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Biological Health Hazard – (Report) Large Legionellosis Outbreak 2015-16: Castilla-La Mancha, Spain


Published Date: 2016-11-12 12:37:39
Subject: PRO/EDR> Legionellosis – Spain (03): (CM) outbreak 2015-16, report, fountain susp
Archive Number: 20161112.4624561

Administrative Map of Spain

Administrative Map of Spain – Between Extremadura and the Valencian Community lies Castilla-La-Mancha, formerly part of the Kingdom of Castile. The autonomous community comprises five provinces: Albacete, Ciudad Real, Cuenca, Guadalajara, and Toledo. Capital city is Toledo.

Date: Monday 7 November 2016
Source: 20minutos [in Spanish, trans. Kathryn Soderholm, edited]

It is clear from the report on the outbreak delivered this Monday [7 Nov 2016] in the Cortes of Castilla-La Mancha that the outbreak recorded in Manzanares had “the highest attack rate of any community outbreak of legionellosis published in the scientific literature”.

The conclusions of this report, published by Europa Press, stated that the rapid intervention of the Directorate General of Public Health of Castilla-La Mancha “along with the immediate activation of the area’s health services allowed them to minimize the effects of the disease and interrupt the transmission of legionella in the shortest possible time.”

The report emphasized the collaboration between the different administrations, highlighting “the support of professionals and institutions from other autonomous communities, as well as the Coordinating Center for Health Alerts and Emergencies (CCAES), National Epidemiology Center (CNE) and National Center for Microbiology (CNM).”

According to the epidemic curve, the period of maximum exposure could have occurred between 1 and 14 Dec [2015], although from the middle of November an “intermittent dripping of cases” had been recorded.

The fatality rate of this outbreak “is one of the lowest of those recorded in community outbreaks” of this type, although the study understands that an ageing population and the prevalence of risk factors “could contribute to the risk of illness, which could partly explain the high rate of attack”. The report highlights that although the entire population was subjected to the same risk, “there was no case recorded in children under 15 years” and only 2 in people under 25.

It is also pointed out that the absence of a meteorological station in the village prevented rigorous investigation into environmental causes, although reports from the State Agency “state that unusually high temperatures were registered in the province in November and December [2015],” citing the phenomenon of thermal inversion as “a cause for the maintenance in the environment of infectious aerosols of legionella”.

The cases were concentrated in the north of the municipality, where most of the risky facilities [cooling towers?] were located, and 12 different strains were identified in respiratory samples [determined how, by genotyping?].

In addition, the report explains that the investigation of environmental samples “had many difficulties and poor performance,” and in most facilities at risk, legionella was detected, “although it only could be sequenced [whole genome sequencing?] in 2 of them.”

Thus, in one of the cooling towers examined, strain ST 899 was identified, but “it appears that it did not function during the exposure period. To know for sure whether it worked or not could be a very important element in research.”

The report, presented on Monday [7 Nov 2016] in parliament, shows that the epidemiological models that best explain most of the cases of the outbreak, but not all, are those corresponding to the bus station fountain. “The presence of legionella in non-negligible concentrations was detected both in the reservoir and in the jets of the bus station fountain, although no strain could be sequenced. The technical services hired by the City of Manzanares were able to isolate a strain that was not linked to the outbreak, at least with confirmed cases,” the experts said.

communicated by:
ProMED-ESP and Kathryn Soderholm

[Manzanares is a municipality, with a population of 18 924 in 2014, in the province of Ciudad Real, in the autonomous community of Castile-La Mancha, Spain (,_Ciudad_Real). A map of Spain showing the location of Manzanares can be found at,+Cdad.+Real,+Spain/.
A HealthMap/ProMED-mail map can be found at:

At the time of the 1st report of this outbreak on 14 Dec 2015 (ProMED-mail. Legionellosis – Spain (02): (CM) 20151217.3869362), there were only 5 cases of legionnaires’ disease in the city of Manzanares. About 2 weeks later, there were 228 confirmed cases, with 2 deaths (ProMED-mail. Legionellosis – Spain: (CM) large outbreak, fatal, update 20160103.3907865). All suspected sources (cooling towers and an ornamental fountain at the Manzanares bus station) had been closed, and as of that report, no new case had appeared after 25 Dec 2015.

We are told in the above news report that in a final report to parliament “12 different strains of legionella” (species unidentified) were found, presumably by DNA typing, in respiratory specimens. We are not told how many respiratory isolates were genotyped and whether any had matching genotypes, but nevertheless this suggests that this outbreak did not have a common source for all the cases and that there may be 12 different sources.

We are also told in the news report above that, despite the presence of legionella in most of the suspected sources, genotyping could only be done in 2 environmental samples and the genotype of 1 of the 2 did not match that of any clinical sample. We are not told if the genotype of the other matched that of a clinical isolate.

Nevertheless, “epidemiological models” best explained the bus station’s ornamental fountain as the source for most of the cases of the outbreak, but not all, even though isolates of legionella from the fountain in “non-negligible concentrations” could not be genotyped. – Mod.ML

A HealthMap/ProMED-mail map can be accessed at:]

See Also

Legionellosis – Spain (02): (CT) fatal, hotel 20161008.4545840
Legionellosis – Spain: (CM) large outbreak, fatal, update 20160103.3907865

Legionellosis – Spain (03): (CM) large outbreak, fatal 20151224.3889986
Legionellosis – Spain (02): (CM) 20151217.3869362

A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases


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