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Environmental surveillance of surface contamination is an unexplored tool for understanding transmission of SARS-CoV-2 in community settings. We conducted longitudinal swab sampling of high-touch non-porous surfaces in a Massachusetts town during a COVID-19 outbreak from April to June 2020. Twenty-nine of 348 (8.3%) surface samples were positive for SARS-CoV-2 RNA, including crosswalk buttons, trash can handles, and door handles of essential business entrances (grocery store, liquor store, bank, and gas station). The estimated risk of infection from touching a contaminated surface was low (less than 5 in 10,000) by quantitative microbial risk assessment, suggesting fomites play a minimal role in SARS-CoV-2 community transmission. The weekly percentage of positive samples (out of n = 33 unique surfaces per week) best predicted variation in city-level COVID-19 cases with a 7-day lead time. Environmental surveillance of SARS-CoV-2 RNA on high-touch surfaces may be a useful tool to provide early warning of COVID-19 case trends.

Indirect exposure to waterborne viruses increases the risk of infection, especially among children with frequent hand-to-mouth contacts. Here, we quantified the transfer of one bacteriophage (MS2) and two enteric viruses (adenovirus and coxsackievirus) from liquid to skin. MS2, a commonly used enteric virus surrogate, was used to compare virus transfer rates in a volunteer trial to those obtained using human cadaver skin and synthetic skin. MS2 transfer to volunteer skin was similar to transfer to cadaver skin but significantly different from transfer to synthetic skin. The transfer of MS2, adenovirus, and coxsackievirus to cadaver skin was modeled using measurements for viruses attaching to the skin (adsorbed) and viruses in liquid residual on skin (unadsorbed). We find virus transfer per surface area is a function of the concentration of virus in the liquid and the film thickness of liquid retained on the skin and is estimable using a linear model. Notably, the amount of MS2 adsorbed on the skin was on average 5 times higher than the amount of adenovirus and 4 times higher than the amount of coxsackievirus. Quantification of pathogenic virus retention to skin would thus be overestimated using MS2 adsorption data. This study provides models of virus transfer useful for risk assessments of water-related activities, demonstrates significant differences in the transfer of pathogenic virus and MS2, and suggests cadaver skin as an alternative testing system for studying interactions between viruses and skin.IMPORTANCE Enteric viruses (viruses that infect the gastrointestinal tract) are responsible for most water-transmitted diseases. They are shed in high concentrations in the feces of infected individuals, persist for an extended period of time in water, and are highly infective. Exposure to contaminated water directly (through ingestion) or indirectly (for example, through hand-water contacts followed by hand-to-mouth contacts) increases the risk of virus transmission. The work described herein provides a quantitative model for estimating human-pathogenic virus retention on skin following contact with contaminated water. The work will be important in refining the contribution of indirect transmission of virus to risks associated with water-related activities.

Background: Schistosomiasis is a parasitic disease which is spread through skin contact with water containing Schistosoma cercariae. Drug treatment has been the main control method, but it does not prevent reinfection. The use of soap can be a complementary measure to reduce transmission. Therefore, this study investigates the quantitative effect of different soaps on the mortality of Schistosoma mansoni cercariae. Methodology: Four soaps including two powder soaps (Kleesoft and Omo) and two bar soaps (B29 and Rungu) which are used in a schistosomiasis-endemic Tanzanian village were studied. S. mansoni cercariae were exposed to powder soaps of 0 (control), 10, 50, 75, 100 and 1000 mg/L and to bar soaps of 0 (control), 100, 500 and 1000 mg/L. The highest concentration of 1000 mg/L was selected based on the laboratory-estimated average soap concentration during handwashing. Cercariae were observed under a microscope after 0, 5, 15, 30, 45 and 60 minutes of exposure to determine their survival. Conclusions: All four soaps can kill S. mansoni cercariae and this lethal effect was related to soap concentration and exposure time. At the highest concentration of 1000 mg/L, all cercariae were dead at 5 minutes post-exposure with two powder soaps and Rungu, while 100% cercarial death was achieved between 5 minutes to 15 minutes for B29. Almost all cercariae survived after being exposed to 10 mg/L powder soaps and 100 mg/L bar soaps for 60 minutes. Powder soaps were more lethal than bar soaps. Considering the widely varying concentrations of soap during real-world hygiene activities and the necessity for a very high soap concentration to eliminate all cercariae in a short 5-minute exposure, providing the efficacy of soap in preventing schistosomiasis becomes challenging. Future studies should investigate whether soap can influence alternative mechanisms such as creating a barrier to skin, thereby providing protection. Author summary: Schistosomiasis is a major public health problem in low-resource countries where there is insufficient access to safe water, sanitation and hygiene (WASH). Preventive chemotherapy with praziquantel has been the main control method, but it cannot protect against reinfection. With the increasing awareness of the importance of a multi-faceted control strategy, WASH has been recommended as one of the core strategic interventions for schistosomiasis control. The use of soap, one hygiene practice, might play a role in prevention by reducing human exposure to cercariae, thereby lowering the infection risk at transmission sites. However, to the best of our knowledge, there are no detailed guidelines on how to use soap to prevent schistosomiasis in endemic areas. Therefore, this study aimed to explore the efficacy of four commercial Tanzanian soaps against Schistosoma mansoni cercariae to understand soap lethality. The results provide scientific evidence of soap protection against schistosome cercariae and suggest that future studies should investigate other potential mechanisms by which soap may provide protection against cercariae (e.g. damaging them sufficiently to hinder penetration into the skin or protecting skin against cercarial penetration). [ABSTRACT FROM AUTHOR]