The Spread of Norovirus and Precautions Needed to Prevent It
Published 2019-02-19
The norovirus is a highly contagious virus that causes stomach pain, vomiting and diarrhea. It is sometimes called the “stomach flu” and was first observed in 1972.7 Since then, it has been the subject of many studies and news reports due to its rapid onset and intense symptoms. A major concern related to the virus is the rate at which it can be transmitted from person to person.
The virus is thought to be the most common cause of acute gastroenteritis (diarrhea and vomiting), causing around 20 million cases in the US each year.7 Almost half of all food-related outbreaks in the US are believed to be caused by noroviruses.6 Considering how common it is and how easily it spreads, those charged with managing high-traffic or high-density facilities must consider ways to kill norovirus in order to prevent costly outbreaks.
How the Spread of Norovirus Happens
A person can get norovirus from having direct contact with an infected person, consuming contaminated food or water, or by touching contaminated surfaces and putting unwashed hands in their mouth.1 The virus is transmitted through the air as well.6b Only a few contaminated particles must be ingested for a person to become ill, which is one reason the norovirus is so contagious. Persons are especially contagious when they experience vomiting and diarrhea.1 A person infected with norovirus may be contagious two weeks or more after symptoms subside, which means well-intentioned hosts can cause infection when they feel well.5 Infected food workers are the cause of about 70% of outbreaks in the US.1 Many transfers from person to person occur after a person carrying the virus touches raw food with bare hands.1
The norovirus becomes airborne, or aerosolizes, when an infected person vomits.7 The aerosolized virus particles can then enter another person’s mouth and cause infection.8 The particles can also travel and contaminate surfaces such as door handles and tabletops.8 It can be difficult to exterminate the virus since contamination spreads easily.
Université Laval conducted a study in 8 hospitals and long-term care facilities and found norovirus particles in the air in 6 of them. Viruses were detected in 54% of the rooms housing patients with gastroenteritis, 38% of the hallways leading to their rooms, and 50% of nursing stations. Virus concentrations ranged from 13 to 2,350 particles per cubic meter. 20 particles are enough to cause symptoms.9 Clearly, patients and staff at facilities like hospitals and doctors’ offices are exposed to significant risk when appropriate measures haven’t been taken to prevent contagion.
Of the most prolific outbreaks of norovirus, many occur in public places such as restaurants, casinos and event venues. Some of the stories report horrific rates of infection. Close to 50% of attendees contract the virus, in some cases.2 Many of the events are referred to as “norovirus outbreaks.”
Outbreaks in the News
Much of the buzz around the norovirus focuses on outbreaks that occurred on cruise ships. Those outbreaks account for only about 1% of total reported outbreaks, however.1 Outbreaks happen everywhere. Of course, the virus tends to spread to more people in areas where the population is dense.
In a 1998 incident in the UK, a restaurant guest who was attending a party vomited onto the floor. The mess was promptly cleaned with a mop and disinfectant. Still, 56 of 126 people who attended the party started feeling norovirus symptoms during the following week.2 That means 44% of the group fell ill. The incident has been studied extensively since it happened, with cooperation from the British authorities.2
In the summer of 2018, a major outbreak of the norovirus in Las Vegas was reported. It occurred at the Westgate Hotel and Casino and was investigated by the Southern Nevada Health District, which confirmed the illness was consistent with norovirus after surveying 300 people.3 Similar outbreaks have occurred in other casinos, some of which caused hundreds of people to fall ill.3 For example, as many as 250 people contracted norovirus at the Flamingo Hotel and Casino in 2004.3 In 2011, more than 500 people in Las Vegas reported symptoms of sapovirus, which is similar to norovirus.3
One of the worst outbreaks of the norovirus happened at sea in early 2019. Aboard the Royal Caribbean Oasis of the Seas, 475 travelers were infected. The journey was called off only two days into a week-long vacation that would have included visits to Mexico and Jamaica.4 Although the majority of the passengers were not affected by the illness, their vacations were ruined. According to Royal Caribbean, one of the reasons the ship’s management ended the trip early was to give the crew time to completely sanitize the ship before the next cruise.4
Sanitize Surfaces and Air to Prevent the Spread of Norovirus
Well-known prevention methods such as frequent hand washing, resting at home when sick, and safe food preparation help to prevent the spread of norovirus. However, more can be done to prevent outbreaks. Measures designed only to limit direct contact with contaminated surfaces may not be enough, according to epidemiologist and researcher Caroline Duchaine.10 To kill norovirus, a strong defense strategy should include air purification with mobile or HVAC-mounted units.
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Sources
1. Preventing Norovirus Outbreaks. (June 2014). Retrieved February 1, 2019 from Norovirus informational article on CDC website.
2. Bloom, Josh (March 10, 2017). To Avoid Norovirus, Keep Your Distance – Especially in Restaurants. Retrieved February 1, 2019 from Norovirus article American Council on Science and Health.
3. Callahan, Bryan. (July 2, 2018). Update: 300 Respond to Survey After Apparent Norovirus Outbreak at Westgate. Retrieved February 1, 2019 from a news update on Norovirus outbreak in Las Vegas.
4. Ware, Gabriel (January 11, 2019). Norovirus Outbreak on Royal Caribbean Cruise Ships Sickens 475 Passengers. Retrieved February 1, 2019 from a news article on a Norovirus outbreak on a cruise ship.
5. (June 1, 2018). Transmission. In Norovirus (About Norovirus). Retrieved February 1, 2019 from a Norovirus transmission article on the CDC website.
6. Norovirus Outbreaks. Retrieved November 22, 2024 from a Norovirus informational article on the CDC website.
6b. How Norovirus Spreads. Retrieved November 22, 2024 from a Norovirus article on the CDC website.
7. Norovirus: Symptoms and Treatment. (January 28, 2019) Retrieved February 1, 2019 from an article on WebMD about Norovirus.
8. Shipman, Matt (August 19, 2015). Vomiting Device Offers First Direct Evidence that Vomit Aerosolizes Norovirus-Like Particles. Retrieved February 1, 2019 from an article on North Carolina State University news.
9. Bonifait, L., & Charlesbois, R., & Vimont, A., & Turgeon, N., & Veillette, M., & Longtin, Y., & Jean, J., & Duchaine, C. (2015) Detection and Quantification of Airborne Norovirus During Outbreaks in Healthcare Facilities. Clinical Infectious Diseases, 61, 299-304. Retrieved February 1, 2019 from an article on Norovirus in healthcare environments from Clinical Infectious Diseases.
10. Université Laval. (2015, April 30). Noroviruses spread several meters by air: Viruses responsible for 50 percent of gastroenteritis. ScienceDaily. Retrieved February 1, 2019 from an article on Science Daily about airborne Norovirus spread.
