As COVID-19 recedes into the background, there are nagging doubts: Is the pandemic really, truly over? Are there other variants out there preparing to strike?

It’s hard to know. The days of mass testing and daily data reports have passed. Thanks to vaccinations and less-virulent versions of COVID, symptoms often are so mild that they go unreported or undetected.

That’s why health officials here and nationally are advancing a proven early-warning system: wastewater testing. The process involves taking samples of untreated sewage and analyzing it in labs to see what it contains — specifically, for the presence of SARS-CoV-2, the virus that causes COVID-19.

Wastewater testing has certain advantages for disease surveillance. It doesn’t require testing individuals; it’s broad-based and anonymous; it can detect viruses before they appear in the general population. Public health officials can track rising cases of a particular disease and respond before the infection becomes widespread.

However, the science isn’t straightforward. Wastewater contains many biological and chemical targets that could make it more difficult to extract specific, useful data. Also, it may be harder to determine if an infectious disease is spreading in the local community; Hawaii’s large population of tourists, who go everywhere, could skew the data.

To make the most of wastewater surveillance, experts say the information should be analyzed with other data, including historical and geographical contexts where the wastewater is gathered, and actual clinical cases of infection.

All this means Hawaii should not only move ahead with expanding wastewater testing — which it is — but make it a permanent feature of health policy that keeps up with improving technology.

As part of its new National Wastewater Surveillance System, started in 2020, the Centers for Disease Control and Prevention (CDC) has tapped into 15 Hawaii sewer sites statewide, reporting its results online. The state Department of Health is preparing to set up its own testing system here, to reduce the time waiting for results. And the University of Hawaii, partnering with the city, built on a National Science Foundation grant to study how the coronavirus mutates.

That’s all for the good. It’s important, though, that Hawaii’s scientists, researchers and public health officials not work in silos. They should collaborate when necessary to extract the maximum benefit to public health that wastewater testing can provide.