Even after COVID-19 is cleared from the respiratory tract, the infection may stick around in the gut for days, a new study suggests. Hong Kong researchers examined stool samples from 15 patients and found some intriguing clues about how the virus operates inside the body. Almost half the patients had an active infection in their digestive tract—and it persisted for up to six days after negative respiratory swabs in some of them, Bloomberg reports. The findings show that fecal matter is a potential source of coronavirus spread and suggest that gastrointestinal treatments may be needed.