Highly socially vulnerable communities exhibit disproportionately increased viral loads as measured in community wastewater.

Wastewater surveillance has proven to be a useful tool for evidence-based epidemiology in the fight against the SARS-CoV-2 virus. It is particularly useful at the population level where acquisition of individual test samples may be time or cost-prohibitive. Wastewater surveillance for SARS-CoV-2 has typically been performed at wastewater treatment plants; however, this study was designed to sample on a local level to monitor the spread of the virus among three communities with distinct social vulnerability indices in Shreveport, Louisiana, located in a socially vulnerable region of the United States. Twice-monthly grab samples were collected from September 30, 2020, to March 23, 2021, during the Beta wave of the pandemic. The goals of the study were to examine whether: 1) concentrations of SARS-CoV-2 RNA in wastewater varied with social vulnerability indices and, 2) the time lag of spikes differed during wastewater monitoring in the distinct communities. The size of the population contributing to each sample was assessed via the quantification of the pepper mild mottle virus (PMMoV), which was significantly higher in the less socially vulnerable community. We found that the communities with higher social vulnerability exhibited greater viral loads as assessed by wastewater when normalized with PMMoV (Kruskal-Wallis, p < 0.05). The timing of the spread of the virus through the three communities appeared to be similar. These results suggest that interconnected communities within a municipality experienced the spread of the SARS-CoV-2 virus at similar times, but areas of high social vulnerability experienced more intense wastewater viral loads.

Estimating Infection Risks and the Global Burden of Diarrheal Disease Attributable to Intermittent Water Supply Using QMRA.

Intermittent water supply (IWS) is prevalent throughout low and middle-income countries. IWS is associated with increased microbial contamination and potentially elevated risk of waterborne illness. We used existing data sets to estimate the population exposed to IWS, assess the probability of infection using quantitative microbial risk assessment, and calculate the subsequent burden of diarrheal disease attributable to consuming fecally contaminated tap water from an IWS. We used reference pathogens Campylobacter, Cryptosporidium, and rotavirus as conservative risk proxies for infections via bacteria, protozoa, and viruses, respectively. Results indicate that the median daily risk of infection is an estimated 1 in 23 500 for Campylobacter, 1 in 5 050 000 for Cryptosporidium, and 1 in 118 000 for rotavirus. Based on these risks, IWS may account for 17.2 million infections causing 4.52 million cases of diarrhea, 109 000 diarrheal DALYs, and 1560 deaths each year. The burden of diarrheal disease associated with IWS likely exceeds the WHO health-based normative guideline for drinking water of 10-6 DALYs per person per year. Our results underscore the importance water safety management in water supplies and the potential benefits of point-of-use treatment to mitigate risks.

Environmental DNA (eDNA) removal rates in streams differ by particle size under varying substrate and light conditions.

The use of environmental DNA (eDNA) as a sampling tool offers insights into the detection of invasive and/or rare aquatic species and enables biodiversity assessment without traditional sampling approaches, which are often labor-intensive. However, our understanding of the environmental factors that impact eDNA removal (i.e., how rapidly eDNA is removed from the water column by the combination of decay and physical removal) in flowing waters is limited. This limitation constrains predictions about the location and density of target organisms after positive detection. To address this question, we spiked Common Carp (Cyprinus carpio) eDNA into recirculating mesocosms (n = 24) under varying light (shaded versus open) and benthic substrate conditions (no substrate, bare substrate, and biofilm-colonized substrate). We then collected water samples from each mesocosm at four time points (40 min, 6 h, 18 h, and 48 h), and sequentially filtered the samples through 10, 1.0, and 0.2 µm filters to quantify removal rates for different eDNA particle sizes under varying light and substrate conditions. Combining all size classes, total eDNA removal rates were higher for mesocosms with biofilm-colonized substrate compared to those with no substrate or bare (i.e., no biofilm) substrate, which is consistent with previous findings linking biofilm colonization with increased eDNA removal and degradation. Additionally, when biofilm was present, light availability increased eDNA removal; eDNA levels fell below detection after 6-18 h for open mesocosms versus 18-48 h for shaded mesocosms. Among size classes, larger particles (>10 µm) were removed faster than small particles (1.0-0.2 µm). These results suggest that changes in the distribution of eDNA size classes over time (e.g., with downstream transport) and with differing environmental conditions could be used to predict the location of target organisms in flowing waters, which will advance the use of eDNA as a tool for species monitoring and management.