Biological agents are classified into four groups according to the level of risk of infection they present:
1° Group 1 includes biological agents that are unlikely to cause disease in humans;
2° Group 2 includes biological agents that may cause disease in humans and constitute a danger to workers. Their spread in the community is unlikely and effective prophylaxis or treatment is generally available;
3° Group 3 includes biological agents which can cause serious illness in humans and constitute a serious danger for workers. Their spread in the community is possible, but there is generally effective prophylaxis or treatment;
4° Group 4 comprises biological agents which cause serious illness in humans and constitute a serious danger for workers. The risk of their spreading in the community is high. There is generally no effective prophylaxis or treatment.