As the spread of the new coronavirus continues, researchers at the University of Arizona Water and Energy Sustainable Technology Center are using municipal wastewater to monitor the incidence of the virus in communities across the United States.
Sewage surveillance can be used to determine if the virus is present in a community, even if individuals are asymptomatic, as well as ensure the effectiveness of a municipality's wastewater treatment process.
"Testing the wastewater gives you an idea of the number of cases within a community and if the numbers are increasing or decreasing," said Ian Pepper, director of the WEST Center and a BIO5 Institute member. "The approach can also be used to help determine if an intervention is working to reduce the transmission of the virus."
"We will be able to determine if the virus persists in the community even if there are no reported new cases," said Charles Gerba, a microbiologist and professor of environmental science in the College of Agriculture and Life Sciences. "To me, it's a key to tracing the spread of a virus."
Environmental microbiologists have used sewage monitoring programs to study pathogenic viruses for decades, most notably in public health efforts to globally eradicate the poliovirus.
Through the development of the polio vaccine and global vaccination programs, the transmission of the poliovirus has fallen dramatically in the last 26 years. However, three countries have ongoing transmission – Nigeria, Afghanistan and Pakistan.
To detect polio transmission in a community, epidemiologists typically rely on reported cases of acute flaccid paralysis; however, the severe condition only occurs in a fraction of infections. As individuals may be infected without displaying symptoms or paralysis, environmental surveillance programs have been used to pinpoint silent transmission of the poliovirus through viral shedding found in community wastewater.
With advanced laboratory capabilities and expertise in coronavirus research, the WEST Center is uniquely situated to conduct sewage surveillance for COVID-19. Co-located within the Pima County Wastewater Treatment Plant, the facility has extensive expertise in the detection of human pathogenic viruses in wastewater.
"We have tested for hepatitis A, enteroviruses and noroviruses. We have approximately 15 different viruses that we regularly test for in sewage and recycled waters for reuse applications," said Walter Betancourt, a microbiologist with expertise in environmental virology and assistant research professor in the Department of Environmental Science.
Named for the crown-like spikes on their surface, coronaviruses were first identified in the mid-1960s. Worldwide, seven different coronaviruses are known to infect people and cause illness. Four of the coronaviruses are quite common. Three others, including MERS-CoV, SARS-CoV, and SARS-CoV-2, emerged in more recent years and are examples of zoonotic viruses that once infected only animals but made the species jump to humans.
COVID-19 is a new disease, and there remains a great deal to learn regarding transmission, the severity of the illness it causes, and to what extent it may spread in the United States, according to the U.S. Centers for Disease Control and Prevention.
A 2008 study conducted by WEST Center researchers measured the survival of coronaviruses in wastewater. They found coronaviruses die off very rapidly in wastewater, with a 99.9% reduction in two to three days.
With their sewage surveillance program, researchers at the WEST Center will use molecular methods and nucleic acid targets recommended by the CDC to detect SARS-CoV-2 genetic markers in sewage samples collected prior to and following wastewater treatment.
As the new strain of coronavirus is investigated, the WEST Center hopes to correlate viral concentrations in sewage with recorded numbers of infections to help public health officials better prepare for the future.
Further investigations based on sewage surveillance and more recent next-generation sequencing approaches may help identify variants circulating in the population and assess the effectiveness of mitigation strategies to control and prevent the disease.