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This is Scientific American’s 60-Second Science. I’m Karen Hopkin. This will just take a minute.

Crohn’s disease is a real pain in the gut¹. This inflammatory disorder² can lead to some serious intestinal³ difficulties. And heredity is partly to blame: some 30 different genes⁵ enhance susceptibility. But not everyone who has the genes gets Crohn’s.

Now scientists find that those with one type of risky⁶ gene⁴ may also need to catch a virus to trigger the disease. The results appear in the journal Cell.

Doctors have long suspected that some sort of virus might precipitate⁷ autoimmune disorders⁸, like lupus or multiple sclerosis. But in the case of Crohn’s, researchers stumbled across the connection by accident.

They were studying mice that carry a version of a gene associated with Crohn’s. These animals develop gut problems similar to those seen in humans. Then the researchers started keeping the animals in clean cages. Really clean cages, in which the bedding, food, and water are sterilized⁹. And the squeaky clean mice, even with the risky gene, stayed healthy. But when the scientists exposed the animals to a common virus, they came down with mouse Crohn’s.

The research shows that some illnesses may require a combination of genetic¹⁰ predisposition and infection, info that could lead to new treatment strategies.

Thanks for the minute for Scientific American’s 60-Second Science. I’m Karen Hopkin.