Laboratory Evidence of Norwalk Virus Contamination on the Hands of Infected Individuals

Abstract

cHuman norovirus (NoV) outbreak investigations suggest that the hands of infected individuals play an important role in NoV transmission. However, there is no experimental evidence documenting the likelihood and degree of NoV contamination on hands. As part of a clinical trial designed to evaluate the efficacy of high-pressure processing for Norwalk virus (NV) inactivation in oysters, 159 hand rinse samples were collected from 6 infected and 6 uninfected subjects. NV was concentrated from the samples by polyethylene glycol precipitation, followed by RNA extraction using an automated guanidinium isothiocyanate-silica method. NV RNA was detected and quantified using multiple NV-specific reverse transcription-quantitative PCR (RT-qPCR) assays. A total of 25.4% (18/71) of the hand rinse samples collected from 6 infected volunteers were presumptively positive for NV, with an average of 3.86 log 10 genomic equivalent copies (GEC) per hand. Dot blot hybridization of PCR products obtained using a different primer set, and DNA sequencing of selected amplicons, provided further confirmation of the presence of NV in the hand rinses. NV contamination was also detected in two hand rinse samples obtained from one uninfected subject. These findings provide definitive evidence of NV contamination on the hands of infected subjects observed under controlled clinical research conditions. Such data support the need for better hand hygiene strategies to prevent NoV transmission. Human noroviruses (NoVs) are the most common cause of acute viral gastroenteritis worldwide (1) and a leading cause of food-borne disease (2, 3). They are spread primarily by the fecal-oral route but are also shed in vomitus. As such, NoV can be transmitted via consumption of fecally contaminated food or water or by contact with contaminated fomites and hands. The relative importance of each of these transmission routes is not well studied, but the potential for human hands to facilitate NoV transmission is widely recognized.A recent epidemiological study by the CDC (4) identified NoV as the predominant etiology of food-borne disease outbreaks, and the largest proportion of these outbreaks were associated with food handlers implicated as the source of contamination. Food handlers are of particular concern (5) because they may shed NoV at extremely high titers for days or weeks during a symptomatic or asymptomatic NoV infection and subsequently transfer viruses from their hands to food. Furthermore, both laboratory and epidemiological data (6-8) provide evidence that NoV may persist on hands and fomites for extended periods of time. For example, Malek et al. (9) described an outbreak of NoV infection in which the index case was an infected food handler who worked for a delicatessen meat supplier company and handled sliced delicatessen meat with bare hands 1 day after recovering from gastroenteritis symptoms. This investigation documented a clear association between the contaminated hands of the food handler and the subsequent NoV outbreak. Because of NoV-cont...

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