Enhanced Hygiene Measures and Norovirus Transmission during an Outbreak

Abstract

Control of norovirus outbreaks relies on enhanced hygiene measures, such as handwashing, surface cleaning, using disposable paper towels, and using separate toilets for sick and well persons. However, little is known about their effectiveness in limiting further spread of norovirus infections. We analyzed norovirus outbreaks in 7 camps at an international scouting jamboree in the Netherlands during 2004. Implementation of hygiene measures coincided with an 84.8% (95% predictive interval 81.2%-86.6%) reduction in reproduction number. This reduction was unexpectedly large but still below the reduction needed to contain a norovirus outbreak. Even more stringent control measures are required to break the chain of transmission of norovirus.G astroenteritis is one of the most common causes of illness (1). Recent fi ndings indicate norovirus is the most common cause of gastroenteritis (2,3). Of all gastroenteritis outbreaks reported in the Netherlands during 2002, 54% were caused by norovirus (4). Norovirus is predominantly transmitted through the fecal-oral route, either indirectly through contaminated food or surfaces or directly from person to person (5). It can be transmitted through small infectious droplets (aerosols) after a vomiting episode (6,7) and can survive for a very long time in the environment (5,8). Most norovirus outbreaks are seen in settings where clusters of vulnerable, susceptible persons live closely together, such as nursing homes, hospitals, and daycare centers (4), and in settings in which turnover of susceptible persons is high, such as hotels and cruise ships (9,10).Norovirus infection can cause serious medical complications, such as dehydration, in persons with underlying illness (11). No antiviral treatment exists for norovirus infection, and although norovirus vaccines are in development (12), none are available yet. Early studies suggested that norovirus outbreaks could be contained by rapid implementation of enhanced hygiene measures, such as washing hands, thoroughly cleaning contaminated surfaces, avoiding contact between sick and healthy persons, and requesting caretakers and cleaning staff to wear gloves and aprons (13-16). However, in nursing homes or on cruise ships, norovirus can cause consecutive outbreaks, even after implementation of strict hygiene protocols (9,17,18). No quantitative estimates exist of the results of such enhanced hygiene measures on reducing further transmission of norovirus. To our knowledge, the effect of enhanced hygiene measures has not been investigated in randomized controlled trials or in statistical analyses of outbreaks.We investigated the effect of enhanced hygiene measures on reducing norovirus transmission during an outbreak. We measured the effectiveness of enhanced hygiene measures as the relative reduction in the reproduction number-defi ned as the average number of secondary cases caused by 1 typical case-in the absence of and after enhanced hygiene measures. The value of this reproduction number provides crucial information about transmissio...

Critical Review on the Public Health Impact of Norovirus Contamination in Shellfish and the Environment: A UK Perspective

“…Vulnerable people such as the elderly, immunocompromised or the very young can require additional care (Harris et al 2008). Outbreaks of NoV frequently occur in high-density settings such as care homes, hospitals, and cruise ships; however, outbreaks in restaurants, hotels, holiday camps and through consumption of contaminated drinking water are also commonplace (Heijne et al 2009; Werber et al 2009). …”

Norovirus

“…For example, Vega and colleagues, reviewing norovirus trends in the United States from 2009 to 2013, demonstrated that GII.4 was more likely to be associated with person-to-person transmission, especially in long-term-care facilities (LTCFs) and hospital settings, whereas GI.7 and GII.12 were more frequently associated with foodborne disease (103). The environmental durability of norovirus leads to persistence of the pathogen in clinical settings and other closed-space environments, thus complicating complete disinfection and allowing for recurrent outbreaks (104,105).…”

Quantifying the roles of vomiting, diarrhea, and residents vs. staff in norovirus transmission in U.S. nursing home outbreaks

“…This method, originally described by Wallinga and Teunis, requires only onset dates of all cases in the outbreak and knowledge of the probability distribution of the serial interval for the specific infectious disease [17]. We used a serial interval for norovirus derived from several large norovirus outbreaks in child daycare centers in Sweden with a gamma probability distribution, mean of 3.6 days, and standard deviation of 2.0 days [19]. We performed sensitivity analyses with mean serial intervals varying between 1.5 and 4.0 days in half day increments (S2 RMarkdown File).…”

“…We performed sensitivity analyses with mean serial intervals varying between 1.5 and 4.0 days in half day increments (S2 RMarkdown File). Details of the estimation procedure are available elsewhere [17,19,20]. Briefly, this method uses the difference in symptom onsets dates between cases and the probability distribution of the serial interval to calculate the relative likelihood that cases with earlier symptom onset dates infected cases with later symptom onset dates.…”