WordNet records no synonym and no antonym for biosafety level 4. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
exposure to exotic infectious agents that pose a high risk of life-threatening disease and can be transmitted as an aerosol and for which there is no vaccine or therapy
Synonyms, antonyms and the broader and narrower relations for biosafety level 4 come from Princeton University’s WordNet. Full sources and licences.