Boise’s wastewater could be an early warning sign of COVID-19 infections

BOISE – There might be another way to tell if an outbreak of COVID-19 is coming to Idaho: Boise’s wastewater.

Since May, the city of Boise has been sampling wastewater at water renewal facilities to test for the presence of COVID-19 in fecal matter. Although this does not tell the city exactly how many people are infected, increased levels of the disease could be an indicator of rising cases.

The sampling began after Boise was approached by wastewater epidemiology company Biobot, based in Somerville, Massachusetts, if the city was interested in participating in its new program to have its wastewater tested for the presence of the disease. The goal was to add more data about community spread in the hopes it could aid in decision-making, especially in the early weeks of the pandemic in the United States when less was known about the disease.

“You don’t have to be a public health expert to know the data we have around COVID-19 is imperfect,” Boise’s enterprise data strategist Kyle Patterson said. “Very few people actually get tested, and if you’re asymptomatic you’re likely not getting tested, but everybody uses the bathroom, so we’re getting an idea of how the virus is spreading that way.”

The results of daily samples are available on a dashboard on the city of Boise’s website. It has a trend line showing the prevalence of COVID-19 in the samples over time compared to a graph of confirmed cases in Ada County. As of Aug. 3, the system was reading 2.7 million virus copies per liter, which is up from the July 28 number of roughly 875,000 virus copies.

Virus copies per liter is the quantity of a virus in any given volume of fluid.

That statistic may not seem significant on its own, but Boise’s environmental manager Haley Falconer said being able to see the levels go up or down over time could help the city predict the trajectory of infection levels. It is still unknown if the virus’s level in fecal matter is a “leading indicator,” or an early warning sign, of increasing infection levels before traditional tests come back, but Falconer said there is “promising” evidence suggesting it is.

“By no means is this the only piece of information, and the city knows this needs to be used in combination with other data and the single data points isn’t necessarily what is the most important thing,” she said.

Technology and research on COVID-19 in wastewater is limited, but it has been proven to be an early way to detect the virus before residents test positive. In the Netherlands, scientists detected SARS-CoV-2, the virus that causes COVID-19, in fecal matter days before the first patient tested positive for the disease in 2019.

Boise was part of Biobot’s original program for testing wastewater in 400 public utility systems in 42 states for COVID-19. For the first month, it cost the city $120 per sample to collect the material and ship it to Biobot for testing, but in June the price increased to $1,200 per sample and the city changed labs to work with the University of Missouri. The new tests cost $175 per kit, which is paid out of the city’s water renewal enterprise fund.

City officials do not know why Biobot increased its prices. The city spent $19,680 on testing through Biobot, but has not yet received an invoice from the University of Missouri to calculate the total spent on the program.

The city of Boise collects the data and sends it to Central District Health, which is in charge of making public health policy decisions. Brandon Atkins, a spokesman for the health district, said the data is helpful information to show when numbers might soon spike, or if there are large numbers of asymptomatic individuals, but as of now it is not a major part of how the district makes decisions.

“This information could be a helpful indicator or levels of COVID within the community prior to seeing the numbers increase in testing and/or hospitalizations,” Atkins said. “However, because the data is fairly new and not easily tracked to specific locations within the community, it is mostly informational only.”