Introduction to Health and Safety at Work

14.3 
Forms of biological agent
As with chemicals, biological hazards may be trans-
ported by any of the following forms of agent.
Fungi
are very small organisms, sometimes consisting of 
a single cell, and can appear as plants (e.g. mushrooms 
and yeast). Unlike other plants, they cannot produce 
their own food but either live on dead organic matter or 
on living animals or plants as parasites. Fungi reproduce 
by producing spores which can cause allergic reactions 
when inhaled. The infections produced in man by fungi 
may be mild, such as athlete’s foot, or severe such as 
ringworm. Many fungal infections can be treated with 
antibiotics.
Moulds
are a particular group of very small fungi which, 
under damp conditions, will grow on surfaces such as 
walls, bread, cheese, leather and canvas. They can be 
benefi cial (penicillin) or cause allergic reactions (asthma). 
Asthma attacks, athlete’s foot and farmer’s lung are all 
examples of fungal infections.
Bacteria
are very small single-celled organisms which 
are much smaller than cells within the human body. 
They can live outside the body and be controlled and 
destroyed by antibiotic drugs. There is evidence that 
bacteria are becoming resistant to most antibiotics. This 
has been caused by the widespread misuse of antibiot-
ics. It is important to note that not all bacteria are harm-
ful to humans. Bacteria aid the digestion of food and 
babies would not survive without their aid to break down 
the milk in their digestive systems. Legionella, tubercu-
losis and tetanus are all bacterial diseases.
Viruses
are minute non-cellular organisms which can 
only reproduce within a host cell. They are very much 
smaller than bacteria and cannot be controlled by antibi-
otics. They appear in various shapes and are continually 
developing new strains. They are usually only defeated by 
the defence and healing mechanisms of the body. Drugs 
can be used to relieve the symptoms of a viral attack but 
cannot cure it. The common cold is a viral infection as 
are hepatitis, AIDS (HIV) and infl uenza.