BSL4 Facilities in Anti-Infectious Disease Measures
National Institute of Infectious Diseases, 1-23 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
Pathogens are divided into biosafety levels (BSL) 1 to 4 based on multiple factors such as virulence, transmissibility, environment effect, and treatment availability. BSL1 pathogens are the least virulent and BSL4 the most. BSL4 pathogens include ebolavirus, marburgvirus, Crimean-Congo hemorrhagic fever virus, lassa virus, variolla virus, and South American hemorrhagic fever viruses, as detailed in Table 1. Pathogens at each of the 4 BSLs must be handled in equivalently physically contained laboratories, graded P1-4. BSL4 pathogens do not exist in nature in Japan, which currently has no equivalent physical containment facilities, but the possibility exists that they may be brought into the country unintentionally by those infected in endemic areas or intentionally by bioterrorists.