LEGIONELLA - World Health Organization

Exposure histories allow cases to be grouped into the following categories:
• community acquired
• domestically acquired
• nosocomial (i.e. health-care acquired)
• travel associated.
For surveillance purposes, cases should be reported to the relevant national centre after the
exposure history has been obtained. An example of a national surveillance report form is given
in Appendix 3.
Table 1.3 in Chapter 1 provides some useful definitions for epidemiological monitoring at
the national level and for comparing exposure risks at the international level; it also defines
community clusters and outbreaks.
In the presence of a pneumonic illness, a laboratory diagnosis will support or refute clinical
suspicion of Legionella infection and will help to classify the case. Table 9.1 summarizes the
patient dataset required for surveillance of Legionnaires’ disease. The dataset should include
as many of the items shown in Table 9.1 as possible.
Table . Dataset for surve llance of leg onellos s
Surve llance dataset
Demograph c h story
Comment
Patient age or date of birth Age is an important moderator for acquiring the disease
Gender Reported incidence is two to three times higher
in men than women
Home address or area of residence May indicate a local source of exposure
Occupation and occupation address
Cl n cal h story
May indicate an increased risk of exposure
Date of onset of symptoms for Relevant to the exposure history and date
Legionella infection
of specimen for laboratory diagnosis
Other relevant medical history A recent organ transplant or other causes of immunosuppression,
recent surgery, a history of smoking or
high alcohol intake, all increase individual susceptibility
Date and place of hospital admission Helpful if clinical advice is needed for follow-up of
illness outcome
Outcome of illness Serves as an index of severity and case–fatality ratio
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS