Scientists uncover how a prehistoric FUT2 gene variant protects some people from Norovirus.
A new genetic study has revealed why some people seem naturally immune to winter vomiting disease, an illness caused by the highly contagious Norovirus. The infection often spreads during the colder months, sweeping through schools, workplaces, and households with alarming speed. While most people recover after a few unpleasant days of nausea, cramps, and exhaustion, others never get sick at all—no matter how much exposure they have. Researchers from Karolinska Institutet in Sweden have found that Norovirus resistance traces back thousands of years to a single genetic variation.
The discovery centers on a gene called FUT2. Normally, FUT2 produces an enzyme in the intestinal lining that attaches certain sugar molecules to the surface of gut cells. The Norovirus uses these sugars as landing sites to invade and infect the body. But some people carry a version of the FUT2 gene that doesn’t work properly. In these individuals, the enzyme never completes its task, leaving the cell surface bare. Without those sugars, the virus has nowhere to attach—and infection simply doesn’t happen. This defective version of FUT2, while seemingly minor, acts as a genetic shield against one of the most common and disruptive stomach illnesses in the world.
Researchers traced the gene’s spread by analyzing DNA from more than 4,000 ancient human remains spanning the last 10,000 years. Their findings show that early farmers from what is now Turkey brought the protective gene to Europe around 6,000 BCE. As agriculture spread and population density increased, contagious diseases like Norovirus became more common. In that environment, having the defective FUT2 gene became a major advantage, allowing those who carried it to avoid repeated illness and continue working, eating, and caring for their communities while others were bedridden. Over thousands of years, the gene variant became far more widespread in European populations.
Modern evidence supports the same pattern. By studying genetic data from over 700,000 people, scientists confirmed that those with two copies of the defective FUT2 gene (i.e., one from each parent) had higher levels of Norovirus resistance. Even when exposed to outbreaks, these individuals often remained unaffected. Laboratory experiments helped confirm the finding. Scientists grew miniature versions of human intestines, known as gut organoids, from tissue samples. When exposed to the virus, organoids from people with the double variant showed no infection at all, proving that the mutation offers full protection.
While this might sound like an evolutionary jackpot, the gene’s benefits come with a trade-off. People carrying the FUT2 mutation are more likely to experience certain digestive issues, such as gallstones and stomach ulcers. Researchers believe these problems are linked to how the mutation alters the gut’s chemical makeup. In ancient times, when diets were lower in fat and daily stress levels were different, these risks likely mattered less. In today’s environment, the same genetic trait that once protected communities from stomach viruses can increase the chance of other health concerns.
Scientists involved in the project said that understanding how such mutations evolved helps explain modern patterns of disease resistance like Norovirus resistance, and vulnerability. The findings also show how genetic changes shaped by ancient environments can continue to influence human health in unexpected ways. While the mutation is not something that can be developed or removed, its discovery provides a clearer look at how evolution equipped humans to survive changing conditions.
The research team, which included scientists from Linköping University and the Max Planck Institute for Evolutionary Anthropology, published the study in Molecular Biology and Evolution. The work was supported by several Swedish and European scientific foundations. Approximately one in five Swedes today carry two copies of the protective FUT2 gene, meaning a significant portion of the population is naturally resistant to Norovirus. For those without the mutation, the usual advice still stands—wash hands often, avoid sharing food during outbreaks, and stay home when sick. But for the lucky few, evolution has already written a permanent line of defense into their DNA.
Sources:
Study unravels the genetic shield against winter vomiting disease
Natural Selection of a Virus-Protective FUT2 Variant Following the Transition to Agriculture
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