Article

Environmental transmission of norovirus gastroenteritis

Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, United States.
Current opinion in virology 02/2012; 2(1):96-102. DOI: 10.1016/j.coviro.2011.11.005
Source: PubMed

ABSTRACT The advent of molecular techniques and their increasingly widespread use in public health laboratories and research studies has transformed the understanding of the burden of norovirus. Norovirus is the most common cause of community-acquired diarrheal disease across all ages, the most common cause of outbreaks of gastroenteritis, and the most common cause of foodborne disease in the United States. They are a diverse group of single-stranded RNA viruses that are highly infectious and stable in the environment; both symptomatic and asymptomatic infections are common. Through shedding in feces and vomit, norovirus can be transmitted directly through an array of routes: person-to-person, food or the environment. The relative importance of environmental transmission of virus is yet to be fully quantified but is likely to be substantial and is an important feature that complicates control.

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    • "Illnesses associated with adenoviruses range from acute respiratory disease, pneumonia, conjunctivitis, and gastroenteritis, all of which could potentially be transmitted environmentally through non-potable uses of harvested stormwater (Arnone and Walling, 2007). Noroviruses are frequently reported as the leading cause of viral gastroenteritis outbreaks worldwide, with some literature estimating that they account for ~50% of all gastroenteritis cases (Lopman et al., 2012; Patel et al., 2009). Direct measurements of viral concentration in stormwater, however, are sparse due to the difficulties facing the quantification technologies, which are often plagued by poor recoveries in environmental water and inhibitory effects of PCR used for detecting viral genomes (Rajal et al., 2007). "
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    ABSTRACT: Capturing stormwater is becoming a new standard for sustainable urban stormwater management, which can be used to supplement water supply portfolios in water-stressed cities. The key advantage of harvesting stormwater is to use low impact development (LID) systems for treatment to meet water quality requirement for non-potable uses. However, the lack of scientific studies to validate the safety of such practice has limited its adoption. Microbial hazards in stormwater, especially human viruses, represent the primary public health threat. Using adenovirus and norovirus as target pathogens, we investigated the viral health risk associated with a generic scenario of urban stormwater harvesting practice and its application for three non-potable uses: 1) toilet flushing, 2) showering, and 3) food-crop irrigation. The Quantitative Microbial Risk Assessment (QMRA) results showed that food-crop irrigation has the highest annual viral infection risk (median range: 6.8×10(-4)-9.7×10(-1) per-person-per-year or pppy), followed by showering (3.6×10(-7)-4.3×10(-2)pppy), and toilet flushing (1.1×10(-7)-1.3×10(-4)pppy). Disease burden of each stormwater use was ranked in the same order as its viral infection risk: food-crop irrigation>showering>toilet flushing. The median and 95th percentile risk values of toilet-flushing using treated stormwater are below U.S. EPA annual risk benchmark of ≤10(-4)pppy, whereas the disease burdens of both toilet-flushing and showering are within the WHO recommended disease burdens of ≤10(-6)DALYspppy. However, the acceptability of showering risk interpreted based on the U.S. EPA and WHO benchmarks is in disagreement. These results confirm the safety of stormwater application in toilet flushing, but call for further research to fill the data gaps in risk modeling as well as risk benchmarks. Copyright © 2015 Elsevier B.V. All rights reserved.
    Science of The Total Environment 02/2015; 523:95-108. DOI:10.1016/j.scitotenv.2015.03.077 · 4.10 Impact Factor
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    • "The viruses are transmitted mainly through the fecal-oral route, including consumption of contaminated food and water [2] [3] [4]. Yet, numerous outbreaks occurring in public settings, such as cruise ships, nursing homes, hospitals, and daycare centers, strongly indicate that food is rarely the main vehicle; rather, high persistence, infectivity, and transmissibility collectively implicate contaminated surfaces as a main reservoir for the spread of NoVs [5] [6] [7]. Currently, strict compliance with hygiene practices such as the use of chemical disinfectants and hand washing is recommended to break the cycle of NoV transmission by inactivating or physically removing the virus particles from fomites or hands [8]. "
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    • "The main route of transmission in over 70% of outbreaks is person-to-person [7] thus favoring the occurrence of large outbreaks in semi-closed environments. The extensiveness of such outbreaks is explained by the low infectious dose of norovirus (18 virus particles are sufficient for infection), with shedding in stool for 20 to 40 days (also present in asymptomatic individuals) and by its long persistence in the environment (resistance to disinfectants, heating, freezing), up to two weeks on surfaces [17] [18] [19]. In addition, norovirus infections can occur repeatedly through life due to lack of complete cross-protection against the diverse norovirus strains and the lack of long-lasting immunity [10]. "
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