Although the number of illnesses resulting from indirect viral pathogen transmission could be substantial, it is difficult to estimate the relative risks because of the wide variation and uncertainty in human behavior, variable viral concentrations on fomites, and other exposure factors. The purpose of this study was to evaluate the micro-activity approach for assessment of microbial risk by adapting a mathematical model to estimate probability of viral infection from indirect transmission. To evaluate the model, measurements of phage loading on fomites and hands collected before and after implementation of a Healthy Workplace Project™ intervention were used. Parameter distributions were developed from this data, as well as for micro-activity rates, contact surface areas, phage transfer efficiencies, and inactivation rates. Following the Monte Carlo simulations (n=1,000), the estimated phage loading on hands was not significantly different from the loading of phage on hands measured in the experimental trials. The model was then used to demonstrate that the Healthy Workplace Project™ intervention significantly reduced risk of infection by 77% for rotavirus and rhinovirus. This is the first published study to successfully evaluate a model focused on the indirect transmission of viruses via hand contact with measured data and provide an assessment of the micro-activity approach to microbial risk evaluation.

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Viral illnesses like gastroenteritis and the common cold create a substantial burden in the workplace due to reduced productivity, increased absenteeism, and increased health care costs. Behaviors in the workplace contribute to the spread of human viruses via direct contact between hands, contaminated surfaces and the mouth, eyes, and/or nose. This study assessed whether implementation of the Healthy Workplace Project (HWP) (providing hand sanitizers, disinfecting wipes, facial tissues, and use instructions) would reduce viral loads in an office setting of approximately 80 employees after seeding fomites and the hands of volunteer participants with an MS-2 phage tracer. The HWP significantly reduced viable phage detected on participants’ hands, communal fomites, and personal fomites (p≤0.010) in office environments and presents a cost-effective method for reducing the health and economic burden associated with viral illnesses in the workplace.

Naegleria fowleri is a free-living amoeba found in waters in warmer regions that causes primary amoebic meningoencephalitis, a rare but almost universally fatal disease. The goal of this project was to assess the occurrence of N. fowleri and other thermophilic amoebae in 33 recreational surface waters across Arizona to determine if their presence could be correlated with seasonal or other environmental factors. First, 1-L grab samples were collected over two years and analyzed using polymerase chain reaction and amoebae viability. Seasonality was observed, with N. fowleri and thermophilic amoebae (20% and 30%, respectively) being detected more often in the winter and spring combined than in the summer and fall combined (7.9% and 9.5%, respectively). The spring and fall both had an average temperature of 18°C, yet had different occurrence data (18.2% versus 5.9% for N. fowleri, respectively; 27.3% versus 0% for viable amoebae, respectively). These results are in stark contrast to previous studies in which N. fowleri has been found almost exclusively during warmer months. Over the two-year study, N. fowleri was detected in six and thermophilic amoebae in eight of the 33 recreational water bodies. Five of these were lakes near Phoenix that tested positive for N. fowleri and thermophilic amoebae over multiple seasons. These lakes differed significantly (P ≤ 0.05) from the other 28 surface waters, with a lower average temperature in the spring, a higher temperature in the fall, a higher pH and turbidity in the summer, and a lower electro-conductivity in the spring. They also had lower Escherichia coli and heterotrophic bacteria levels during colder months. Future N. fowleri monitoring in Arizona should focus on these five lakes to further elucidate the factors that contribute to the low occurrence of this amoeba in the summer or which might explain why these lakes appear to be reservoirs for the organism.

Cell culture assays in various formats have been used to study the infectivity of Cryptosporidium spp. as well as to determine the infectivity of naturally occurring oocysts in water. Currently, cell culture assays for infectious Cryptosporidium spp. in water have largely been limited to practice in research laboratories. One obstacle to the routine use of Cryptosporidium cell culture assays for the analysis of water samples is the coordination of water sample collection and processing with readiness of cell culture monolayers. For most Cryptosporidium cell culture assays, monolayers are allowed to develop for 24 to 48 h to reach 80 to 100% confluence prior to inoculation. In this study, we used immunofluorescent assay microscopy to evaluate freshly confluent (2-day-old) and aged (8-to 67-day-old) HCT-8 cell monolayers for their ability to support Cryptosporidium parvum infection. HCT-8 monolayers as old as 67 days were clearly shown to support infection. In two of three experiments, aged monolayers (8-to 11-day-old and 11-to 22-day-old, respectively) developed the same number of C. parvum clusters of infection as freshly confluent monolayers. Results suggest that it may be possible to use cell monolayers from freshly confluent to 3 weeks old on hand for infectivity assays without having to schedule sample processing to coincide with development of freshly confluent monolayers. This would make Cryptosporidium cell culture assays much more feasible for water quality and utility laboratories.