The Houston Health Department has made an alarming discovery in the city’s sewage system. According to the NBC News affiliate KPRC-TV, wastewater samples collected in Houston last month have shown that the coronavirus variant first discovered in the United Kingdom is spreading fast. The variant was reportedly found at 31 of the city’s 39 wastewater treatment plants on Feb. 22—two weeks before that, it was only found at 21 of the plants. The discovery was announced a week after Texas Gov. Greg Abbott said he planned to end the state’s mask mandate and push all businesses to fully reopen. “The prevalence of the U.K. variant in our wastewater shows it’s actively spreading in our city,” said David Persse, chief medical officer for the city of Houston. “This is another clear indication that we must continue to mask up, practice social distancing, wash our hands, get tested and, get vaccinated when possible.”