How many biosafety level 4 labs are there?

As of recent reports, there are approximately 59 Biosafety Level 4 (BSL-4) laboratories worldwide, either operational, under construction, or planned. These facilities are designed for research on high-risk pathogens that can cause severe or fatal diseases in humans, for which no vaccines or treatments are available. The number of BSL-4 labs has been increasing, particularly in response to emerging infectious diseases and bioterrorism threats.