Berkeley is analyzing sewage data to track COVID-19 as response shifts in third year of pandemic

As self-testing becomes more common, the Berkeley health officer said the data is a useful tool in monitoring COVID-19 in the general population.

BinaxNOW COVID-19 Tests
In the current stage of the pandemic, many Berkeley residents are using self-tests, like the BinaxNOW COVID-19 tests, to monitor whether they have the virus. Before, residents relied on testing sites that reported data to the local health department. Credit: Amir Aziz

When the Grand Princess cruise ship docked in Oakland in March 2020 and the entire country began scrambling for information on the new virus at its shore, a local sewage agency activated a tool that has become key in responding to this pandemic — and future ones.

East Bay Municipal Utilities District manages sewage lines that run through Berkeley, Oakland and the East Bay, roughly bounded by Hayward, Crockett and San Ramon, and processes an average of 50 million gallons of water daily.

The agency has always tested and treated this supply to meet state and federal standards, but it began navigating unknown territory when the ship with COVID-19 patients arrived in the Bay Area and asked EBMUD to take its wastewater.

Working with the Centers for Disease Control and Prevention, state public health agencies and scientists at Stanford and UC Berkeley, EBMUD found they could check the water for COVID-19 and ultimately assess it for new variants, like delta, omicron and BA.2.

“People who swim in the Bay were also concerned about getting COVID,” said Alicia Chakrabarti, EBMUD manager of wastewater management, describing the haze of confusion around COVID-19 in the early months of the pandemic. The agency was able to determine that the waters were safe, both for workers in their plants and people who access the waters recreationally.

In April, the state department of public health started processing the samples locally instead of at UC Berkeley. That data is available on their online dashboard.

Data from the “Cal-SuWers” dashboard aligns with COVID-19 trends shown in testing from 2020 to 2022. The blue line shows a rolling average of all COVID-19 samples in the wastewater, and each point shows the average for that day. Credit: California Department of Public Health, April 29, 2022.

Berkeley has its own health department and began using the EBMUD data in the fall of 2020. It was the first time the city ever accessed sewage data for its public health strategy, according to Health Officer Dr. Lisa Hernandez. 

In the months since, officials have used the numbers to track the presence of the virus in the community as a supplement to diagnostic tests (like those from testing sites). Sewage typically detects case jumps about a week before testing, and eventually hospitalizations, reflect the same.

This predictive tool helps the city determine when they need to do more education and outreach about COVID-19, Hernandez said.

“We’re able to capture a broader part of our community with wastewater testing because we know that not everyone that needs to get tested, doesn’t always want to, or can, get tested,” Hernandez said.

Because the sewage lines are interconnected throughout the East Bay, the data is purely population-level — meaning officials can’t track individual homes or blocks — but it can be specified as “catchment areas,” which can split up the city into regions, Hernandez said.

The numbers from sewage data have matched up to — and in some cases, preceded — county data from diagnostic tests. For example, EBMUD Director of Wastewater Eileen White said the numbers from different pipes showed COVID-19 numbers being higher in Oakland than Berkeley throughout the pandemic, due to a range of socioeconomic and health factors.

Other regions, like Santa Clara County, also used this wastewater data to predict the presence of the omicron variant in their cities. Hernandez said Berkeley actually found out about the omicron variant from traditional channels due to a large outbreak at Kaiser’s Oakland Medical Center in December 2021, but it is a useful tool to monitor for other variants and spikes in cases.

What is the future of wastewater data in Berkeley?

A new graph on the city’s COVID-19 tracker compares case rates by month between the three years of the pandemic.

Berkeley is currently experiencing a small spike in cases, which Hernandez attributed to spring break travel and the more contagious variant, BA.2. Berkeley Unified School District reported a “significant uptick” in cases on Thursday, saying its schools saw 91 cases this week — more than three times as many as the previous week.

Though the current average case rate (about 38 daily) citywide is much lower than the numbers observed at the height of the omicron surge this winter, Hernandez emphasized that these numbers are higher than they were this month in 2021 and 2020.

Testing has fallen considerably from levels during the omicron surge, when lines once again wrapped around testing sites, and appointments were difficult to come by. Because residents have the additional tool of self-tests to monitor COVID-19 infections, Hernandez said it’s about 50-50 whether cases are caught by an official diagnostic test (which is reported to the city health department) or a self-test.

That can lead to less data for the city, but Hernandez said the self-tests are still “more of a blessing than a curse, because people can rapidly get information about whether they have COVID or not and hopefully do the right thing.”

Funding for testing sites is also falling, and while city testing and vaccine sites are still free without insurance, others like Curative have started charging for certain options — like the fastest rapid test. Testing sites may become less available as the government reallocates funding into other priorities, and Hernandez said this could be a time when population-wide data through wastewater becomes even more important.

“I think wastewater sampling is going to be a definite, strong tool in our surveillance toolbox,” Hernandez said.

Hernandez and officials at EBMUD also hope it can be adapted to test for things like the common flu, or respiratory syncytial virus, a common respiratory virus. White and Chakrabarti said these processes are still in the initial stages, and private labs have expressed interest in analyzing the wastewater to spot other bacteria and viruses.

EBMUD was not designed to take samples for COVID-19 or other viruses, and the process has been a huge lift for the agency, especially when its workers (half of whom work at plants and cannot be remote) were coming down with the virus during the worst parts of the surge, White said.

She added that Gov. Gavin Newsom’s pandemic plan includes wastewater surveillance, and utility agencies that do similar work are hoping for additional support on the local and federal levels.

“It’s a very time-consuming effort, but it’s the right thing to do,” White said. “We’ve always treated wastewater to protect public health, and now we’re looking for opportunities on how we can take wastewater and turn it into a resource.”

Supriya Yelimeli is Berkeleyside's homelessness and housing reporter. Email: supriya@berkeleyside.org. Twitter: SupriyaYelimeli. Phone: 510-585-8315.