How scientists use wastewater to track the spread of COVID

As the newest dominant COVID subvariants BQ.1 and BQ.1.1 emerge, scientists are looking beyond traditional methods to track its spread. One important tool in their arsenal is wastewater surveillance. Special correspondent Cat Wise reports from California, one of the first states to test wastewater for COVID.

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  • John Yang:

    As the new dominant COVID variant called BQ1 emerges, scientists are looking beyond traditional methods to track its spread. The newest tool in their arsenal, wastewater.

    Special correspondent Cat Wise traveled to California, one of the first states to test wastewater for COVID.

  • Cat Wise, PBS Correspondent:

    Every day more than 100 million gallons of wastewater flows into this treatment facility in Santa Clara County, California. It`s the largest in the San Francisco Bay area, serving more than 1 million residents in Silicon Valley.

    The sewage spewing out from these tanks is something most people want to avoid.

    Alexandria Boehm, Environmental and Civil Engineering Professor, Stanford University: Extract the RNA from the wastewater.

  • Cat Wise:

    By Stanford University Environmental and Civil Engineering Professor Alexandria Boehm sees a public health goldmine.

  • Alexandria Boehm:

    Can we look at all the samples –

  • Cat Wise:

    Samples?

  • Alexandria Boehm:

    — together.

  • Cat Wise:

    In March of 2020, just weeks after one of the first coronavirus cases in the country was confirmed here in Santa Clara County, Boehm and her colleagues began testing wastewater samples.

  • Alexandria Boehm:

    We found that we could detect SARS-CoV-2 RNA in wastewater, and then we found that we could measure its concentration and see how it could change overtime and how that matched with data from reported cases.

    I was running with my cell phone, and I got in the first set of results, and I could see right then and there that the changes in concentration were similar to what was happening with the cases. And I was like, oh my gosh, I can`t believe this is going to work.

  • Cat Wise:

    Using wastewater to monitor viruses is not new. For decades scientists around the world have used wastewater to track polio outbreaks. But it had never been used to track a respiratory disease. People infected with COVID can shed their virus in their waste days or weeks before they may have symptoms, which Boehm says can provide an early warning for public health officials.

  • Alexandria Boehm:

    Wastewater surveillance is just – it could be like a complete revolution in the way that we track infectious disease in communities. And the uptake of this, like, technology is really unprecedented. We`ve gone from zero to 100 in like two years.

  • Cat Wise:

    In November of 2020, she and her colleagues launched a program to track COVID at eight northern California treatment plants. It has now expanded to 70 sites and is part of the CDC`s own wastewater surveillance system, which generates data from more than 1,000 sites.

  • Justin Sablaw, San Jose-Santa Clara Wastewater Facility Operator:

    Make sure everything runs smoothly.

  • Cat Wise:

    At the Santa Jose-Santa Clara Wastewater Facility, operator Justin Sablaw took us to an underground area where he and his colleagues take samples of semisolid waste, known as sludge, every four hours.

  • Justin Sablaw:

    Well we usually try to get 250 milliliters a sample roughly.

  • Cat Wise:

    The samples are sent to a lab where they`re tested not only for COVID but also influenza, Respiratory Syncytial Virus or RSV, and monkeypox, known mpox in California. The results are sent to public health officials around the country, including Dr. Sara Cody, the Head of Santa Clara`s Public Health Department.

    Dr. Sara Cody, Head of Santa Clara Public Health Department: What you really need to do is look at where are we now in the wastewater.

  • Cat Wise:

    Cody now has more than two years worth of data showing how closely COVID cases in her country correlated with virus levels in the wastewater. Then this summer Cody says fewer people were tested at clinics and hospitals, but wastewater concentrations stayed high.

  • Dr. Sara Cody:

    When I see this, I see why over time we`ve had growing confidence that the wastewater is the truth, and now we can certainly see that the wastewater levels are still elevated and we trust that. We know the wastewater doesn`t lie.

  • Cat Wise:

    Cody says she now regularly relies on Stanford`s data to make public health decisions, like recommending that residents continue to mask indoors in public places. One downside to wastewater monitoring, however, is time and money, but officials here say it only cost about $100 every time a disease is tested. That can vary elsewhere depending on location and population being tested.

  • Alexandria Boehm:

    If you take one sample of wastewater, you could get information about in San Jose about 1.5 million or even at a small plant 10,000 people. Multiply the cost of the wastewater test by the number of people, so in that sense wastewater is not cost prohibitive. It is actually really cheap and economical.

  • Cat Wise:

    Still there are concerns some communities will be left out as wastewater testing expands. The rural town of Esparto, where nearly 50 percent of residents are Latino, is now part of a program sampling treatment facilities across California`s Central Valley. Like many communities in the area, it was hit hard by the pandemic but didn`t have access to wastewater testing early on to track the spread.

    Heather Bischel, Civil and Environmental Engineer, UC Davis: This is something that becomes really important if we have wastewater monitoring data to make that available for the public.

  • Cat Wise:

    Heather Bischel is a Civil and Environmental Engineer at UC Davis and one of the lead researchers in the program. She says it`s important wastewater testing captures data for underserved communities.

  • Heather Bischel:

    What we wanted to do was help fill that data gap and really try to focus on increasing health equity by increasing access to data across all of our communities, and especially rural areas, agricultural areas, and disadvantaged communities.

  • Dr. Aimee Sisson, Yolo County Public Health Officer:

    Downgrade to our medium levels.

  • Cat Wise:

    Dr. Aimee Sisson is Yolo County`s Public Health Officer. She says wastewater surveillance can be especially helpful for tracking disease in communities that may have limited access to testing.

  • Dr. Aimee Sisson:

    Now we have this addition tool in our toolbox to be able to look at what`s happening in an entire community instead of relying on the people who are able to get tested, but I can`t make any individual-level decisions. I can`t say, you know, it was this household, this household, that household. And so, that`s the piece that we can`t tease out in terms of who needs to get treatment, who needs to isolate.

  • Cat Wise:

    Back at Stanford, Boehm hopes wastewater testing will continue to expand around the country.

  • Alexandria Boehm:

    I know in California that wastewater surveillance is probably here to stay, and I hope that there is enough funding through the state government and through the federal government to really make this part of our infrastructure for health monitoring in the United States.

  • Cat Wise:

    Infrastructure, she says, that could one day help prepare us for the next pandemic. For PBS News Weekend, I`m Cat Wise in San Jose, California.

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