Legionnaires' Disease Cases Research Articles

Characterization of the extent of a large outbreak of Legionnaires' disease by serological assays.

BackgroundIn May 2005, a long-distance outbreak of Legionnaires’ disease (LD) caused by Legionella pneumophila serogroup 1 occurred in south-east Norway. The initial outbreak investigation without serology identified 56 laboratory-confirmed LD cases of whom 10 died. However, 116 patients with community-acquired pneumonia might belong to the outbreak based on epidemiological investigations, but acute laboratory tests other than serology were negative or not performed. To assess the true extent of the outbreak, we evaluated two serological assays in order to reclassify the 116 patients with indeterminate case status.MethodsTwo polyvalent antibody tests, a serogroup 1–6 immunofluorescence assay (IFA) and a serogroup 1–7 enzyme-linked immunosorbent assay (ELISA) were used. They were evaluated with cases defined as culture- or urinary antigen positive LD patients (n = 40) and non-cases defined as confirmed non-LD patients (n = 39) and healthy control subjects (n = 62). The 116 patients, who were negative in culture, polymerase chain reaction and/or urinary antigen tests, were analysed by the same serological assays. Antibodies to the outbreak strain were determined by immunoblotting.ResultsIn the evaluation study, the sensitivity and specificity of a ≥4-fold IFA titre change was 38% and 100%, respectively, with corresponding values of 30% and 99% for seroconversion in ELISA. A single high positive IFA titre yielded sensitivity and specificity of 73% and 97%, respectively, with corresponding values of 68% and 96% for a single high immunoglobulin (Ig) G and/or IgM in ELISA.Based on this evaluation, the following serological testing identified 47 more LD cases, and the outbreak thus comprised 103 cases with a case fatality rate of 10%. About the same proportion (70%) of the urinary antigen positive and negative LD cases had antibodies to the serogroup-specific lipopolysaccharide of the outbreak strain. In addition to the 103 LD cases, Legionella infection could not be verified or excluded in 32 patients based on epidemiology and/or lack of microbiological sampling.ConclusionsThe acute-phase tests (culture, polymerase chain reaction, and urinary antigen) identified less than 55% of the 103 patients in this outbreak. Serological testing thus remains an important supplement for diagnosis of LD and for determination of outbreak cases.

The importance of clinical surveillance in detecting legionnaires' disease outbreaks: a large outbreak in a hospital with a Legionella disinfection system-Pennsylvania, 2011-2012.

Healthcare-associated Legionnaires' disease (LD) is a preventable pneumonia with a 30% case fatality rate. The Centers for Disease Control and Prevention guidelines recommend a high index of suspicion for the diagnosis of healthcare-associated LD. We characterized an outbreak and evaluated contributing factors in a hospital using copper-silver ionization for prevention of Legionella growth in water. Through medical records review at a large, urban tertiary care hospital in November 2012, we identified patients diagnosed with LD during 2011-2012. Laboratory-confirmed cases were categorized as definite, probable, and not healthcare associated based on time spent in the hospital during the incubation period. We performed an environmental assessment of the hospital, including collection of samples for Legionella culture. Clinical and environmental isolates were compared by genotyping. Copper and silver ion concentrations were measured in 11 water samples. We identified 5 definite and 17 probable healthcare-associated LD cases; 6 case patients died. Of 25 locations (mostly potable water) where environmental samples were obtained for Legionella-specific culture, all but 2 showed Legionella growth; 11 isolates were identical to 3 clinical isolates by sequence-based typing. Mean copper and silver concentrations were at or above the manufacturer's recommended target for Legionella control. Despite this, all samples where copper and silver concentrations were tested showed Legionella growth. This outbreak was linked to the hospital's potable water system and highlights the importance of maintaining a high index of suspicion for healthcare-associated LD, even in the setting of a long-term disinfection program.

Analysis of severe Legionellosis hospitalized in intensive care units in Tunisia

This study is the first one that describes the situation of Legionnaires' disease (LD) in Tunisia, with its clinical and epidemiological characteristics and investigates the risk factors associated with Legionella infections in our country. We conducted a retrospective multicentric study during 5 years (2008-2012) concerning all confirmed LD cases in Tunisia and we investigated risk factors for infection. The total of confirmed LD cases was 14. Incidence was 0.03. Mean age: 53.1, sex ratio (M/F): 2.6. Summer-autumnal peak was noted. Risk factors for infection were: the great humidity at home (n=4), living in community (n=3) and practice ablutions (before prayer) in public places (n=4). Community acquired legionellosis (n=9) and nosocomial (n=2). Pulmonary symptoms (n=11)+/-gastrointestinal (n=6) and/or neurological signs (n=4). Beta lactams therapy failed (n=11). CXR showed bilateral lesions (n=6). Abnormalities in laboratory values were noted: hyponatremia (n=9), high CPK levels (n=9). Diagnosis was confirmed by positive urinary Legionella antigens test (n=10) and by direct immunofluorescence (n=1). Treatment was based on bitherapy (n=10). Five patients died. The incidence of LD appears lower than other countries. Some risk factors, as ablutions, are different from that reported in Western countries and seem to be specific to our society. Given the seriousness of its consequences, it is strongly recommended to improve the national surveillance system up and register LD as notifiable disease.

Epidemiologic characteristics associated with ST23 clones compared to ST1 and ST47 clones of Legionnaires disease cases in France.

In France, approximately 1200 cases of Legionnaires disease (LD) are reported annually, and isolates are available for approximately 20% of cases identified since 2000. All Legionella pneumophila serogroup 1 (sg1) isolates are characterized by sequence-based typing at the National Reference Centre. LD cases caused by L. pneumophila sg1 reported from 2008 through 2012 were considered for the study. Our study objective was to describe cases according to their sequence type (ST). We also constructed multivariable modified Poisson regression models to estimate the incidence rate ratio (IRR) and to identify characteristics potentially associated with ST23 clones compared to ST1 and ST47 clones. We studied 1192 patients infected by ST1 (n = 109), ST23 (n = 236), ST47 (n = 123) or other STs (n = 724). The geographic distribution of the ST23 cases across the country was significantly different compared to other ST groups. This genotype was significantly associated with the absence of corticosteroid therapy compared to ST1 (IRR = 0.56; p 0.016). Concerning exposure, the ST23 genotype was significantly less associated with hospital-acquired infections compared to ST1 (IRR = 0.32; p 0.001), but it was more associated with infections acquired in hospitals and elderly settings compared with ST47. Finally, the ST23 genotype was less frequently associated with travel than other STs. Despite the large number of cases of ST23 infection, we did not identify any characteristics specific to this ST. However, we identified independent associations between ST1 and nosocomial transmission and steroid therapy. These findings should encourage further exploration, especially in terms of environmental diffusion, strain virulence and host factors.

Summer increase of Legionnaires' disease 2010 in The Netherlands associated with weather conditions and implications for source finding

During August and September 2010 an unexpected high number of domestic cases of Legionnaires' disease (LD) were reported in The Netherlands. To examine this increase, patient characteristics and results of source finding and environmental sampling during the summer peak were compared to other domestic cases in 2008-2011. This analysis did not provide an explanation for the rise in cases. A similar increase in LD cases in 2006 was shown to be associated with warm and wet weather conditions, using an extended Poisson regression model with adjustment for long-term trends. This model was optimized with the new data from 2008 to 2011. The increase in 2010 was very accurately described by a model, which included temperature in the preceding 4 weeks, and precipitation in the preceding 2 weeks. These results confirm the strong association of LD incidence with weather conditions, but it remains unclear which environmental sources contributed to the 2010 summer increase.

Legionnaires’ disease caused by Legionella longbeachae in Taiwan, 2006–2010

The aim of the present study was to investigate the epidemiology of Legionnaires' disease (LD) caused by Legionella longbeachae in Taiwan during 2006-2010. A total of six cases were identified prospectively, accounting for 1.6% of all laboratory-confirmed LD cases and 4.4% of culture-positive LD cases. All six cases occurred between April and August. The male to female ratio was 0.5. These six LD patients had a higher median age than those with LD due to Legionella pneumophila. Four of the six patients presented with pleural effusion and five survived the infection episode. Only two patients had a potential soil contact history prior to LD onset. The patients resided in divergent geographical areas without a common exposure history. The individual genomic DNA banding patterns of the six L. longbeachae isolates analyzed by pulsed-field gel electrophoresis (PFGE) were unique, supporting the hypothesis that the L. longbeachae infections occurred sporadically.

Prevalence of sequence types among clinical and environmental isolates of Legionella pneumophila serogroup 1 in the United States from 1982 to 2012.

Since the establishment of sequence-based typing as the gold standard for DNA-based typing of Legionella pneumophila, the Legionella laboratory at the Centers for Disease Control and Prevention (CDC) has conducted routine sequence-based typing (SBT) analysis of all incoming L. pneumophila serogroup 1 (Lp1) isolates to identify potential links between cases and to better understand genetic diversity and clonal expansion among L. pneumophila bacteria. Retrospective genotyping of Lp1 isolates from sporadic cases and Legionnaires' disease (LD) outbreaks deposited into the CDC reference collection since 1982 has been completed. For this study, we compared the distribution of sequence types (STs) among Lp1 isolates implicated in 26 outbreaks in the United States, 571 clinical isolates from sporadic cases of LD in the United States, and 149 environmental isolates with no known association with LD. The Lp1 isolates under study had been deposited into our collection between 1982 and 2012. We identified 17 outbreak-associated STs, 153 sporadic STs, and 49 environmental STs. We observed that Lp1 STs from outbreaks and sporadic cases are more similar to each other than either group is to environmental STs. The most frequent ST for both sporadic and environmental isolates was ST1, accounting for 25% and 49% of the total number of isolates, respectively. The STs shared by both outbreak-associated and sporadic Lp1 included ST1, ST35, ST36, ST37, and ST222. The STs most commonly found in sporadic and outbreak-associated Lp1 populations may have an increased ability to cause disease and thus may require special attention when detected.

A TLR6 polymorphism is associated with increased risk of Legionnaires’ disease

Legionella pneumophila (Lp), the etiologic agent of Legionnaires’ Disease (LD), is an important cause of community-acquired and nosocomial pneumonia. However, the host immune and genetic determinants of human susceptibility to Lp are poorly understood. Here we show that both TLR6 and TLR1 cooperate with TLR2 to recognize Lp in transfected HEK293 cells. We also perform a human genetic association study of 14 candidate single nucleotide polymorphisms in Toll-like receptors (TLRs) 1, 2, and 6 in 98 LD cases and 268 controls from the Netherlands. No polymorphisms in TLR1 or TLR2 were associated with LD. A TLR6 polymorphism, 359T>C (rs5743808), was associated with an elevated risk of LD in genotypic and dominant (OR 5.83, p=7.9×10−5) models. The increased risk in persons with 359 TC or CC genotypes was further enhanced among smokers. In a multivariate model, 359T>C was associated with a higher risk of LD (OR 4.24, p=0.04), than any other variable, including age and smoking. Together, these data suggest that the human TLR6 variant, 359T>C, is an independent risk factor for LD.

Legionnaires’ disease case-finding algorithm, attack rates, and risk factors during a residential outbreak among older adults: an environmental and cohort study

BackgroundDuring a Legionnaires’ disease (LD) outbreak, combined epidemiological and environmental investigations were conducted to identify prevention recommendations for facilities where elderly residents live independently but have an increased risk of legionellosis.MethodsSurvey responses (n = 143) were used to calculate attack rates and describe transmission routes by estimating relative risk (RR) and 95% confidence intervals (95% CI). Potable water collected from five apartments of LD patients and three randomly-selected apartments of residents without LD (n = 103 samples) was cultured for Legionella.ResultsEight confirmed LD cases occurred among 171 residents (attack rate = 4.7%); two visitors also developed LD. One case was fatal. The average age of patients was 70 years (range: 62–77). LD risk was lower among residents who reported tub bathing instead of showering (RR = 0.13, 95% CI: 0.02–1.09, P = 0.03). Two respiratory cultures were characterized as L. pneumophila serogroup 1, monoclonal antibody type Knoxville (1,2,3), sequence type 222. An indistinguishable strain was detected in 31 (74%) of 42 potable water samples.ConclusionsManagers of elderly-housing facilities and local public health officials should consider developing a Legionella prevention plan. When Legionella colonization of potable water is detected in these facilities, remediation is indicated to protect residents at higher risk. If LD occurs among residents, exposure reduction, heightened awareness, and clinical surveillance activities should be coordinated among stakeholders. For prompt diagnosis and effective treatment, clinicians should recognize the increased risk and atypical presentation of LD in older adults.

Legionnaires’ disease in Italy: results of the epidemiological surveillance from 2000 to 2011

According to the Italian Surveillance System for Legionnaires' disease (LD), physicians must fill in a form for every case and send it through the Local Health Units to the National Institute of Health (Istituto Superiore di Sanità, ISS). Forms reported in the period from 2000 to 2011 were analysed and discussed. A total of 9,803 cases of LD were reported to ISS during the study period. The median age of cases was 63 years, with a ratio male/female of 2.6 and a case fatality rate of 11.8%. The number of cases has been steadily increasing from 192 cases in 2000 to 1,235 in 2010 and 1,008 cases in 2011. The reported cases showed a geographical gradient, with the highest number notified in the north and the lowest in the south. The majority of cases (73.0%) were community-acquired, followed by travel-associated (13.5%) and healthcare-associated cases (9.3%), cases acquired in long-term care facilities (2.1%), and other types of exposure (2.1%). Even though the increasing trend of LD in Italy indicates an improvement in the ability to detect and report cases, the geographical gradient highlights the existence of low reporting areas where the epidemiological surveillance of LD should be further strengthened.

Two years' performance of an in-house ELISA for diagnosis of Legionnaires' disease: Detection of specific IgM and IgG antibodies against Legionella pneumophila serogroup 1, 3 and 6 in human serum

The aim of this study was to evaluate the performance of an in-house ELISA for the diagnosis of Legionnaires' disease (LD) by detection of IgM and IgG antibodies against Legionella (L.) pneumophila serogroups (sg) 1, 3 and 6. The evaluation was done throughout a two-year period in a diagnostic routine laboratory. Furthermore, the sensitivity of four different methods, the in-house L. pneumophila antibody test (ELISA), the urinary antigen test (Binax® EIA), an in-house PCR and culture, both alone and in combination was evaluated.From 2008 to 2010, 12,158 serum samples from 10,503 patients were analysed. During the same period, 361 cases of laboratory-confirmed LD cases were recorded in Denmark, but of these only 113 had a serum sample examined. The positive predictive value of the in-house ELISA was calculated to be 12.8 and the negative predictive value was 99.6, using only the confirmed LD cases as true positives.The sensitivity of the in-house ELISA for the detection of IgM and IgG antibodies in the confirmed LD cases was 61% and 36%, respectively. By combining the two ELISA assays the sensitivity increased to 66%. The sensitivity of the Legionella urinary antigen test (Binax® EIA) was 63%, of the in-house PCR 87% and of culture 69%. When all the different methods were combined, a higher sensitivity was calculated — for in-house ELISA (IgM+IgG) and Binax® EIA 91%, in-house ELISA (IgM+IgG) and in-house PCR 93%, in-house ELISA (IgM+IgG) and culture 93%, Binax® EIA and in-house PCR 79%, Binax® EIA and culture 68% and in-house PCR and culture 94%.This study confirms that the detection of IgG and IgM antibodies by ELISA is an important diagnostic tool, also during the initial phase of the disease. Furthermore, we showed that LD in Denmark with or without serum samples collected exhibits the same age and sex distribution and epidemiology, as in the rest of Europe, i.e., mostly men are infected, infections are mostly community acquired, followed by infection from travelling abroad. Apart from patients with notified LD, the patients investigated by serology were evenly distributed in all age groups; there was only a slightly higher ratio of men tested for “atypical pneumonia” in the serology laboratory.

Evaluation of a Legionella Outbreak Emerged in a Recently Opening Hotel

Legionnaires' disease (LD) is a systemic infection caused by Legionella species especially colonized in the water systems. Hotels are common locations in which waterwork-associated sporadic or epidemic legionellosis can be detected. The aim of this study was to evaluate a small Legionella outbreak emerged in a recently opened 600-bed hotel in Alanya, a touristic county in Mediterranean part of Turkey. A 66 years old male patient who stayed in this hotel opened on May 15th, 2009, was admitted to our hospital on May 21st, 2009 with the complaints of high fever, headache and diarrhea lasting for three days. Since chest X-ray revealed non-homogenous density increase in left middle and inferior zone, the patient was diagnosed as atypical pneumoniae and LD was confirmed by positive urinary Legionella antigen test (Card test, BinaxNOW®Legionella Urinary Antigen Test; Alere Co, USA) result. Following the identification of the index case, the records of our hospital were reviewed and revealed another case being treated with the diagnosis of community acquired pneumonia who was also the guest of the same hotel. This patient was then diagnosed as LD by positive urinary antigen test. Since new cases were identified during the following days (May 22, 25 and 26) the Antalya County Health Department and hotel management were informed about a cluster of LD. In addition subsequent investigation for environmental surveillance and water sampling were conducted. The LD diagnosis and environmental inspections were performed according to the procedure described in the guideline from "Turkish Ministry of Health Travel-Associated Legionnaires' Disease Control Programme". Five definitive cases and one presumptive case of LD were identified during the outbreak period (May 20-26, 2009). All of the cases were successfully treated (intravenous ciprofloxacin or levofloxacin or clarithromycin), however one patient died due to sudden death during sleep after being discharged. Since sputum samples could not be obtained from the cases, the diagnosis were not confirmed by culture but by urinary antigen test. Besides high antibody titer in single serum sample was accepted as a diagnostic marker. Additionally 26 cases who accommodated in the same hotel and presented with high fever without pneumonia were treated in the outpatient clinics of our hospital. Urinary antigen test was performed in 11 of those patients to confirm the prediagnosis of pontiac fever, however all were found negative. Likewise convalescent phase sera for the confirmation of the diagnosis by seroconversion could not be obtained since they all were foreign tourists. Investigation of water sources of the hotel revealed that the municipal drinking water network had not been connected yet and the hotel supplied water from groundwater sources. The analysis of multiple samples from multiple sites of hotel's water system indicated that the water temperature was between 35-45°C and the iron level was beyond the acceptable limits (245 µg/L) recommended for drinking water in the regulation guides. These properties were considered as the factors that enhanced the growth and survival of Legionella species. Water samples were cultivated on BCYE-_ (Buffered Charcoal Yeast Extract a-Ketoglutarate) and GVPC (Glycine-Vancomycin-Polymyxin-Cycloheximide) agar plates and 11 out of a total 13 samples yielded Legionella spp. growth. All isolates were identified as L.pneumophila serogroup 1 by specific antisera. Legionella decontamination of hotel's water system was managed by implementation of hyperchlorination method as well as superheating (> 60°C) of water. The hotel was not closed during the outbreak and cultures of water samples obtained for one year later did not yield any Legionella spp. growth. This outbreak emphasized that hotel residents are at risk for acquiring LD in the presence of a colonized water system, even in a newly constructed building. In conclusion, effective control and decontamination programmes for the prevention of Legionella colonization should be applied even in new opening hotels.

Legionnaires' disease in France: sensitivity of the mandatory notification has improved over the last decade

The notification rate of Legionnaires' disease (LD) in France was 2.4/100 000 population in 2010, varying across regions with an increasing rate from west to east. Two sources [mandatory notifications (MN) and a survey of hospital laboratories] were used in a capture-recapture study to estimate the number of LD cases and the sensitivity of the MN system at national and regional levels in 2010. The number of missed cases was estimated using Chapman's method. The estimated sensitivity of MN was 88.5% (95% CI 88.0-89.0) and ranged from 70% to 100% by region. The estimated incidence was 2.7/100 000 population. Sensitivity of the MN system improved since the previous capture-recapture estimates (10% in 1995, 33% in 1998). This study confirmed that the observed west-east gradient is not related to regional notification disparities. Ecological studies should be conducted to better understand the observed spatial variations in LD incidence.

Meteorological factors and risk of community-acquired Legionnaires’ disease in Switzerland: an epidemiological study

ObjectivesThe aim of this study was to identify meteorological factors that could be associated with an increased risk of community-acquired Legionnaires’ disease (LD) in two Swiss regions.DesignRetrospective epidemiological study using...

Meteorological conditions and incidence of Legionnaires' disease in Glasgow, Scotland: application of statistical modelling

This study investigated the relationships between Legionnaires' disease (LD) incidence and weather in Glasgow, UK, by using advanced statistical methods. Using daily meteorological data and 78 LD cases with known exact date of onset, we fitted a series of Poisson log-linear regression models with explanatory variables for air temperature, relative humidity, wind speed and year, and sine-cosine terms for within-year seasonal variation. Our initial model showed an association between LD incidence and 2-day lagged humidity (positive, P = 0·0236) and wind speed (negative, P = 0·033). However, after adjusting for year-by-year and seasonal variation in cases there were no significant associations with weather. We also used normal linear models to assess the importance of short-term, unseasonable weather values. The most significant association was between LD incidence and air temperature residual lagged by 1 day prior to onset (P = 0·0014). The contextual role of unseasonably high air temperatures is worthy of further investigation. Our methods and results have further advanced understanding of the role which weather plays in risk of LD infection.

Application of Legionella pneumophila-specific quantitative real-time PCR combined with direct amplification and sequence-based typing in the diagnosis and epidemiological investigation of Legionnaires’ disease

The detection of Legionella pneumophila DNA in clinical specimens using quantitative real-time polymerase chain reaction (qPCR) combined with direct sequence-based typing (SBT) offers rapid confirmation and timely intervention in the investigation of cases of Legionnaires' disease (LD). We assessed the utility of a specific L. pneumophila qPCR assay targeting the macrophage infectivity potentiator (mip) gene and internal process control with three clinical specimen types from confirmed LD cases. The assay was completely specific for L. pneumophila, as demonstrated by positive results for 39/39 strains from all subspecies and 16 serogroups. No cross-reaction was observed with any of the 54 Legionella non-pneumophila (0/69 strains) or 21 non-Legionella (0/58 strains). All L. pneumophila culture-positive respiratory samples (81/81) were qPCR-positive. Of 80 culture-negative samples tested, 47 (58.8%) were qPCR-positive and none were inhibitory. PCR was significantly more sensitive than culture for samples taken ≤ 2 days of hospitalisation (94.7% vs. 79.6%), with the difference being even more marked for samples taken between 3 and 14 days (79.3% vs. 47.8%). Overall, the sensitivity of the qPCR was ∼30% greater than that of culture and direct typing on culture-negative PCR-positive samples resulted in full 7-allele profiles from 23/46, 5 to 6 alleles from 8/46 and ≥ 1 allele from 43/46 strains.

Diagnostic testing for Legionnaires’ disease in the Netherlands between 2007 and 2009: a possible cause for the decline in reported Legionnaires’ disease patients

Legionnaires' disease (LD) is an acute pneumonia caused by the inhalation or aspiration of aerosols contaminated with the Legionella bacteria. In the Netherlands, around 300 LD cases per year were reported between 2000 and 2008, but in 2009, the number dropped to 251, which was the lowest number in the previous 5 years of surveillance. We investigated if this decrease could be explained by the number of performed Legionella diagnostic tests in this year. We analyzed the number of tests performed between 2007 and 2009 in three large microbiological laboratories in different geographical regions in the Netherlands. Our data showed that there was no decrease in the number of patients for whom a diagnostic test for Legionella was performed in this period. These results are not in line with our hypothesis that the decrease in reported Legionella pneumonia patients in 2009 would be due to a decrease in patients for whom a diagnostic test was performed. We conclude that it is more likely that other factors such as the influence of weather patterns might explain the sudden drop in reported Legionella pneumonia patients in 2009 compared to the previous years, and it would be interesting to investigate this for the period described.

Mortality of hospital or community-acquired Legionnaires’ disease (LD): a prospective study

The clinical aspects and outcome of hospital (HA) and community-acquired (CA) cases of LD might be different. We explored these topics in 267 patients with LD hospitalized in France.

Epidemiologie der Legionärskrankheit in Deutschland

Legionnaires' disease (LD) is a severe form of pneumonia which is caused by bacteria of the genus Legionella. They are widespread in fresh water and can also colonize technical water systems where they might present an infection risk. Since 2001, notification of laboratory-confirmed LD is mandatory in Germany. From 2001-2009, a total of 3672 cases of LD were registered. During the first 7 years, case numbers increased (2001: 127; 2007: 536 cases) but have remained stable during the past 2 years (2008: 525; 2009: 503 cases). In 2009, 49.6% of cases were attributed to an infection in the community, 33.2% were travel associated, and 13.6% were nosocomial. The average case fatality rate between 2001 and 2009 was 6.5%. However, the case fatality rate of nosocomial cases was three times as high compared to cases with non-nosocomial exposure. The network for community-acquired Legionnaires' disease (CAPNETZ) estimates that there are 20,000 cases per year in Germany. Thus, the number of reported cases represents only a small proportion of the actually occurring cases. It is likely that specific LD-diagnostics are insufficiently used. Hence, physicians should test more patients with pneumonia for LD. In particular, because of the high case fatality, nosocomial pneumonia cases need to be tested; identified LD cases require rigorous investigational and corrective action. In order to obtain evidence-based data on the relationship of water contamination and the risk for LD, it would be desirable, if (in addition to the patients' epidemiological data) the results of water texts relating to a given case were also reported systematically.

Progress in the surveillance and control of Legionella infection in France, 1998–2008

In France, the notification of Legionnaires' disease (LD) has been mandatory since 1987. Following a study showing an important under-reporting of the disease, the surveillance system was strengthened in 1997: the urinary antigen detection test was introduced as a new diagnostic tool and guidelines for prevention and control of the disease were implemented. After these measures, the incidence of LD increased gradually, reaching 2.5 per 100,000 in 2005, and then slightly decreased (2.0 per 100,000 in 2008). Data from the mandatory notification system and from the national reference centre for Legionella were analysed. Analysis covered the 1998-2008 period. During the period 1998-2008 a total of 11147 cases of LD were reported in France through the mandatory system. The majority of cases were diagnosed by urinary antigen test. The median age of cases was 61 years, the male to female ratio was 2.9, and the case fatality rate was 13%. Exposure during travel was documented for 17% of cases. A hospital-acquired infection was suspected for 9% of cases, and this percentage decreased from 21% in 1998 to 7% in 2008. Over this period, 14 community outbreaks were identified involving 380 cases, and cooling towers were the most probable source of infection for 13. No outbreak was reported in 2008. Registration at the regional level of all cooling towers became mandatory at the end of 2004, and the 1997 prevention and control guidelines were updated in 2005. In recent years, several regulations have also been implemented in the hospital setting and care homes for the elderly. All these measures have contributed to strengthen the French surveillance system and improve our ability to better prevent, detect, and control LD.