Whole campus wastewater surveillance of SARS-CoV-2 for COVID-19 outbreak management.

In this long-term study (eight months), a wastewater-based epidemiology program was initiated as a decision support tool for the detection and containment of COVID-19 spread in the Technion campus. The on-campus students' accommodations (∼3,300 residents) were divided into housing clusters and monitored through wastewater SARS-CoV-2 surveillance in 10 manholes. Results were used to create a 'traffic-light' scheme allowing the Technion's COVID-19 task force to track COVID-19 spatiotemporal spread on the campus, and consequently, contain it before high morbidity levels develop. Of the 523 sewage samples analysed, 87.4% were negative for SARS-CoV-2 while 11.5% were positive, corroborating morbidity information the COVID-19 task force had. For 7.6% of the SARS-CoV-2 positive samples, the task force had no information about positive resident/s. In these events, new cases were identified after the relevant residents were clinically surge tested for COVID-19. Hence, in these instances, wastewater surveillance provided early warning helping to secure the health of the campus residents by minimising COVID-19 spread. The inflammation biomarker ferritin levels in SARS-CoV-2 positive sewage samples were significantly higher than in negative ones. This may indicate that in the future, ferritin (and other biomarkers) concentrations in wastewater could serve as indicators of infectious and inflammatory disease outbreaks.

Quantitative microbial risk assessment of Legionella pneumophila in a drinking water supply system in Israel.

Legionella pneumophila cause human infections via inhalation of contaminated water aerosols, resulting in severe pneumonia. Legionella spp. prevalence was monitored in a drinking-water distribution system (DWDS) in Northern Israel. Five points (toilet faucets and showers) were sampled seasonally along a three years period. Toilet faucets and shower use, both generating aerosols, are known transmission routes for this pathogen and thus, present a potential health risk. Quantitative Microbial Risk Assessment (QMRA) was applied in order to assess the health risks posed by Legionella for these two exposure scenarios, while considering Legionella seasonality. The obtained results were compared with estimated tolerable risk levels of infection and of disease set by the USEPA and WHO. Both limits were expressed as Disability-Adjusted Life Years index (DALY) being 1 × 10-4 and 1 × 10-6, respectively. The QMRA revealed that the annual risk levels for both faucets and showers use exceeded the acceptable risk of infection with an average of 5.52 × 10-4 and 2.37 × 10-3 DALY'S per person per year, respectively. Annual risk levels were stable with no significant differences between the three years. Risk levels varied significantly between seasons by up to three orders of magnitude. Risk levels were highest during summer, autumn, and lowest during winter. The highest seasonal infection risk values were found in summer for both faucets and showers, which corresponded to 8.09 × 10-4 and 2.75 × 10-3 DALY'S per person per year, respectively. In conclusion, during summer and autumn there is a significant increase of the infection risk associated with exposure to Legionella-contaminated aerosols, in the studied water system. Public health assessment and prevention measures should focus on these seasons.