Environmental Engineering Reference
In-Depth Information
looked for in that component. Notable microor-
ganisms missing from Table 21.1 include Leptos-
pira spp. and Shigella spp., both of which are likely
to be found in some flood components in the UK.
.
Reports of aerosol flood-related infection are
rare, although a small outbreak of Legionnaire's
disease has been associated with a flood incident
(Kool et al. 1998). In theUSA, the owner, awaitress
and a regular customer of a bar became ill with
Legionnaire's disease; investigations revealed that
the only common exposure for the cases was the
bar, which had been flooded nine days before the
first reported illness. Legionella pneumophila,of
the same serotype isolated from the cases, was
isolated from the sump in the crawlspace under
the bar and from a hose running from the sump to
the street. Following the flooding, water was
pumped from beneath the bar to the street over
a period of three days by an old electrical sump
pump. The pump generated a considerable
amount of heat while running and it is thought
that this may have provided temperatures favour-
able to the growth of Legionella. This, in conjunc-
tion with an aerosol generated from a jet of water
coming from a small hole in the side of the pump,
was probably responsible for the outbreak.
.
In terms of likely infection in any flooded pop-
ulation, the most probable route of exposure to
flood-associated pathogens is by accidental
ingestion. There is epidemiological evidence of
infection resulting from direct contact with flood
waters. For example, an outbreak of norovirus
infection (a relatively mild, self-limiting stomach
upset) in American tourists in Salzburg, Austria,
revealed a link with direct exposure to flood
water contaminated with raw sewage (Schmid
et al. 2005). Following heavy exposure to the flood
waters during the clean-up, 49 of 64 people in the
party (77%) succumbed to a gastrointestinal
illness later diagnosed as norovirus infection. The
infections were thought to be contracted through
direct contact with the flood water, followed by
secondary person-to-person transmission.
.
After the cessation of flooding and the com-
pletion of the clean-up process, ingestion of soil
may be a potentially important route of exposure
to flood-deposited pathogens, via recreational
activities, gardening and the consumption of
home-grown foods (Davis and Mirick 2006).
Young children may be at particular risk of
pathogen ingestion from soils due to their
Pathways or Routes of Exposure
A person may be exposed to microorganisms in
floodwaters and sediments through various routes
during the flood itself, throughout any clean-up
procedures and also, in some cases, after the
remediation period when flooded residences are
reinhabited. Exposuremay be via threemain path-
ways: ingestion, inhalation or skin (or wound)
infection.
.
Skin or wound infection is most likely to occur
either during the flood (e.g. during evacuation), or
in the immediate period of remediation when
people would potentially be directly exposed to
flood waters and, thus, experience contact with
water. Reports of flood-related infection via this
route are uncommon, although in the USA a fatal
case of septicaemia (blood poisoning) in a 57-year-
old man was attributed to infection of an open
wound and contact with flood water (Spice 2004).
The victim was also diabetic, which would have
made him more susceptible to infection.
.
Inhalation of microorganisms may occur during
floodingandtheremediationperiod,viafloodwater
sprays and airborne water droplets. It is also possi-
ble that some pathogens, such as noroviruses and
Mycobacterium avium complex (MAC), may re-
main in house dusts after the flood waters have
dried, although there is little evidence to suggest
significant survival of these pathogens. Inhalation
ofmouldandfungalgrowth, inparticular,mayhave
implications for respiratory health. Immunocom-
promised people may be at risk of systemic infec-
tion, and exposure tohomemoulds is thought to be
a factor leadingtocasesof bronchialasthma, chron-
ic allergic rhinitis, hypersensitivity pneumonitis
and sick building syndrome (Kramer et al. 2000).
However, although the growth of mould and fungi
may be a consequence of flood inundation, it is not
related to thepathogencontent of floodwaters, and
is not considered further here.
