California-based engineer and scientist Patrick Vaughan made a troubling discovery July 10. Dozens of facilities providing COVID-19 wastewater data went offline, seemingly overnight.

Vaughan had been following WastewaterSCAN, a national program that monitors wastewater for diseases. He noticed that 42 of the previously reporting 194 facilities suddenly displayed small blue triangles with the message “data is no longer collected from this site.” The development came just as people across the U.S. scrambled for information during a summer COVID wave that even infected President Joe Biden.

“This is a major blow to our COVID wastewater tracking abilities,” Vaughan told his followers in a video he posted the same day.

Wastewater, which comes from processes such as laundry or toilet flushing, has emerged as a key indicator for the prevalence of COVID-19 in the general population since testing rates plummeted in 2022. State and federal governments have also unraveled many of the other metrics used to track the virus. For example, as of May 1, U.S. hospitals are no longer required to report key COVID data to the government. Several states have also stopped tracking COVID-19 infection rates altogether.