BSL-3 labs are facilities where work is typically performed on microbes that are indigenous or exotic, may contaminate the environment and can cause serious to potentially lethal diseases through exposure or inhalation (source: https://www.ltshealth.com/bsl-3). These labs have to be registered with the appropriate government agencies and are strictly controlled. Personnel are also under medical surveillance and have to adhere to rigorous safety rules. Agents that cause the West Nile fever and tuberculosis are examples of microbes that would have to be tested in BSL-3 labs (source: https://consteril.com/biosafety-levels-difference/).