A “stomach bug” is the common name for acute gastroenteritis, which is an infection of the stomach and intestines causing symptoms like vomiting, diarrhea, and stomach cramps. The most frequent causes are viruses, particularly norovirus, which accounts for approximately half of all viral gastroenteritis cases, and rotavirus, which is a common cause in children. While the traditional and most frequent routes of infection are well-established, scientific evidence suggests that certain stomach viruses can indeed spread through the air under specific circumstances.
Common Ways Gastroenteritis Spreads
The primary mode of transmission for most gastroenteritis-causing pathogens is the fecal-oral route, which involves the ingestion of microscopic particles of feces from an infected person. This occurs when poor hand hygiene allows the virus to move from an infected person’s stool to their hands and then to surfaces, food, or directly to another person’s mouth. Norovirus is highly contagious because it only takes a very small number of viral particles, possibly as few as 18, to cause an infection.
Contaminated food and water also represent a transmission pathway, commonly referred to as foodborne illness. Food can become contaminated if it is handled by an infected person who has not washed their hands properly, or if it is grown or harvested in contaminated water. Outbreaks often occur when shellfish are consumed raw or undercooked, or when produce is not washed well before consumption.
Viruses can easily be transferred via fomites, which are inanimate objects or surfaces. Doorknobs, light switches, utensils, and shared electronic devices can harbor infectious particles that are then picked up on hands. Because many of these viruses are environmentally stable, they can survive on surfaces for extended periods, making secondary transmission from these objects a threat.
Understanding Aerosolized Transmission
True airborne diseases, like measles, involve pathogens that can remain suspended in the air for long periods and travel over long distances on air currents. Gastroenteritis viruses, however, primarily spread through aerosols or droplets generated during specific, forceful events, which is distinct from true airborne transmission.
The most significant event that generates infectious aerosols is forceful vomiting. When a person with norovirus vomits, the pressure atomizes viral particles, creating a cloud of microscopic droplets containing the virus. These bioaerosols can be small enough, less than 5 micrometers, to remain briefly suspended in the air and travel short distances, where they can be inhaled by others nearby. Studies have detected norovirus RNA in air samples following a vomiting event, with higher concentrations observed when the event occurred more recently.
Another mechanism for aerosol generation is the toilet plume created when a contaminated toilet is flushed. The forceful action of flushing water aerosolizes viral particles present in the bowl, propelling them up to five feet into the air. While these particles settle relatively quickly compared to a truly airborne pathogen, they can contaminate nearby surfaces like toothbrushes, towels, and the floor. Using a communal bathroom during an outbreak can increase the risk of exposure, even without direct contact with an infected person.
Although aerosol transmission is considered a less common route than direct contact or contaminated food, it is a recognized factor in outbreaks, particularly in semi-enclosed settings like hospitals or cruise ships. The presence of viral particles in very small, submicrometer sizes indicates that inhalation of these aerosols is a plausible mechanism of infection.
Protecting Yourself and Others
Effective hand hygiene is the primary defense against the spread of gastroenteritis, regardless of the transmission route. Hands should be washed often with soap and running water for at least 20 seconds, especially after using the toilet and before handling food. Alcohol-based hand sanitizers are not reliably effective against non-enveloped viruses like norovirus and should not be used as a substitute for thorough handwashing.
Disinfection of contaminated surfaces minimizes the risk from both surface contact and settled aerosols. Surfaces contaminated with vomit or feces should be cleaned immediately with a chlorine bleach solution. A concentration of 1,000 to 5,000 parts per million (ppm) of sodium hypochlorite is recommended. This is achieved by mixing 5 to 25 tablespoons of household bleach into a gallon of water. The solution should be left on the surface for at least five minutes to inactivate the viruses before rinsing.
During active illness, minimizing the generation and spread of infectious aerosols is helpful. When using the toilet, closing the lid before flushing helps reduce the toilet plume and contamination of the bathroom environment. Contaminated laundry, such as clothing or linens soiled with vomit or stool, should be removed carefully to avoid shaking particles into the air. These items should be washed with detergent at the maximum available cycle length and dried at the highest heat setting.