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Oahu this month became one of many communities across the world testing wastewater for the new coronavirus.

that the amount of the virus detected in a community’s sewage the rise and fall of infections, raising hopes for a cheap and reliable early warning tool. The virus that causes COVID-19 can be detected in a person’s fecal matter within three days of infection, much earlier than the 14 days it can take to develop symptoms.

“Sewage provides a statistical sample of the population,” said Rick Bennett, a microbiologist with a specialty in infectious diseases on the Big Island. “To get the same data with nasal swabs, you would need just an army of public health workers.”

Employees with the Honolulu Department of Environmental Services, who already regularly test wastewater, are taking nine samples a week, one from every public wastewater treatment plant on Oahu.

The samples are then sent to BioBot Analytics, a laboratory partnering with Massachusetts Institute of Technology, Harvard University and Brigham and Women’s Hospital. Before the pandemic, BioBot tested sewage to determine the levels of opioid use in a community.

“As we attempt to go back to normal it will be a very slow process largely because we will have to overcome people’s fear.” — Rick Bennett, microbiologist

Wastewater from 170 facilities in the country are being sent to the COVID-19 testing program.

“In an optimal world, they said we would have the results in three to four days,” said Josh Stanbro, Honolulu’s chief resilience officer and executive director of the Office of Climate Change, Sustainability and Resiliency. “But with so many other cities signing up, we’re seeing it more like nine days, maybe even more.”

Even if results take longer than a week, officials say wastewater testing provides more robust information about outbreaks since asymptomatic carriers, who are unlikely to receive a nasal swab test, are included.

The first samples were taken and frozen on May 1, before the deal with BioBot was even finalized. Stanbro wanted to have a snapshot of Oahu’s viral load during the strictest shelter-in-place order.

“The first stage of reopening was on April 30 … so we needed the data of what the virus levels were before opening so we have a baseline to compare as we open back up,” he said.

The results will be compared week-by-week and used in conjunction with results from nasal swabbing and antibody tests to paint a clearer picture of the virus’s spread on Oahu.

“We were looking at this as more tools in the toolbox,” said Department of Environmental Services deputy director Ross Tanimoto.

“As we attempt to go back to normal, it will be a very slow process largely because we will have to overcome people’s fear,” Bennett said. “If we can point to several weeks of sewage data and say ‘Hey there’s no detectible virus’ that would be pretty good.”

Funding for the $25,000 two-month pilot program came from a federal emergency aid package, and officials will decide whether to continue testing once they get a few weeks of results back.

Stanbro said the city is looking into opportunities with a local laboratory to speed up results and help the economy.

“We think it would be better, given the economic situation, to be creating lab jobs here rather than elsewhere,” he said.

There are no plans to collect more than nine samples a week or release the wastewater results by sub-region.

But Bennett hopes that as wastewater testing improves, officials will test sewage from every pipe entering the treatment plant to hone in on specific communities.

“For example if a small community, like Wahiawa, had a high amount, the public health officials could focus their nasal swabbing there and see why there’s more contagion going on there,” he said.

While most of Oahu is served by sewers, a similar program on other islands like Maui and the Big Island would be constrained by the higher proportion of cesspools and septic tanks.

Stanbro said officials on Kauai are considering it but so far no other counties have announced specific plans.

Beyond COVID-19

In 2011, sewage testing in Honolulu . Similar testing around the world has zeroed in on outbreaks of antibiotic-resistant bacteria, measles and .

But the tool isn’t only for emergencies. Japan regularly tests wastewater for all kinds of diseases, said Bennett.

“It’s been especially successful for norovirus, also known as cruise ship disease, in that country and it’s something that this island could implement for the health of people here,” he said.