A Model of Exposure to Rotavirus from Nondietary Ingestion Iterated by Simulated Intermittent Contacts

Abstract

Existing microbial risk assessment models rarely incorporate detailed descriptions of human interaction with fomites. We develop a stochastic-mechanistic model of exposure to rotavirus from nondietary ingestion iterated by simulated intermittent fomes-mouth, hand-mouth, and hand-fomes contacts typical of a child under six years of age. This exposure is subsequently translated to risk using a simple static dose-response relationship. Through laboratory experiments, we quantified the mean rate of inactivation for MS2 phage on glass (0.0052/hr) and mean transfer between fingertips and glass (36%). Simulations using these parameters demonstrated that a child's ingested dose from a rotavirus-contaminated ball ranges from 2 to 1,000 virus over a period of one hour, with a median value of 42 virus. These results were heavily influenced by selected values of model parameters, most notably the concentration of rotavirus on fomes, frequency of fomes-mouth contacts, frequency of hand-mouth contacts, and virus transferred from fomes to mouth. The model demonstrated that mouthing of fomes is the primary exposure route, with hand mouthing contributions accounting for less than one-fifth of the child's dose over the first 10 minutes of interaction.

Modeling of Human Viruses on Hands and Risk of Infection in an Office Workplace Using Micro-Activity Data

“…(2–5) The limited number of models results, in part, from the difficulty in obtaining the detailed activity data needed to generate quantified estimates of contact rates between hands and fomites, hands and mucus membranes, and fomites and mucus membranes. Measurements of contact rates are difficult because of the high frequency and relatively short duration of these activities.…”

“…Although they presented a hypothetical evaluation of their model by estimating the infection risk of influenza A in the workplace, they did not evaluate their model with empirical data. Similarly, Julian et al (2) presented a hypothetical evaluation of the micro-activity approach to assessing risk of rotavirus infection in daycare settings, but they also did not evaluate their model with experimental data. No previous studies were found in the literature reporting estimated pathogen loading on hands from contact with fomites evaluated with real-time environmental sampling.…”

Mouthing activity data for children aged 7 to 35 months in Taiwan

“…For estimating non-dietary ingestion exposures, quantified mouthing activity data of children thought to be important 3; 13; 15; 17–19 . In particular, these data are often used to estimate soil and/or dust ingestion rates and intake of chemicals from this exposure pathway 20–24 .…”

Quantified outdoor micro-activity data for children aged 7–12-years old

“…Mouthing and hand contact frequencies are key parameters for estimating non-dietary ingestion and dermal exposure (Zartarian et al, 2006;Nicas and Best, 2008;Stapleton et al, 2008;Julian et al, 2009;Schleier et al, 2009;Macedo et al, 2010;Tulve et al, 2010), as well as soil/dust ingestion rates (Ö zkaynak et al, 2010) critical for most hazardous site clean-up risk assessments including Superfund sites (US EPA, 2004). Several studies have quantified these mouthing and hand contact behaviors in children (Zartarian et al, 1997aBrinkman et al, 1999;Reed et al, 1999;Freeman et al, 2001Freeman et al, , 2005Tulve et al, 2002;AuYeung et al, 2004;Black et al, 2005;Auyeung et al, 2006;Beamer et al, 2008); however, we know of only one other study that has reported any data on children over 6 years of age (Freeman et al, 2001).…”