Norovirus is a highly contagious virus recognized as a leading cause of acute gastroenteritis, often referred to as the “stomach flu.” This common illness can spread rapidly in various settings, leading to widespread outbreaks of vomiting and diarrhea. Recent scientific investigations have uncovered an intriguing connection between an individual’s blood type and their likelihood of being infected by norovirus.
Blood Types and Norovirus Susceptibility
The susceptibility of individuals to norovirus infection is significantly influenced by a genetic trait known as “secretor status.” This status determines whether histo-blood group antigens (HBGAs) are expressed in bodily secretions like saliva and on the surface of cells lining the digestive tract. Secretors express these antigens, while non-secretors do not.
The presence or absence of these HBGAs on intestinal cells plays a large role in how norovirus interacts with the body. Many common strains of norovirus, particularly the prevalent GII.4 genotype, primarily infect secretors. Non-secretors often exhibit a strong innate resistance to these strains, and may not develop symptoms even if exposed.
While secretor status is a major factor, the specific ABO blood type can also play a role in susceptibility, although patterns can vary depending on the norovirus strain. Some studies suggest that individuals with O blood type may be more susceptible to prevalent norovirus strains compared to those with A, B, or AB blood types. Conversely, people with B blood type may show lower susceptibility to certain strains. Norovirus is a diverse group of viruses with many different strains, and each strain can have different binding preferences for HBGAs, meaning susceptibility can differ by strain.
How Norovirus Interacts with Blood Type Antigens
Histo-blood group antigens (HBGAs) are specific carbohydrate structures found on the surface of various cells throughout the body, including those that line the gastrointestinal tract, and are also present in bodily secretions. Norovirus particles use these HBGAs as binding sites to attach to and infect human cells.
The ability to express these HBGAs in secretions and on gut lining cells is largely controlled by the fucosyltransferase 2 (FUT2) gene. Individuals with a functional FUT2 gene are considered “secretors” because this gene enables the production of the enzyme that adds a fucose molecule to create the H antigen, a foundational HBGA. This H antigen, along with A or B antigens (depending on ABO blood type), provides the necessary binding sites for many norovirus strains, increasing susceptibility.
Conversely, individuals with a non-functional FUT2 gene are “non-secretors,” meaning they do not express these specific HBGAs on their gut lining or in their secretions. Without these binding sites, many norovirus strains cannot effectively attach to cells and initiate an infection, leading to a natural resistance for these individuals.
Practical Implications for Prevention
While an individual’s blood type and secretor status can influence their susceptibility to certain norovirus strains, these genetic factors do not provide complete immunity. Even those with a genetic predisposition to resistance can still become ill from other norovirus strains or if exposed to a very high viral load. Therefore, universal prevention methods remain the most effective strategy for everyone, regardless of their blood type or secretor status.
Hand hygiene is crucial for preventing norovirus transmission. This includes washing hands thoroughly with soap and water for at least 20 seconds, especially after using the restroom, changing diapers, and before preparing or eating food. Alcohol-based hand sanitizers are generally not as effective against norovirus and should not be relied upon as a substitute for hand washing.
Proper food handling and preparation are also important to prevent the spread of norovirus. This involves rinsing fruits and vegetables, and thoroughly cooking shellfish, such as oysters and clams, as they can sometimes be a source of contamination. If someone in the household is sick, it is advisable to avoid preparing food for others and to clean and disinfect contaminated surfaces with a bleach solution (e.g., 1 ½ cups of bleach per gallon of water) to kill the virus. Isolating sick individuals and immediately washing soiled clothing and linens in hot water further reduces widespread contamination.