Safety by degrees

The precautions needed when working on a pathogen are determined by the threat it poses.

Biosafety level (BSL) Typical precautions Examples
1: Agents not associated with consistently causing disease in healthy adults Lab coat and gloves Bacillus subtilis
2: Agents causing mild, treatable human disease Biosafety cabinets; limited lab access Rabies, polio, seasonal flu
3: Agents causing serious human disease with possible treatment: high individual risk, low community risk Decontamination of waste and lab clothing Tuberculosis, anthrax, SARS
3 ‘Enhanced’: Borderline BSL-3/BSL-4 Lab in isolation zone; dedicated power and air systems Reconstructed 1918 flu virus
4: Agents likely to cause serious human disease with no treatment: high individual risk, high community risk Full-body, air-supplied, positive pressure suits Ebola, Nipah virus
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