A bridge tournament in Colorado Springs in early March was responsible for a coronavirus outbreak that has killed four people, put 20 in the hospital, and infected scores more. But Colorado authorities say it would have been even worse if they had not quickly traced the first victim’s movements after her March 13 death, the Denver Post reports. The investigation found that the 80-year-old woman could have been in contact with 150 people—and then they learned one of those potential carriers attended choir practice with another 100 people. Making sure all those people quarantined helped contain the outbreak from spreading even further, officials said.