Another 2 persons have been admitted to hospital with legionnaires' disease in the greater
The health board reported 3 cases last week [week of 24 Jun 2013], with 2 of the patients having been released from hospital and the 3rd described as in a stable condition and responding well to treatment.
Health experts have identified Renfrew as a common factor in all 5 cases and investigations into the source of the disease are being focused on the town. 2 of the 5 cases live in the Renfrew area and the other 3 cases have either visited or worked there during the 2-week incubation period of the disease.
Dr Gillian Penrice, NHSGGC [National Health Service Greater Glasgow and
Legionnaires' disease is an uncommon but serious form of pneumonia, caused by bacteria distributed widely in natural and artificial water supplies. The symptoms include headache, fever, dry cough, breathing difficulties, stomach pains, and diarrhoea. The health board said water cooling towers in the Renfrewshire area are being treated with chemicals as a precautionary measure. Samples from water supplies are also being examined but test results will not been known for some time, it said.
Dr Penrice added: "It is important to remember _Legionella_ cannot be spread from person to person. _Legionella_ cannot be contracted by drinking contaminated water and residents in the Renfrew area should continue to drink water and prepare food in the normal way."
An outbreak of the disease in southwest
Communicated by: ProMED-mail
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.
_L. longbeachae_ is found in soil and potting mix (Ross IS, Mee BJ, Riley TV: _Legionella longbeachae_ in Western Australian potting mix.
Med J Aust 1997; 166(7): 387), and legionnaires' disease due to _L.
longbeachae_ has been associated with the use of potting soil and unlike _L. longbeachae_, _L. pneumophila_ is found in water sources, such as natural aquatic bodies, including rivers, lakes, and thermally polluted waters.
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 cooling towers are being tested as possible sources.
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
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.
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