Annexure B : Hazardous Biological Agents Guidelines

Categorisation of Biological Agents according to Hazard and Categories of containment

Introduction

1) The attached list must be read in conjunction with the Hazardous biological Agents, and in particular regulation 3.

2) Agents listed are categorised on the basis of their ability to cause disease by infection.

3) In allocating agents to a hazard group in the list no account is taken of particular effects on those whose susceptibility to infection may be affected for one or other reason such as pre-existing disease, medication, compromised immunity, pregnancy or breastfeeding. Additional risk to such workers should be considered as part of the assessment required by the Hazardous Biological Agents.

4) Biological agents that have not been classified for inclusion into Group 2 to 4 in the list are not implicitly classified in Group I.

5) If more than one species of any particular agent is known to be pathogenic to humans, the most prominent of these is generally named, together with the wider reference 'species' (spp) to indicate the fact that the other species of the same genus may be hazardous. If a whole genus is mentioned in this way, it is implicit that species and strains that are non-pathogenic to humans are excluded.

6) When a strain is attenuated or has lost known virulence genes, the containment required by the classification of its parent strain need not necessarily apply, subject to assessment appropriate to the risk in the workplace, for example when such strain is used as a product or as part of a product for prophylactic or therapeutic purposes. (See 2)

7) All viruses that have been isolated in humans and that have not been assessed and allocated to a group in the list are to be classified in Group 2 as a minimum, except where there is evidence that they are unlikely to cause disease in humans.

8) The requirements as to containment consequent upon the classification of parasites apply only to stages in the life cycle of the parasite in which it is liable to be infectious for humans.

9) The list also gives a separate indication where biological agents are capable of causing allergic or toxic reactions, where an effective vaccine is available.

The following notations identify the indications -

A: Possible allergic effects;
T: Toxin production;
V: Effective vaccine available;
NIV: National Institute of Virology.

The selection of control measures for biological agents should take into account the fact that there is no exposure limits for them. Their ability to replicate and to infect at very small doses means that exposure may have to be reduced to levels that are diminishingly low.

For each activity the first consideration should be whether it could be carried out in a way that involves exposure to a less harmful biological agent. This may be practicable, for example, in teaching and some types of research. If there is more than one way of carrying out the activity then the method carrying the least risk should be chosen.

If the least harmful alternative still involves exposure or potential exposure to biological agent, or the nature of the activity is such that there is no choice, and it is not reasonably practicable to prevent exposure by some other means, then exposure should be adequately controlled. All of the measures listed in Annexure E should be considered, and each should be used where and to the extent that -

1. it is applicable; and
2. the assessment carried but under regulation 6 shows that it will lead to a non-negligible reduction in risk.

Not all the listed measures will be required in every case. The assessment may indicate, for example, that a specific mode of transmission and route of infection is required, a susceptible host is needed, there is low prevalence of the infection in that particular activity, and that illness is easily treatable, leading to rapid and complete recovery.

In such a case the risk would be relatively low and the control measures required less stringent. Another factor that will determine whether controls are to be applied will be the extent to which the activity involves the handling or deliberate use of a biological agent, or exposure is incidental to the main purpose of the work. However, the level of risk should be the principal consideration - if the risk is sufficiently high and can be reduce by some of the listed measures, they should be applied in full.

Certain special measures are required in health and veterinary care facilities, laboratories, animal rooms and industrial processes to ensure that biological agents are not transmitted to workers or outside the controlled area. For laboratories, animal rooms and industrial processes rules are laid down for the derivation of containment level from the hazard classification of the agent, or from what is suspected about the possible presence of an agent. Laboratories screening for an agent which falls in Group 3 and 4, but which is not ordinarily expected to be present (for example a microbiological laboratory in a food factory screening for salmonella, with the possibility of finding Salmonella typhi), should achieve at least containment level 2, but switch to the appropriate higher level if the agent is found and if work is to continue with it. In a laboratory that does not deliberately work with biological agents, but where the presence of agents calling for containment levels 3 or 4 is nevertheless known or suspected, those containment levels should be used.

Agents with reduced virulence may be used at a lower than normal level of containment if the alteration has effectively changed their classification.

A biological agent that falls or is treated as falling into Hazard Group I may be a Group 3 genetically modified organism, because of environmental risks associated with it or because, though now unlikely to cause human disease, it is derived by genetic modification from a pathogenic parental organism. In the latter case, the selection of containment measures appropriate to the agent's reduced virulence and corresponding group may be permitted. Where there is a mismatch, as in the case of a genetically modified organism or biological agent which is non-hazardous to humans, but environmentally harmful, more stringent requirements should be followed.

Where the rules as set out lead to a particular containment level for an activity, all the measures appropriate to that level should normally be used. Some selection may be done, however, to suit individual circumstances, provided that the risk is not increased by doing so.

Regulation 11 sets out additional requirements in respect of personal protective equipment used to protect employees against biological agents. The object of these requirements is to prevent the equipment itself from acting as the means by which agents are transmitted, and they should be followed accordingly.

Where workers are exposed to biological agents the information and instructions given to them, if applicable, should be set down in the form of written instructions, outlining procedures to be followed after a serious incident involving the handling of a biological agent as well as the procedure for handling any Group 4 agent.

If the nature of the workplace and the activity are such that employees may need instant access to this information, or where a reduction in risk may be expected by having the information conspicuously displayed in the workplace, it should also be set out on notices displayed in the workplace.

Bacteria

Key:
A: allergic effects
T: Toxic effects
V: Vaccine available
NIV: National Institute of Virology

Viruses

- Including strains isolated from cats and exotic species e.g. elephants, cheetahs.
- Including strains originally classified as rabbitpox virus.
- All strains including "whitepox virus"

Parasites