01. Legionnaires’ disease

Question 1

Legionellosis is a collective term for diseases caused by legionella bacteria
including the most serious legionnaires’ disease, as well as the similar but less
serious conditions of

Answer 1

Pontiac fever and Lochgoilhead fever

Question 2

Legionnaires’ disease
is a potentially fatal form of pneumonia and everyone is susceptible to infection.
The risk increases with age, but some people are at higher risk, eg

Answer 2

eg people over 45, smokers and heavy drinkers,
people suffering from chronic respiratory or
kidney disease,
diabetes,
lung and heart disease anyone with an impaired
immune system.

Question 3

The bacterium Legionella pneumophila and related bacteria are common in
natural water sources such as rivers, lakes and reservoirs, but usually in low
numbers. They may also be found in purpose-built water systems, such as

Answer 3

cooling

towers, evaporative condensers, hot and cold water systems and spa pools

Question 4

Legionnaires’ disease is normally contracted by inhaling small droplets of
water (aerosols), suspended in the air, containing the bacteria. Certain conditions
increase the risk from legionella if:

Answer 4

(a) the water temperature in all or some parts of the system may be between
20–45 °C, which is suitable for growth;
(b) it is possible for water droplets to be produced and if so, they can be
dispersed;
(c) water is stored and/or re-circulated;
(d) there are deposits that can support bacterial growth, such as rust, sludge,
scale, organic matter and biofilms.