LEGIONELLA - World Health Organization

2.4.2 Disease spread via soil
In a number of documented cases of legionellosis, no aquatic source was implicated. In these
cases, likely sources of infection have been potting soils and soil conditioners. Most reports
of soil-derived infection since the 1990s identify L. longbeachae as the infectious agent (Steele,
Lanser & Sangster, 1990; Steele, Moore & Sangster, 1990; Koide et al., 1999). The mode of
transmission of these infections remains unclear.
Anecdotal reports suggest possible links between building excavations and outbreaks of
legionellosis (Miragliotta et al., 1992; Mermel et al., 1995). These outbreaks may be due to
increased dispersion of dust during earthmoving operations, since dust entering cooling towers
adds nutrients and surfaces for bacterial growth and may also interfere with biocide action.
Alternatively, the outbreaks may be due to interference in the water supply, which allows
contamination by bacteria, including legionellae.
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS