List of organisms that require handling with the most severe protocol
Biosafety level 4 (BSL-4) organisms are dangerous or exotic agents which pose high risk of life-threatening disease, aerosol-transmitted lab infections, or related agents with unknown risk of transmission.[citation needed]
Not all select agents require BSL-4 handling, namely select bacteria and toxins, but most select agent viruses do (with the notable exception of SARS-CoV-1 which can be handled in BSL3). Many non-select agent viruses are often handled in BSL-4 according to facility SOPs or when dealing with new viruses closely related to viruses that require BSL-4. For instance, Andes orthohantavirus and MERS-CoV are both non-select agents that are often handled in BSL-4 because they cause severe and fatal disease in humans. Newly characterized viruses closely related to select agents and/or BSL-4 viruses (for example newly discovered henipavirusesorebolaviruses) are typically handled in BSL-4 even if they aren't yet known to be readily transmissible or cause severe disease.[citation needed]
Globally, there are no official agreements on what agents must be handled in BSL-4. However, select agents and toxins originating or ending in US BSL-4 labs must adhere to US select agent laws.[citation needed]
