Since the global emergence of SARS-CoV-2, the virus that causes COVID-19, wastewater surveillance of the infectious disease has enabled engineers and public health authorities in Houston, TX to detect and track the spread of infections in communities.
Although wastewater surveillance as a tool is not new, the gathering, organization and reporting of large amounts of data related to a disease-based ecosystem is, and it played a central role in Houston’s pandemic management.
“Houston is the fourth largest city in the U.S. with a very diverse population of about 2.3 million citizens. Sampling wastewater has served as a passive method of detection that does not require any action from the public,” said Loren Hopkins, the chief environmental science officer for the Houston Health Department and a professor in the practice of statistics at Rice University.
“The ability to monitor viral loads shed by humans at zip code and manhole levels has allowed public health authorities to use that information to guide interventions,” Hopkins said.
A commentary, published on July 28 in the journal Public Health Reports, co-authored by Hopkins and Stephen Williams, director of the Houston Health Department, details the department’s extensive collaboration with Rice University, Houston Public Works, and city and public health authorities to establish a wastewater surveillance program during the COVID-19 pandemic.
Houston’s city-wide surveillance and reporting system is organized into three parts, wastewater sampling and laboratory methods, statistical analysis and reporting, and targeted interventions and resources.
Laboratory methods to target pathogens have been led by Rice’s Lauren Stadler, an assistant professor of civil and environmental engineering. Statistical analysis and reporting efforts have been led by Katherine Ensor, Rice’s Noah G. Harding Professor of Statistics. Public health interventions and resources have been led by Hopkins and orchestrated by Williams and Dr. David Persse, the public health authority for the City of Houston.
The integrative analysis system has shown wastewater data on SARS-CoV-2 viral loads strongly correlates with trends from multiple disease indicators, such as COVID-19 positivity rate, emergency department visit rate, and hospital bed usage rate.
“We have learned many lessons since the COVID-19 pandemic began. Infection dynamics and hospital admissions have changed from variant to variant, and as people were vaccinated or acquired immunity, the wastewater monitoring and reporting system has served as a type of radar,” said Williams.
Williams said, “The system, which includes an interactive dashboard website combines with additional city-wide reporting measures to put us in an active rather than a reactive position.”
The analysis system integrates information from other Houston Health Department surveillance systems such as clinical positivity, hospitalization, vaccination rates, and pertinent Houston demographic data. Weekly COVID-19 viral load and infection rate summary reports have been shared with the mayor’s office, media outlets, various health authorities, schools and the general public.
The information was also used to guide public health interventions such as site visits, telephone calls, emails, materials distribution, COVID-19 education on testing and vaccination, workshops, and public health education classes.
In moving forward, Houston Wastewater Epidemiology collaborators have adapted wastewater surveillance and reporting to provide public health information on seasonal influenza and the respiratory syncytial virus, known as RSV.
Stadler says new environmental research at Rice is also being conducted to, “Enhance surveillance by investigating sensitive, sequencing-based methods into the framework that identify and analyze the presence of a range of microbes that are causative to human disease.”
The journal Public Health Reports is the official journal of the Office of the U.S. Surgeon General and the U.S. Public Health Service. Additional contributors to Houston’s wastewater surveillance paper include David Persse, MD, City of Houston public health authority and physician director of Emergency Medical Services, and professor of medicine and surgery for Baylor College of Medicine; Edward J. Septimus, MD, Department of Population Medicine, Harvard University; James J. McCarthy, MD, MH, Memorial Hermann Health System; Catherine D. Johnson, JD, Houston Health Foundation, Texas Children’s Hospital; Rebecca Schneider and Kaavya Domakonda of the Houston Health Department.
Shawn Hutchins, Communications Specialist