Biological agents are classified into:
Risk group 1: low individual risk for the worker and the community, with a low probability of causing disease in humans.
Risk group 2: moderate individual risk for the worker with a low probability of spreading to the community. They can cause diseases in humans for which effective prophylaxis or treatment exists.
Risk group 3: high individual risk for the worker with a probability of spreading to the community. They can cause serious diseases and infections in humans, for which effective prophylaxis or treatment does not always exist.
Risk group 4: high individual risk for the worker with a high probability of spreading to the community. They have a high potential for transmission from one individual to another. They can cause serious diseases in humans for which there are no effective means of prophylaxis or treatment.