Testing for COVID-19 in SF wastewater – The San Francisco Examiner

When people think of the words “COVID-19” and “test,” the images that come to mind are usually long nasal swabs, worn by people wearing full personal protective equipment. Screening individuals has been the primary way to track the spread of the disease in San Francisco, but it’s not the only method available. Testing sewage – the natural waste that we throw down our toilets, as well as water from showers or sinks – is another tactic, which can often identify the spread of disease faster than careful testing on residents. from the city.

As of April, UC Berkeley has been studying sewage samples from 11 Bay Area districts, including San Francisco. It is a project that is gaining speed; While 30 samples per week can be tested currently, the team plans to increase that number to 200 samples per week by the end of the year.

In San Francisco, samples are collected from wastewater treatment plants, several neighborhoods, and a residential care facility. Data detected by UC Berkeley could be vital for local health departments to keep up with a sudden increase in the spread.

“From the very start of the pandemic, it was clear that there were major limits to the ability to test every individual in a population frequently enough to know whether or not they were infected,” says Kara Nelson, professor of engineering. civil and environmental. at UC Berkeley. “Wastewater naturally aggregates the waste of hundreds, if not millions of people into a single sample, so if you can collect a representative sample of wastewater and analyze it, you can get a tremendous amount of information that you can’t probably could not get by testing people. individually.”

But determining traces of COVID-19 is tricky: detecting the virus in wastewater samples is decidedly more difficult than finding a nasal swab there. On the one hand, wastewater contains more than just wastewater. Bleach is added as a disinfectant and to control odors, which can break down and kill the COVID-19 virus as it travels through sewers.

“The research community has yet to find evidence of the survival of the COVID-19 virus in wastewater systems,” said Will Reismann, spokesperson for the San Francisco Public Utilities Commission. “Essentially, the virus dies, but remnants of RNA (the copies of the gene) remain in the sewage samples.”

Wastewater also contains many other viruses, which makes it more difficult to isolate COVID-19 molecules from samples. Additionally, people excrete different amounts of COVID-19 particles in their poop, which can complicate studies of the prevalence of the virus in certain areas.

UC Berkeley has found workarounds for the above issues. The answer lies in something we all have at home: table salt. Nelson’s team teamed up with UC Berkeley’s Department of Molecular and Cellular Biology and found that salt can open up the virus’s outer layer, causing it to dump all of its genetic material into a single, collectable sample. . Salt has the added benefit of capturing pieces of virus particles that can be partially disintegrated and keeping them for testing.

It turned out to be a very effective system. Not only is it fast (results can be determined in eight hours), it is also very sensitive. It is possible to detect whether a small number of people excrete the virus in a sample of sewage containing material from thousands of people.

This isn’t the first time that San Francisco shit has been investigated.

“The SFPUC constantly tests our wastewater to ensure public health for chemical and biological parameters,” says Reismann. “We regularly collaborate with the research community to help advance the science of wastewater treatment.

But this is the first time that the stakes can be so high. Ultimately, this model could be used to test specific areas – like a nursing home or a neighborhood where the number of individual tests is low – to detect an outbreak early.

“One of the huge bottlenecks in wastewater testing comes from capacity testing,” Nelson says. “This pop-up lab is the first high-throughput lab in the Bay Area that has the capacity to bring in large numbers of samples and quickly deliver results to public health officials.”

UC Berkeley provided the data from its study to the San Francisco Department of Public Health, but so far the city has neither used it nor made it public.

“Although wastewater testing is not currently part of our infectious disease surveillance, it could be in the future,” the ministry said. “We look forward to working with researchers and other city agencies to determine how best to collect and use this data.”

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News from the Coronavirussan Bay region