The GAO has issued a report entitled “Biosafety Laboratories: Perimeter Security Assessment of the Nation's Five BSL-4 Laboratories.”. For this report, the GAO conducted a physical security assessment of the nation’s five biosafety level (BSL) 4 labs, which handle the world’s most dangerous agents and diseases. Based on findings of inconsistent levels of protection against unauthorized intrusions, the GAO recommends that the Director of the Centers for Disease Control and Prevention (CDC) adopt specific perimeter control requirements for all BSL-4 labs. HHS indicated that further study is required prior to additional regulation.