LEGIONELLOSIS - AUSTRALIA: (VICTORIA) FATAL, COOLING TOWER SUSPECTED
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A ProMED-mail post
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International Society for Infectious Diseases
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Date: Thu 24 Jan 2013
Source: ABC News [edited]
<http://www.abc.net.au/news/
A man is dead, and 4 others have been treated in hospital after a
Legionnaires' disease outbreak in Footscray, in Melbourne's west.
A man aged in his 50s who had other significant medical conditions
died early today [24 Jan 2013] at Western Hospital. Three other people
have been discharged after recovering from the flu-like illness, while
another remains in hospital.
Health Department officials are testing and disinfecting about 2 dozen
air-conditioning cooling towers in Footscray.
Legionnaires' disease is acquired through breathing in very fine
droplets of water that contain the bacteria, such as spray drifts
which are vented off from cooling towers. The acting chief health
officer, Dr Michael Ackland, says all the patients spent time in an
area within a 2-km radius of central Footscray. Dr Ackland says
thorough decontamination and cleaning of infected towers should
eliminate the disease, and there is no longer any risk to the public.
"There should be no risk to people travelling in the Footscray area
now, as all the cooling towers are now being disinfected, cleaned and
rendered safe," he said.
But he says anyone in the area who has been unwell and has flu-like
symptoms should go to their doctor. "Legionnaires' disease can take 10
days to manifest itself after an exposure," he said. "So if indeed any
of the cooling towers that we are examining are ultimately found to be
the cause of this problem, then, yes, people may well come forward as
new cases." Dr Ackland says the cases were individually reported
between 8 Dec 2012 and yesterday [23 Jan 2013], when the common link
to the Footscray area was confirmed.
A 56-year-old St Albans man, a 93-year-old Yarraville woman, and a
69-year-old Footscray man have been treated in hospital and
discharged. A 75-year-old West Footscray woman is still in hospital.
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Communicated by:
Alexandra Volosinas
<alexandra.volosinas@gmail.com
[The following is extracted from moderator ML's comments in
ProMED-mail post Legionellosis - Australia: (VI) cooling tower susp
20121204.1436695:
Legionellosis is an infectious disease caused usually by inhalation of
aerosols containing _Legionella_ species. Legionnaires' disease is the
acute pneumonic form of legionellosis; more than 70 percent of cases
of legionnaires' disease are due to _L. pneumophila_ serogroup 1,
except in Australia and New Zealand, where _L. pneumophila_ serogroup
1 has accounted for only 45.7 percent of cases of community-acquired
legionellosis, and _Legionella longbeachae_ has accounted for 30.4
percent of cases (Yu VL, et al: Distribution of _Legionella_ species
and serogroups isolated by culture in patients with sporadic
community-acquired legionellosis: An international collaborative
survey. J Infect Dis. 2002; 186(1): 127-8. Available at
<http://www.legionella.org/lp_
disease due to _L. longbeachae_ has been associated with the use of
potting soil and gardening.
The news report above does not say how the diagnosis of legionnaires'
disease was made or what species of _Legionella_ was implicated in the
5 cases, but presumably it is _L. pneumophila_, a water-borne
pathogen, since a cooling tower is being tested as a possible source.
A diagnosis of even a single case of legionnaires' disease implies the
presence of an environmental source to which other susceptible
individuals are likely to have been exposed. It is, therefore, a
public health imperative to find that source to prevent further cases.
The effect of wind speed and direction on _Legionella_-contaminated
plumes from cooling towers may influence the distribution of cases.
Genotyping of patient and environmental isolates has become a helpful
tool to establish transmission pathways. The predominance of one
genotype of _Legionella_ isolated from patient specimens would suggest
transmission from a common source. Because _Legionella_ may be found
in environmental samples without linkage to any cases of
legionellosis, the actual causative infectious reservoir can be
confirmed by matching the genotype of clinical and environmental
isolates (see <http://www.ncbi.nlm.nih.gov/
<http://www.ncbi.nlm.nih.gov/
However, this is difficult in legionellosis outbreaks, because,
frequently, the diagnosis of legionnaires' disease is made only on the
basis of urinary _L. pneumophila_ serogroup 1 antigen testing or
serology, rather than isolation of the organism from cultures of
respiratory tract specimens. Consequently, clinical isolates are often
not available for genotyping.
Footscray, with a population of 13 203 (2011), is a suburb 5 km (3.1
miles) west of Melbourne, Victoria, Australia
