LEGIONELLA - World Health Organization

Proteins produced by the body’s immune system that recognize and help fight infections and other foreign
substances in the body.
c A serogroup is a subdivision of a species or subspecies distinguishable from other strains on the basis
of antigenic character testing for recognizable antigens on the surface of the microorganism.
d Antigens are foreign substances that stimulate the production of antibodies by the immune system.
e Seroconversion is the development of antibodies in blood serum as a result of infection or immunization.
f Cases of legionellosis acquired during travel (e.g. from a cruise ship or a hotel).
g European Working Group for Legionella Infections (EWGLI) 1 definition, introduced in January 2001.
h This is a working definition: the decision to follow up cases will be made locally or nationally.
i Community clusters or community-acquired cases are those that are not travel-acquired, health-care acquired
or domestically acquired (i.e. acquired in the patient’s home).
Table . Category of European cases, – 00
Category
of cases
Year
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS
000 00 00 00 00
Nosocom al 151 157 105 215 181 195 275 333 277 347 309
Commun ty 186 270 617 388 478 679 659 1475 1767 2106 1884
Travel
assoc ated 190 194 246 290 297 439 500 674 944 927 984
Not known 634 634 595 451 486 823 722 988 1691 1072 1369
Total 0
Source: Information obtained from the European Working Group for Legionella Infections (EWGLI) 2
1.2.1 Community-acquired pneumonia
The term “community-acquired pneumonia” (CAP) refers to cases that are not acquired through
travel, health care or the domestic setting. CAPs have a high rate of hospital admission, with
less than 1% being managed at home. Legionnaires’ disease can account for up to 30% of
CAPs requiring admission to intensive care (Woodhead et al., 1987; Macfarlane et al., 1993).
In recent studies involving hospitalized patients with CAP in the United States of America
(USA), Europe, Israel and Australia, 0.5–10% had Legionnaires’ disease, with an average
level of about 2% (NHMRC, 1988; Fang et al., 1990; Rello et al., 1993; Mundy et al., 1995;
Olaechea et al., 1996; Marston et al., 1997; Stout and Yu, 1997; Boldur et al., 1999; Cosentini
et al., 2001; Lim et al., 2001; Fields, Benson & Besser, 2002; Mandell et al., 2002; Mandell et al.,
2004; Edelstein & Cinaciotto, 2005). The proportion of CAPs resulting in severe pneumonia
1 http://www.ewgli.org/
2 http://www.ewgli.org/