Norovirus is a highly contagious pathogen, often called the “stomach bug” or “winter vomiting bug,” causing acute gastroenteritis with symptoms like sudden vomiting, diarrhea, nausea, and stomach cramps. Norovirus infections are widespread, affecting millions globally each year, making it a significant public health concern.
Understanding Norovirus Transmission
Norovirus primarily spreads through the fecal-oral route, meaning it is shed in the feces of infected individuals and then ingested by another person. Direct transmission occurs through person-to-person contact, such as shaking hands and then touching one’s own mouth. Indirect transmission is common when contaminated hands touch food, water, or surfaces. For instance, an infected person preparing food without proper handwashing can easily transfer the virus, leading to an outbreak.
Contaminated water sources, including municipal or recreational water, can also transmit norovirus. Shellfish, especially oysters, harvested from polluted waters can cause widespread illness if consumed raw or undercooked. The virus is resilient, surviving on surfaces for days or even weeks, facilitating spread in healthcare facilities, cruise ships, and schools. Fewer than 100 norovirus particles are sufficient to cause infection.
Airborne Transmission of Norovirus
While not typically classified as a respiratory virus like influenza or COVID-19, norovirus can become airborne through the aerosolized vomit particles. During forceful vomiting episodes, tiny viral droplets can be propelled into the air. These aerosols can settle on nearby surfaces or are inhaled by individuals in close proximity, leading to infection. This aerosolized spread is generally limited to a few feet from the source, making close contact during a vomiting incident a significant risk factor.
This mechanism differs from true airborne transmission, where pathogens remain suspended in the air over longer distances, as with measles or tuberculosis. Norovirus aerosols are heavier and tend to settle quickly, meaning the risk is highest immediately after a vomiting event and in the immediate vicinity. While the primary mode of transmission remains fecal-oral, understanding aerosolized vomit’s potential to spread highlights another infection pathway, especially in confined spaces. Recognizing this route is important for implementing effective control measures, particularly in outbreaks.
Preventing Norovirus Spread
Preventing norovirus spread involves a multifaceted approach, with rigorous hand hygiene being primary. Washing hands thoroughly with soap and water for at least 20 seconds is the most effective method, especially after using the restroom and before eating or preparing food. Alcohol-based hand sanitizers are less effective against norovirus, a non-enveloped virus, compared to enveloped viruses. Therefore, handwashing with soap and water is always preferred.
Thorough cleaning and disinfection of contaminated surfaces are also important, especially following any vomiting incidents. Norovirus can withstand many common disinfectants, so it is recommended that bleach-based cleaners are used for effective inactivation. A solution of 5 to 25 tablespoons of household bleach (5.25%–8.25%) per gallon of water is recommended for disinfecting surfaces. Contaminated items like clothing and bedding should be washed immediately with hot water and detergent.
Isolating infected individuals can help limit spread, particularly by preventing them from preparing food or caring for others while symptomatic and for at least 48 hours after symptoms resolve. Practicing safe food handling, such as thoroughly cooking shellfish and washing fruits and vegetables, also reduces the risk of foodborne transmission. These combined efforts significantly reduce the norovirus transmission risk.