Norovirus is a common and highly contagious cause of acute gastroenteritis, often called ‘stomach flu,’ though it is unrelated to influenza. This virus triggers sudden symptoms like vomiting, diarrhea, and stomach pain, typically lasting one to three days. Its rapid spread often raises questions about how it travels, particularly whether it can be airborne.
Primary Transmission Routes
Norovirus primarily spreads through the fecal-oral route, meaning the virus is ingested from contaminated feces or vomit. This occurs through direct contact with an infected person, such as caring for them or sharing utensils. The virus is shed in both stool and vomit, and it only takes a very small number of particles—as few as 18—to cause infection.
Contaminated food and water are also major transmission pathways. Food can become contaminated if handled by an infected person who has not washed their hands properly, or if it comes into contact with contaminated surfaces. Raw shellfish, such as oysters, are a frequent source of infection because they can concentrate viral particles from contaminated water. Drinking water can also be contaminated if a septic tank leaks into a well or if water treatment is inadequate.
Indirect contact with contaminated surfaces or objects, known as fomites, is another significant route. Norovirus is robust and can survive on surfaces for days or even weeks, acting as a persistent source of infection. This explains why outbreaks often occur in crowded environments like cruise ships, dormitories, and healthcare facilities, where surfaces are frequently touched.
Is Norovirus Truly Airborne?
The term ‘airborne transmission’ typically refers to pathogens that remain suspended in the air over long distances, like measles or tuberculosis. Norovirus does not spread in this manner. However, it can spread through aerosols generated from vomit or diarrhea. These aerosols are tiny droplets that can briefly travel through the air, landing on nearby surfaces or being inhaled.
When an infected person vomits, the force can atomize liquid containing viral particles, creating a cloud of fine droplets. These particles can be small enough to stay airborne for a short period. While inhaling these aerosolized particles can lead to infection, this is generally considered short-range droplet transmission rather than long-range airborne spread.
Research has detected norovirus in the air of healthcare facilities during outbreaks. This suggests that aerosolized viral particles, particularly from vomiting incidents, contribute to outbreaks. The virus’s ability to withstand aerosolization and remain infectious supports this localized airborne component of its transmission.
Stopping Norovirus in Its Tracks
Preventing norovirus spread relies on meticulous hygiene and sanitation practices. Thorough handwashing with soap and water is the most effective measure, especially after using the toilet, changing diapers, and before preparing or eating food. Alcohol-based hand sanitizers are not as effective against norovirus and should not be used as a substitute for washing with soap and water.
Cleaning and disinfecting contaminated surfaces immediately is paramount. A bleach solution is effective against norovirus and should be left on surfaces for at least five minutes before wiping. It is important to clean up visible vomit or stool before applying disinfectant, as organic matter can reduce the bleach solution’s potency.
Safe food handling practices are also important in preventing transmission. This includes washing fruits and vegetables and thoroughly cooking shellfish, such as oysters, to an internal temperature of at least 145°F, as quick steaming may not kill the virus. Individuals experiencing norovirus symptoms should avoid preparing food for others and stay home from work or school for at least 48 hours after symptoms have stopped.