The CDC’s Select Agents and Toxins program requires that “theft, loss, release causing an occupational exposure, or release outside of primary biocontainment barriers” of agents on its watchlist be immediately reported. Between 2005 and 2012, the agency got 1,059 release reports — an average of an incident every few days.

Severe acute respiratory syndrome, or SARS, had an outbreak in 2003. Since then it hasn’t reoccurred in the wild, but there have been six separate incidents of it escaping the lab: one in Singapore, one in Taiwan, and four times at one lab in Beijing.