Publications by Timothy R. Julian

Estimated transmission dynamics of SARS-CoV-2 variants from wastewater are unbiased and robust to differential shedding

The COVID-19 pandemic has accelerated the development and adoption of wastewater-based epidemiology. Wastewater samples can provide genomic information for detecting and assessing the spread of SARS-CoV-2 variants in communities and for estimating importan ...

2025

Transmission dynamics of Norovirus GII and Enterovirus in Switzerland during the COVID-19 pandemic (2021-2022) as evidenced in wastewater

Tamar Kohn, Htet Kyi Wynn, Shotaro Torii, Timothy R. Julian

Noroviruses and enteroviruses are major causes of endemic gastrointestinal disease associated with substantial disease burden. However, viral gastroenteritis is often diagnosed based on symptoms, with etiology infrequently tested or reported, so little inf ...

Elsevier BV2025

Monitoring an Emergent Pathogen at Low Incidence in Wastewater Using qPCR: Mpox in Switzerland

Tamar Kohn, Timothy R. Julian

Wastewater-based epidemiology offers a complementary approach to clinical case-based surveillance of emergent diseases and can help identify regions with infected people to prioritize clinical surveillance strategies. However, tracking emergent diseases in ...

2024

Waterborne virus transport and the associated risks in a large lake

Tamar Kohn, Xavier Fernandez Cassi, Chaojie Li, Timothy R. Julian

Waterborne enteric viruses in lakes, especially at recreational water sites, may have a negative impact on human health. However, their fate and transport in lakes are poorly understood. In this study, we propose a coupled water quality and quantitative mi ...

2022

Inferring Transmission Fitness Advantage of SARS-CoV-2 Variants of Concern in Wastewater Using Digital PCR

Tamar Kohn, Xavier Fernandez Cassi, Timothy R. Julian

Throughout the global COVID-19 pandemic, SARS-CoV-2 genetic variants of concern (VOCs) have repeatedly and independently arisen. VOCs are characterized by increased transmissibility, increased virulence, or reduced neutralization by antibodies obtained fro ...

2022

Early detection and surveillance of SARS-CoV-2 genomic variants in wastewater using COJAC

Tamar Kohn, Xavier Fernandez Cassi, Federica Cariti, Alex Tunas Corzon, Timothy R. Julian, Carola Bänziger

The continuing emergence of SARS-CoV-2 variants of concern and variants of interest emphasizes the need for early detection and epidemiological surveillance of novel variants. We used genomic sequencing of 122 wastewater samples from three locations in Swi ...

2022

Wastewater monitoring outperforms case numbers as a tool to track COVID-19 incidence dynamics when test positivity rates are high

Tamar Kohn, Xavier Fernandez Cassi, Joseph Chadi Benoit Lemaitre, Federica Cariti, Alex Tunas Corzon, Timothy R. Julian, Carola Bänziger

Wastewater-based epidemiology (WBE) has been shown to coincide with, or anticipate, confirmed COVID-19 case numbers. During periods with high test positivity rates, however, case numbers may be underreported, whereas wastewater does not suffer from this li ...

2021

Adaptation of Human Enterovirus to Warm Environments Leads to Resistance against Chlorine Disinfection

Tamar Kohn, Anna Carratala Ripolles, Virginie Bachmann, Timothy R. Julian

Sunlight, temperature, and microbial grazing are among the environmental factors promoting the inactivation of viral pathogens in surface waters. Globally, these factors vary across time and space. The persistence of viral pathogens, and ultimately their e ...

2020

Retention of E. coli and water on the skin after liquid contact

Tamar Kohn, Timothy R. Julian

The frequent contact people have with liquids containing pathogenic microorganisms provides opportunities for disease transmission. In this work, we quantified the transfer of bacteria—using E. coli as a model- from liquid to skin, estimated liquid retenti ...

2020

Safely Managed Hygiene: A Risk-Based Assessment of Handwashing Water Quality

Matthew Eric Verbyla, Timothy R. Julian

Sustainable Development Goal (SDG) Indicator 6.2.1 requires household handwashing facilities to have soap and water, but there are no guidelines for handwashing water quality. In contrast, drinking water quality guidelines are defined: water must be "free ...

2019