An explosion of coronavirus infections at California's San Quentin State Prison, the state's oldest, has public health officials there worried about its impact on prisoners, staff and the wider hospital system in the San Francisco Bay Area. "Shocking, heartbreaking are certainly the words I would use to describe it," said David Sears, a physician and professor of medicine at the University of California, San Francisco. He recently toured San Quentin and warned officials about just such an outbreak. "It's devastating how fast this has moved through the prison," he said. There were no inmate coronavirus cases at the prison throughout March, April and May. Today, there are more than 600 infections. And the numbers are rising fast. Public health officials and prison advocates say the outbreak was entirely preventable. They point to a transfer in late May of 122 inmates to San Quentin from an overcrowded state men's prison in Chino, where COVID-19 is ravaging the inmate population. "Unfortunately, they arrived untested and were placed within San Quentin and really kind of seeded an outbreak in a second state facility," said Dr. Matt Willis, public health officer for Marin County, where San Quentin is located. "In the rush of trying to address that epidemic at Chino, that [testing] step may have been overlooked."