Researchers to track virus in Guam’s sewage systems
By Louella Losinio
The Centers for Disease Control and Prevention and other federal agencies have tapped into sewage surveillance technology to monitor and detect SARS-CoV-2, the virus that causes Covid-19, in public wastewater systems.
With the emergence of new Covid strains and the rising number of cases on the island, the Guam Department of Public Health and Social Services took advantage of the opportunity to participate in the nationwide program.
DPHSS partnered with the Guam Waterworks Authority for the program. At the 2021 Annual Water and Wastewater conference organized by the American Waterworks Association-Western Pacific subsection, representatives from both agencies provided an overview of the partnership.
According to the CDC, wastewater can be tested for RNA from SARS-CoV-2. Research showed that SARS-CoV-2 can be “shed in the feces of individuals with symptomatic or asymptomatic infection; so, wastewater surveillance can capture data on both types of infection.”
As part of the nationwide surveillance program, Guam will be receiving a PCR testing instrument and assay kit for testing samples from the island’s wastewater plants.
The equipment will be housed at the GWA laboratory, according to Paul Kemp, GWA assistant general manager for compliance and safety.
“We were already handling wastewater on a regular basis and knew how to deal with it in such a way that there is no risk to the staff who are managing the unit,” Kemp said, explaining the decision to put the equipment at the new GWA wastewater laboratory.
While waiting for the equipment to arrive, Public Health embarked on an initial data-gathering process in which wastewater samples from the Agana and Northern Wastewater Treatment Plants were collected, sent off-island, and analyzed using Biobot analytics technology.
“We had an opportunity given to us by a national grant to examine the levels in the wastewater at wastewater plants and since our equipment has not arrived, we took advantage of it,” Kemp said. “The data gives us an idea of what to expect when we get our own system up and running.”
Vince Campo, a public health research and statistical systems analyst, said the wastewater samples were compared with DPHSS Covid data. “Because we weren’t able to send these off every day and get a count every day, we only sent it about twice a week. From July to mid-August, we were able to get a more dynamic look at what the viral load looks like in our community.”
Guam is one of the state and territorial public health departments that received funding from the CDC for wastewater surveillance monitoring.
As part of the program, wastewater surveillance data from Guam and other communities will be collated in a national database. The objective is to use the data to evaluate the impact of Covid-19 on these communities and to develop public health measures in response to the pandemic.
The program is still in the pilot phase. “The idea is that we will have wastewater surveillance capabilities in the future once we get the machine set up,” Dr. Ann Pobutsky, territorial epidemiologist told participants at the virtual conference.
“This will be mainly for things that are shed in wastewater. But it is good for Covid because Covid is shed in feces. So, we are hoping that once this project gets going, we will have regular surveillance data not just for Covid but for other potential outbreaks for things like shigella.”
Researchers around the world are now pursuing the same approach for Covid-19 with the hope that wastewater data can supplement current measures of its prevalence. SARS-CoV-2 has already been detected in wastewater.
On Guam, Pobustky said the program is anticipated to take off before the end of the year. “We’ll see how this goes with the procurement process,” she added.
Wastewater surveillance for RNA from the virus that causes Covid-19 is a developing field, according to CDC. However, the technology has been used before for the early detection of other diseases such as polio.
“Sewage testing over time can provide trend data that can complement other surveillance data that inform public health decision-making. However, at this time, it is not possible to reliably and accurately predict the number of infected individuals in a community based on sewage testing,” CDC stated on its website.
CDC also listed several other current limitations of the system. Since the surveillance focuses on community or village-level wastewater systems, it will not be able to capture data from homes with septic-based systems or from facilities with decentralized systems.
Not all wastewater treatment plants are appropriate for site surveillance, CDC said, citing the need to understand the current limits of the testing capability.
“Low levels of infection in a community may not be captured by sewage surveillance. The lower limits of detection (i.e., the smallest number of people shedding the virus in their stool that can still be detected by current testing methods) for sewage surveillance are not yet well understood,” the CDC said. “More data on fecal shedding by infected individuals over the course of the disease are needed to better understand the limits of detection.”
At the virtual conference, participants also raised concerns over the safety of the personnel gathering and testing the samples at the treatment plant and laboratory.
CDC said there is no information to date that anyone has become sick with Covid-19 because of direct exposure to treated or untreated wastewater.
Kemp said protocols are set in place. “We have sampled and monitored wastewater on a regular basis and we have (standard operating procedures) for protecting our staff and the people who collect samples—the people who actually work in the wastewater plants.”
He said there are established procedures and protocols for handling wastewater that are maintained. “I am pretty confident in our safety history in waterworks and we seem to be doing it pretty well,” Kemp said.