How to classify biological agents?

Earlier we presented the nature of biological agents as one of the possible factors that can adversely affect human health. Could you give some examples?

Among these micro-organisms, several types can be identified, such as: bacteria; fungi and viruses; single and multicellular parasites; animal vectors used as intermediate hosts.

How dangerous are they?

Each of these agents is characterised by properties that, taken together, also determine its degree of dangerousness: it is on this basis that a proper classification of biological agents takes place. These properties are listed below:

• INFECTIVITY - ability of a biological agent to penetrate and multiply in an organism: infection does not necessarily evolve into full-blown disease. For some biological agents, infectious doses have been defined, i.e. the number of micro-organisms needed to cause infection.

• PATHOGENICITY - ability to induce disease after infecting an organism; depends on factors such as toxin production and ability to overcome defence systems.

• TRANSMISSIBILITY - the likelihood that the biological agent will be transmitted from an infected person to a healthy one. It can occur directly (e.g. through blood) or indirectly, through inanimate materials (air, water, biological materials, dust, clothing, food, waste, surfaces and equipment) or vectors, such as certain arthropods (mosquitoes, ticks, etc.) and rodents.

• NEUTRALISATION - availability of preventive and therapeutic measures specific to a given biological agent: disinfectants, drugs, vaccines.

Biological agents are then classified into four groups of increasing hazard, which are analysed in the table below.

When to wear PPE?

Where the application of collective prevention and protection measures does not allow the elimination of all risks (so called residual risks remain), it is necessary to adopt specific Individual Protection Devices (PPE) to prevent the different modes of infection.

• body protection
• hand protection
• eye protection
• respiratory protection

Stay informed, stay safe.