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Link to Viruses in the Gut Sheds New Light on Irritable Bowel Disease

New evidence explains how viruses may be involved in inflammatory bowel disease, including Crohn’s disease and ulcerative colitis. 

The CDC estimates that one million Americans have these problems. These conditions cause severe damage to the gastrointestinal system, and surgery is often necessary to remove part of the bowel. This research is the first of its kind to associate bowel disease with changes in the virome (human viruses and their genes).

Researchers at Washington University School of Medicine think that viruses could be infecting the bacteria in the gut, and their results are just the “tip of the iceberg,” according to corresponding author, Dr. Herbert Virgin. In a news release, Dr. Virgin explained that “Much of the increased viral diversity in participants with inflammatory bowel diseases was in the form of bacteriophages, which are viruses that infect bacteria and can incorporate themselves into the bacteria’s genetic material.”

The study, published in Cell (Norman et al, 2015), found that people with inflammatory bowel diseases (IBD) have a wider assortment of viruses in their digestive system compared to healthy people. They compared the viral DNA of patients with Crohn’s disease or ulcerative colitis to healthy people living in the same area (Chicago, Los Angeles, or Cambridge, UK). They reported an inverse relationship between bacteria and viruses in the gut for people with IBD. As bacteria diversity goes down, which is typical for IBD, the viral diversity goes up.

The relationship between bacteria and viruses within the gut could have implications for other diseases like obesity, diabetes, and others. The authors suggest that the virome should be considered when evaluating conditions that involve changes in bacteria that live in the GI tract.

“We know that mutations in human genes affect the risk of inflammatory bowel diseases, and scientists also are exploring how bacterial genes may influence risk,” said Virgin. “Our results show that the virome’s potential effects on the gut also need to be a part of these investigations.”

This breakthrough could impact how doctors approach the management of inflammatory gastrointestinal conditions.


Jason M. Norman, Scott A. Handley, Megan T. Baldridge, et al. Disease-specific alterations in the enteric virome in inflammatory bowel disease. Cell, Jan. 29, 2015; 160(3): 447-460.

“Viruses may play unexpected role in inflammatory bowel diseases.” Washington University School of Medicine, news release, Jan. 22, 2015


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