What you carry at this position in your DNA and what research says about it.
Norovirus and Gut Health: 8/10 evidence, 14 publications.
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Sample genotype (not yours): A/A
Typical Stomach Flu Susceptibility
You are a genetic secretor, meaning you express blood group antigens in bodily fluids. This makes you susceptible to common norovirus strains but keeps your risk for gallstones and ulcers at baseline.
What this genotype means: Typical susceptibility to norovirus; Baseline risk of gallstones and gastric ulcers.
Sample genotype (not yours): A/T
Carrying one copy of the secretor allele is sufficient to express mucosal antigens. You remain susceptible to norovirus and maintain typical baseline risks for digestive issues.
Sample genotype (not yours): T/T
Norovirus Resistance but Higher Gallstone Risk
You are a genetic non-secretor, which provides strong resistance to the stomach flu. However, this status is linked to an increased risk of gallstones and gastric ulcers.
What this genotype means: Strong resistance to common norovirus strains; Increased risk of gallstones and gastric ulcers; Altered vitamin B12 absorption.
Gene function and biological role
Gene Function: The FUT2 gene encodes the fucosyltransferase 2 enzyme, which is responsible for producing the H antigen, a precursor of ABO blood group antigens, in bodily secretions and on mucosal surfaces [1]. Individuals with a fully functional FUT2 gene are known as secretors, meaning they express these blood group antigens in their saliva, gastrointestinal tract, and other fluids [1]. Conversely, individuals with non-functional FUT2 variants are classified as non-secretors because they lack these mucosal antigens [1]. This secretor status plays a profound role in shaping the gut microbiome, modulating susceptibility to various viral and bacterial pathogens, and influencing inflammatory processes in the digestive tract [2].
Variant Impact: The rs1047781 variant is a missense mutation in the FUT2 gene, resulting in an isoleucine to phenylalanine amino acid change at position 140 of the protein [1]. The T allele represents the inactive or non-secretor version of the gene, which is highly prevalent in East Asian populations but virtually absent in Caucasians [1]. Having two copies of the T allele leads to a complete lack of blood group antigens on mucosal surfaces, rendering the individual a non-secretor [1]. This molecular change alters how the gut interacts with pathogens and has been linked to distinct metabolic and disease risks [3].
Key Insight: While being a non-secretor provides near-complete genetic immunity to the most common strains of norovirus, it simultaneously increases the risk of developing gallstones and gastric ulcers.
Location: FUT2. Chromosome 19 · 19q13.33 · 48.7 Mb
Estimated prevalence by population
Global 97.3%; European 99.9%; African 99.8%; East Asian 30.7%; South Asian 96.2%; Americas 99.3%; Ashkenazi 99.8%; Finnish 100.0%; Middle Eastern 100.0%; Amish 100.0%.
Estimated AA genotype frequency.
Global 2.0%; European 0.1%; African 0.2%; East Asian 49.4%; South Asian 3.7%; Americas 0.7%; Ashkenazi 0.2%; Finnish 0.0%; Middle Eastern 0.0%; Amish 0.0%.
Estimated AT genotype frequency.
Global 0.7%; European < 0.1%; African < 0.1%; East Asian 19.9%; South Asian < 0.1%; Americas < 0.1%; Ashkenazi < 0.1%; Finnish 0.0%; Middle Eastern 0.0%; Amish 0.0%.
Estimated TT genotype frequency.
Showing effects for A/A genotype
Immunity & Inflammation
Infection Susceptibility & Resistance
Norovirus Resistance. Evidence: 3/10. Source: PMID 8621666. Typical Susceptibility.
Organ Systems
Digestive & Gut Disorders
Gallstones. Evidence: 8/10. Source: PMID 34594039. Typical Risk.
Gastric Ulcer. Evidence: 7/10. Source: PMID 34594039. Typical Risk.
Nutrition & Metabolism
Vitamin & Mineral Metabolism
Vitamin B12 Levels. Evidence: 6/10. Source: PMID 22367966. Typical Levels.
Showing effects for A/T genotype
Showing effects for T/T genotype
Norovirus Resistance. Evidence: 3/10. Source: PMID 8621666. Highly Resistant.
Gallstones. Evidence: 8/10. Source: PMID 34594039. Increased Risk.
Gastric Ulcer. Evidence: 7/10. Source: PMID 34594039. Increased Risk.
Vitamin B12 Levels. Evidence: 6/10. Source: PMID 22367966. Altered Levels.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Having two copies of the A allele means you have a fully functional FUT2 gene and are classified as a secretor [1]. Your body secretes blood group antigens into your saliva and digestive tract, which acts as the primary binding site for norovirus, making you susceptible to the typical stomach flu [1]. However, this active secretion helps maintain a healthy mucosal barrier, keeping your risk for gallstones and gastric ulcers at the typical population baseline [2]. Your levels of certain digestive enzymes and metabolic biomarkers are also expected to be typical [2].
Typical susceptibility to norovirus; Baseline risk of gallstones and gastric ulcers.
Sample genotype: AT (Heterozygous)
Having one copy of the T allele does not significantly alter your secretor status, as the secretor trait is dominant [1]. You still produce functional fucosyltransferase 2 enzymes and express blood group antigens on your mucosal surfaces [1]. Consequently, you remain susceptible to norovirus infections because the virus can still bind to your gut lining [1]. On the positive side, your risk of developing gallstones, gastric ulcers, and other inflammatory gastrointestinal conditions remains at the typical baseline [2].
Sample genotype: TT (Homozygous)
Carrying two copies of the T allele makes you a genetic non-secretor, a status found in about fifteen percent of East Asian populations [1]. Because you do not express blood group antigens on your gut lining, the most common strains of norovirus cannot bind to your cells, giving you strong resistance to the stomach flu [1]. However, this lack of mucosal antigens alters your gut environment and bile composition, which significantly increases your risk of developing gallstones [2] and gastric ulcers [2]. Additionally, this genotype is associated with lower levels of certain blood enzymes and altered vitamin B12 absorption [3].
Strong resistance to common norovirus strains; Increased risk of gallstones and gastric ulcers; Altered vitamin B12 absorption.
Variants with shared genetic architecture
rs516246 · FUT2 Gene · Chr 19 · Gut Health and Immunity
rs602662 · FUT2 Gene · Chr 19 · Vitamin B12 and Gut Health
rs492602 · FUT2 Gene · Chr 19 · Cholesterol and Gut Health
FUT2 Variants Confer Susceptibility to Familial Otitis Media.
A cross-population atlas of genetic associations for 220 human phenotypes.
Content updated August 2026.
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