Wild polioviruses are classified as risk group 2. The rationale for the minimal biosafety levels is the near universal immunization of the population with OPV and/or IPV.
Biosafety Level 2 (BSL-2) is the currently recommended minimal standard for all countries. To ensure safe handling of wild polioviruses and potentially infectious materials as eradication nears (Pre-Eradication), BSL-2, hereafter referred to as BSL-2/polio, should be enhanced by specific practices described in this document
(Box 10).
Comments
I can tell you've never seen a level 3+ lab.
Polio requires level 4.
http://www.biosafety.be/Polio/GlobalActionPlanWHO.pdf
Your link directly contradicts you.