Scientists have detected traces of omicron in wastewater in Houston, Boulder, Colo., and two cities in Northern California.

It's a signal that indicates the coronavirus variant is present in those cities, and it highlights the useful data produced by wastewater surveillance research as omicron looms.

Gathering this data requires careful collaboration among wastewater facilities, engineers, epidemiologists and labs. Scientists and public health officials say the data derived from samples of feces can help fill in the gaps from other forms of surveillance and help them see the big picture of the coronavirus pandemic, especially as a new variant emerges.

In San Jose, Calif., it all starts in a tunnel under the San José-Santa Clara Regional Wastewater Facility, which processes sewage from about 1.4 million people and 22,000 businesses.