disease is not limited to just the intestine. A related perspective by David Candy discusses the study’s findings further.