LEGIONELLA - World Health Organization

1.1.2 Pontiac fever
Symptoms
Pontiac fever is an acute, self-limiting, influenza-like illness without pneumonia (that is, it is
“non-pneumonic”). Unlike Legionnaires’ disease, Pontiac fever has a high attack rate, affecting
up to 95% of exposed individuals (Glick et al., 1978). The main symptoms are listed in
Table 1.1.
Radiographic changes and long-term effects
Chest X-rays are normal, and recovery within one week is usual.
Incubation period
The incubation period is 24–48 hours.
Diagnosis and treatment
Treatment is supportive and aimed at relieving symptoms; complications rarely occur.
Causative agents
Depending on the causative agent, Pontiac fever may, in rare cases, not be as benign as previously
thought (Jones et al., 2003). For example, Spieker et al. (1998) reported a case of acute
disseminating encephalomyelitis that developed three weeks after a flu-like infection (Pontiac
fever) with L. cincinnatiensis. Pontiac fever has also been associated with production of endotoxins
(Fields et al., 2001).
Endotoxins can be extremely toxic to people, producing fever, shock and even death. It is not
uncommon to find endotoxin associated with high heterotrophic plate counts (tests used to
estimate the total number of all types of bacteria in an environmental sample). Therefore,
further study is needed to establish whether endotoxin has a role in causing Pontiac fever
where legionellae are also present. An outbreak in Scotland with Pontiac fever symptoms was
caused by L. micdadei, and was named Lochgoilhead fever (Goldberg et al., 1989). Section 1.4
discusses the causative agents in more detail.
1.1.3 Extrapulmonary syndromes
It has been shown by autopsy that L. pneumophila can spread from the respiratory system to
the body. Legionellae have been detected in the spleen, liver, kidney, myocardium, bone and
bone marrow, joints, inguinal and intrathoracic lymph nodes and digestive tract (Lowry &
Tompkins, 1993).
Table 1.2 provides details of cases of extrapulmonary syndromes associated with Legionella species.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS