April 19, 2007
HOUSTON - Most of the children who have diarrhea caused by rotavirus infection also have evidence of the virus in their blood – a factor that warrants further study to determine if it contributes to other kinds of disease, said Baylor College of Medicine researchers who published a report of their work online today in the Public Library of Science Medicine, an open-access professional journal.
"Before this work, we thought the infection was limited to specific cells in the gastrointestinal tract," said Dr. Margaret Conner, associate professor of molecular virology and microbiology at BCM and research scientist at Michael E. DeBakey VA Medical Center in Houston.
This means that rotavirus may be responsible for other non-diarrheal symptoms in children with or without diarrhea. While it is possible that the finding could have significance for other diseases, Conner said it would require a study of children who seek treatment for a variety of infections to determine if and what kinds of problems are associated with rotavirus infection in the blood.
Some physicians who treat children with rotavirus infections suspected that some symptoms – fever, occasional convulsions – pointed to a more body-wide infection, but the virus had not been found in the blood or elsewhere consistently, she said. It is important that all doctors now recognize that rotavirus is a systemic infection.
This work was begun when Dr. Sarah Blutt, the study's first author and now an assistant professor in the same department, found antibodies to the virus in lymph nodes of mice early during infection. Blutt and Conner decided to look for the virus in the blood and they found it in mice and other animals. Then they looked for and found the virus in old human samples contributed by researchers in Australia who were the first to identify human rotavirus.
In the current study, Conner, Blutt and their colleagues looked in blood samples from children who were thought to have rotavirus and in those who were not known to have the infection. They found evidence of rotavirus protein or antigen in the blood of 51 of 57 children with stools positive for rotavirus, in eight of nine children who did not have diarrhea but did have rotavirus-positive stools, in 2 of 17 children who did not have gastrointestinal problems but did have bronchiolitis (a lung infection) of unknown cause and in five of 41 children with gastrointestinal infection but not evidence of rotavirus in the stool. They found rotavirus in no other groups.
"We could find antigenemia (the presence of antigen) in the blood of 90 percent of children with rotavirus infection," said Conner. "It is indicative that most of the children have a systemic infection."
"One of the key points of our work was we showed that there was infectious virus in the blood, which suggests that there is infectious virus throughout the body," she said. "There is the potential then for rotavirus to cause diseases other than diarrhea."
"Virtually everyone is infected with rotavirus by the age of two," she said. In developing countries, it happens even younger. Also, people of all ages can be infected, not just children.
Others who took part in the study included Drs. David O. Matson of the Center for Pediatric Research in Norfolk, Virginia; Mary Allen Staat of Cincinnati Children's Hospital in Ohio; Parvin Azimi of Children's Hospital of Oakland, Oakland, California and Berkeley Bennett and Pedro A. Piedra of BCM.
Funding for this study came from by National Institutes of Health (NIH), the U.S. Department of Veterans Affairs, the Gulf Coast Digestive Disease Center, the United States Public Health Service, Glaser Pediatric Research Network Fellowship Award and an inter-institutional grant from Wyeth-Lederle Vaccines and Pediatrics.