Communicable diseases

Communicable diseases are those that are transmissible from
one person, or animal, to another. The disease may be spread
directly, via another species (vector) or via the environment.
Illness will arise when the infectious agent invades the host,
or sometimes as a result of toxins produced by bacteria in
food.
The spread of disease through a population is determined
by environmental and social conditions which favour the
infectious agent, and the relative immunity of the
population. An outbreak of infection could endanger the
operation and safety of the ship. An understanding of the
disease and the measures necessary for its containment and
management is therefore important.
Infectious agents and examples of
diseases
The organisms that cause disease vary in size from viruses,
which are too small to be seen by a light microscope to
intestinal worms which may be over a metre long. The groups
of infectious agents are listed with examples of diseases they
cause.
Bacteria
Pneumonia, tuberculosis, enteric fever, gonorrhoea
Viruses
Measles, varicella, influenza, colds, rabies
Fungi
Ringworm, tinea pedis (athlete’s foot)
Protozoa
Malaria, giardia
Metazoa
Tapeworm, filariasis, onchcerciasis (river blindness),
hookworm
Prions
Kuru, Creutzfeld-Jacob disease, Bovine spongiform
encephalopathy (BSE)
Modes of transmission
Direct transmission
n Direct contact with the infected person as in touching,
kissing or sexual intercourse
n Droplet spread through coughing sneezing, talking or
explosive diarrhoea
n Faecal-oral spread when infected faeces is transferred to
the mouth of a non infected person, usually by hand.
Indirect transmission
n Indirect transmission of infectious organisms involves
vehicles and vectors which carry disease agents from the
source to the host.