Heterogeneity in norovirus shedding duration affects community risk

Abstract

Norovirus is a common cause of gastroenteritis in all ages. Typical infections cause viral shedding periods of days to weeks, but some individuals can shed for months or years. Most norovirus risk models do not include these long-shedding individuals, and may therefore underestimate risk. We reviewed the literature for norovirus-shedding duration data and stratified these data into two distributions: regular shedding (mean 14-16 days) and long shedding (mean 105-136 days). These distributions were used to inform a norovirus transmission model that predicts the impact of long shedders. Our transmission model predicts that this subpopulation increases the outbreak potential (measured by the reproductive number) by 50-80%, the probability of an outbreak by 33%, the severity of transmission (measured by the attack rate) by 20%, and transmission duration by 100%. Characterizing and understanding shedding duration heterogeneity can provide insights into community transmission that can be useful in mitigating norovirus risk.

Norovirus prevalence and estimated viral load in symptomatic and asymptomatic children from rural communities of Vhembe district, South Africa

“…Similarly, Ayukekbong et al [34] reported that in developing countries NoV infections are very common with comparable detection rates observed in diarrhea cases and controls. However in a cross-sectional study, it is easy to mis-classify substantial numbers of post-symptomatic infections as asymptomatic infections even when the controls are defined as absence of diarrhea symptoms in the preceding 4 weeks [35], [36], [37].…”

Environmental Transmission of Human Noroviruses in Shellfish Waters

“…However, there is heterogeneity in the duration of shedding. Milbrath et al developed a NoV transmission model based on NoVshedding data and concluded that long-term (105-to 136-day) shedders increase the probability of an outbreak by 33% and the severity of transmission (as measured by the attack rate) by 20% (51). Therefore, knowledge of the duration of NoV shedding can help inform NoV risk management strategies.…”

Norovirus vaccines: Correlates of protection, challenges and limitations

“…64,65 Long-term shedding was described among children less than 6 months, 63 in elderly, 64 hospitalized and immunosuppressed patients. 62 Predictive modeling of viral shedding classifies shedding into regular shedding with a mean of 14-16 d and long shedding with a mean ranging between 105 and 136 d 66 Recent studies suggest the lack of a significant difference of virus shedding between asymptomatic and symptomatic NoV infections despite the individual variation in virus peak levels detected in stool. 67,68 This study reported different viral shedding activities as compared to previous reports 7,69 whereby infected adults shed virus during a range of 15-56 d. The authors argued that the variable results in NoV shedding might be due to the use of different PCR techniques to detect the virus.…”