Norovirus is the virus responsible for “winter vomiting bug” (as it’s called in the United Kingdom) or the “stomach flu” as it is called in the United States. Strict word nerds will tell you that “stomach flu” is a misnomer. The genus name Norovirus is derived from Norwalk virus, the only species of the genus. Norwalk-like viruses (NLVs) are a group of closely related and highly infectious viruses which were first reported following an outbreak of gastroenteritis in Norwalk, Ohio in 1972. The species causes approximately 90% of epidemic nonbacterial outbreaks of gastroenteritis around the world, and may be responsible for 50% of all foodborne outbreaks of gastroenteritis in the United States, according to the CDC.
Noroviruses are transmitted directly from person to person and indirectly via contaminated water and food. Outbreaks are most common between November and March.
Scientists have estimated that over 30 million virus particles can be “liberated” during vomiting, compared to an infectious
dose of 10–100 particles. In other words, as little a 10 virus particles might infect a person, and when someone vomits there are over 30 million virus particles available for attack.
In one study, transmission of the virus was studied in an outbreak in a hotel after a kitchen assistant at a North Yorkshire hotel vomited into a sink which was later used to prepare potato salad. The sink was cleaned with a chlorine based disinfectant and used the next morning to prepare the potato salad, subsequently identified as the “vehicle of infection.” A wedding reception at the North Yorkshire hotel was followed by an “explosive outbreak of gastroenteritis.” The attack rate among the 111 guests was 50% and “vomiting was a predominant feature.” The conclusion of the study pointed out the relative resistance of SRSVs to environmental disinfection and decontamination. SRSV or “small round structured virus” is another name for the norovirus.
In another study, six parties of diners, totaling 126 people, attended an evening dinner at a large hotel on Monday, December 7, 1998. In addition a number of hotel residents and casual diners were using a restaurant in a separate room on that evening. At 8.30 p.m., during the meal, a lady in one party vomited onto the polished wooden floor. The vomiting was not projectile and none of it was thought to have made contact with the table. She had not been ill prior to the meal, and had little warning that she was going to vomit. The vomitus was rapidly cleaned up by one of the waiters with a mop and disinfectant and the meal continued.
The vomitus was rapidly cleaned up by one of the waiters with a mop and disinfectant and the meal continued.
On the morning of Thursday, December 10, 1998, the organizer of the largest party contacted the local Environmental Health Department and reported that she was aware of nine members of her party of 45 who had become ill with vomiting, diarrhea and abdominal pain, mostly with an onset approximately 36 hours after the meal. That afternoon a further report was received from another party that a number of their members had become ill following the meal. The illness lasted approximately 24–48 hours in most people.
Only one member of the Dining Room staff became ill on December 8, 1998 with an illness similar to that of the diners which lasted 24 hours. The study didn’t mention whether it was the waiter that cleaned up the vomit was the one that got sick. The research report commented that it is possible that airborne transmission to the waiting staff was reduced due to the intermittent nature of their occupation of the dining room, but that the diners would be exposed continuously to the atmosphere in the dining room. However, the researchers added, it remains possible that aerosolization of virus particles led to contamination of food and/or hands and subsequent ingestion of the virus.
There researchers were able to summarize the following data on the diners. Eighty-three of the 126 guests returned completed questionnaires (response rate 66%). Fifty-two of the 83 responders reported illness (attack rate of 63%), of whom 43 (83%) suffered from either diarrhea or vomiting or both.
None of the diners in the other room became ill.
From statistical analysis, no food served at the dinner could be implicated as the vehicle for transmission of the virus.
Current Norovirus Status for 2016-2017
Currently, suspected and confirmed Norovirus Outbreaks have been reported by state health departments in Massachusetts, Michigan, Minnesota, Ohio, Oregon, South Carolina, Tennessee, Virginia, and Wisconsin to the National Outbreak Reporting System (NORS) by Week of Illness Onset. These are also the only states that participate in the NoroSTAT reporting system. Illinois does not participate, and the Illinois Department of Public Health has no mention of norovirus on their official website dph.illinois.gov.
The chart for participating states show that December 2016 was worse than December 2015, but not as bad as December 2012. Last year’s 2015-2016 norovirus season was the worst during March 2016, which was worse than another period since the NoroSTAT reporting system was operating.
Preventing Norovirus Infection
Norovirus is rapidly inactivated by either sufficient heating or by chlorine-based disinfectants and polyquaternary amines, but the virus is less susceptible to alcohols and detergents.
Practice proper hand hygiene, according to the Centers for Disease Control
Wash your hands carefully with soap and water especially after using the toilet and changing diapers, and always before eating, preparing, or handling food.
Noroviruses can be found in your vomit or stool even before you start feeling sick. The virus can stay in your stool for 2 weeks or more after you feel better. So, it is important to continue washing your hands often during this time, especially to prevent spreading the virus to other people.
Alcohol-based hand sanitizers can be used in addition to hand washing. But, they should not be used as a substitute for washing with soap and water.
Be aware that noroviruses are relatively resistant. They can survive temperatures as high as 140°F and quick steaming processes that are often used for cooking shellfish.
Wash fruits and vegetables and cook seafood thoroughly.
Carefully wash fruits and vegetables before preparing and eating them. Cook oysters and other shellfish thoroughly before eating them.
Food that might be contaminated with norovirus should be thrown out.
Keep sick infants and children out of areas where food is being handled and prepared.
When you are sick, do not prepare food or care for others who are sick.
You should not prepare food for others or provide healthcare while you are sick and for at least 2 days after symptoms stop. This also applies to sick workers in settings such as schools and daycares where they may expose people to norovirus.
Many local and state health departments require that food workers and preparers with norovirus illness not work until at least 48 hours after symptoms stop. If you were recently sick, you can be given different duties in the restaurant, such as working at a cash register or hosting.
Clean and disinfect contaminated surfaces
After vomiting or having diarrhea, immediately clean and disinfect contaminated surfaces. Use a chlorine bleach solution with a concentration of 1000–5000 ppm (5–25 tablespoons of household bleach [5.25%] per gallon of water) or other disinfectant registered as effective against norovirus by the Environmental Protection Agency (EPA).
Note: Evidence for efficacy of a cleaning agent against norovirus is usually based on studies using feline calicivirus (FCV)—a virus related to norovirus—as a surrogate. However, FCV and norovirus exhibit different physiochemical properties; thus, it is unclear whether inactivation of FCV by a specific cleaning agent reflects efficacy of such solutions against norovirus.
Wash laundry thoroughly
Immediately remove and wash clothes or linens that may be contaminated with vomit or stool (feces).
You should handle soiled items carefully without agitating them, wear rubber or disposable gloves while handling soiled items and wash your hands after, and wash the items with detergent at the maximum available cycle length then machine dry them.
Patterson W1, Haswell P, Fryers PT, Green J. Outbreak of small round structured virus gastroenteritis arose after kitchen assistant vomited. Commun Dis Rep CDR Rev. 1997 Jun 27;7(7):R101-3.
Marks PJ1, Vipond IB, Carlisle D, Deakin D, Fey RE, Caul EO. Evidence for airborne transmission of Norwalk-like virus (NLV) in a hotel restaurant. Epidemiol Infect. 2000 Jun;124(3):481-7.