Human norovirus is a member of the Caliciviridae family of viruses which are single-stranded RNA nonenveloped viruses that cause acute gastroenteritis in humans. Norovirus was originally identified as Norwalk-like virus also referred to as small round structured viruses (SRSVs). Norovirus remains an enigma in many ways and is an important pathogen of human concern, responsible for the majority (50 %) of gastroenteritis outbreaks worldwide and for 90 % of all nonbacterial gastroenteritis outbreaks. Costs of emetic events from norovirus are vast. Their impact is difficult to estimate due to the fact that so many people are affected and many illnesses go unrecognized. Costs include lost wages from work, healthcare, epidemiological and environmental investigations, discarded food, and more. In 2012 the CDC estimated that each case of foodborne illness cost approximately $1,626 with an estimated yearly cost at $77.7 billion in the US.
A challenge in the prevention of illnesses caused by norovirus is the identification of those persons at risk. Outbreaks can occur in a wide variety of locations and can affect people of all ages. There are also several routes by which the virus can be transmitted including exposure to contaminated food resulting in person to person spread and secondary attacks. These factors make it difficult to identify the at risk population for norovirus infection, however; in a study conducted by the CDC from 1994-2006, 35.4 % of the laboratory confirmed cases of norovirus were from long-term care facilities, 31.1 % were from restaurants, parties, and events, 20.5 % were from vacation settings including cruise ships and resorts, and 13.0 % were from schools and communities. Studies such as these can help identify areas with higher risk for transmission.
A recent study performed by the Quebec Heart and Lung Institute demonstrates that one way norovirus is transmitted is through the air. The aerosolized particles can be found within up to several meters around the infected individual. This study was conducted within 8 hospitals and long-term care facilities within Canada where norovirus outbreaks were occurring. Samples were taken from the air with a distance of 1 meter from the doors of infected patient rooms and nursing stations. Virus particles were detected in the air in 6 out of the 8 facilities tested. They recovered virus from 54 % of patient rooms, 38 % of hallways and 50 % of nursing stations. They determined the viral concentration to range from 13 to 2,350 viral particles per meter of air. It is reported that as low as 20 virus particles are necessary to cause illness indicating that a person can potentially become infected with the virus if standing within 1 meter of the sampled locations.
Dr. Caroline Duchaine, who was the principal investigator in this study believes this research shows why norovirus is so hard to contain during an outbreak or emetic event. When staying on a cruise ship, dormitory, hotel resort or other places where people are housed it close quarters, it may not be such a bad idea to bring along a respiratory protection mask or even a mobile air filtration device to use in the occurrence of an outbreak or emetic event.
Sources: CDC, Food Safety News, Gastroenterology and Endoscopy News, WHO
I am a postdoctoral researcher with interests in pre-harvest microbial food safety, nonthermal food processing technologies, zoonotic pathogens, and plant-microbe interactions. My current research projects involve the optimization of novel food processing technologies to reduce the number of foodborne pathogens on fresh produce. I am a food geek!