The common reovirus—usually considered harmless in humans other than causing diarrhea in infants—in fact affects the immune system, and "sets the stage for an autoimmune disorder, and for celiac disease in particular," says Bana Jabri from the University of Chicago.
People who are infected with the reovirus in their first year of life, when their immune system is still maturing, are the most likely to develop celiac disease, especially if they're weaned off breastfeeding in the first six months, and solids that include gluten are introduced.
One clue that Jabri and her research team discovered was that celiacs have much higher levels of antibodies against reoviruses, which means they suffered an infection at some time, and they also had more genetic markers that regulate our tolerance to gluten.
Celiac disease affects one in 133 people, but it's reckoned that just 17 per cent of cases are ever identified. The disease is an 'improper' immune response to gluten, a protein found in wheat, rye and barley, and it damages the lining of the small intestine. A strict gluten-free diet is the only known treatment.