Incidence Of Legionellosis Research Articles

Modern features of legionellosis

BACKGROUND: Community-acquired Legionella pneumonia, classified as atypical pneumonia, is an important problem worldwide. Late initiation of etiotropic therapy for Legionnaires’ disease worsens the prognosis and increases the risk of death.
 AIM: To clinically and epidemiologically characterize Legionnaires’ disease using data on its incidence in the Krasnodar region and to attract the attention of doctors to its timely diagnosis and the prescription of adequate etiotropic therapy.
 MATERIALS AND METHODS: A hospital cohort of 26 patients who were hospitalized between 2017 and 2022 was studied for legionellosis, which was confirmed in the laboratory by the detection of Legionella antigen in the urine using immunochromatography.
 RESULTS: The Krasnodar region is characterized by a sporadic incidence of legionellosis, which tends to increase in periods with high average humidity. Cases of legionellosis are recorded throughout the year, with peaks in summer and winter. The rise in incidence shifts annually and follows the month with the highest rainfall and average monthly temperature 20°C. Severe and moderate courses of legionellosis typically occur in men aged 50 years, with comorbid pathology and accompanied by lung damage of varying severity levels. Some patients may experience diarrhea (11.5%) and transient liver and kidney dysfunction. The nature of lung damage, such as polysegmental pneumonia, does not have clear clinical differential diagnostics, which makes early diagnosis difficult. An epidemiological anamnesis indicating contact with aerosol water, soil, and air conditioning systems has important diagnostic significance. Seeking specialized medical care after the 7th day of illness increases the risk of developing severe disease with complications.
 CONCLUSIONS: In severe community-acquired pneumonia, the epidemiological history must be considered, kidney and liver function should be assessed, a urine test must conducted for Legionella antigens, and early empirical therapy with fluoroquinolones and macrolides must be initiated.

Increased Incidence of Legionellosis after Improved Diagnostic Methods, New Zealand, 2000–2020

Legionellosis, notably Legionnaires' disease, is recognized globally and in New Zealand (Aotearoa) as a major cause of community-acquired pneumonia. We analyzed the temporal, geographic, and demographic epidemiology and microbiology of Legionnaires' disease in New Zealand by using notification and laboratory-based surveillance data for 2000‒2020. We used Poisson regression models to estimate incidence rate ratios and 95% CIs to compare demographic and organism trends over 2 time periods (2000-2009 and 2010-2020). The mean annual incidence rate increased from 1.6 cases/100,000 population for 2000-2009 to 3.9 cases/100,000 population for 2010-2020. This increase corresponded with a change in diagnostic testing from predominantly serology with some culture to almost entirely molecular methods using PCR. There was also a marked shift in the identified dominant causative organism, from Legionella pneumophila to L. longbeachae. Surveillance for legionellosis could be further enhanced by greater use of molecular typing of isolates.

Effect of the COVID-19 pandemic and state of emergency declarations on the relative incidence of legionellosis and invasive pneumococcal disease in Japan

IntroductionDuring the COVID-19 pandemic, the incidence of many droplet-transmitted infections decreased due to increased mask-wearing and social distancing. Contrastingly, there has been concern that COVID-19 countermeasures, such as lockdowns, may increase legionellosis incidence via water stagnation. During the pandemic in Japan, four state of emergency declarations were imposed between 2020 and 2021, which makes it particularly suitable to test this hypothesis. MethodsWe use country-level surveillance data from the National Institute of Infectious Diseases to track the relative incidence of legionellosis compared to invasive pneumococcal disease (IPD) during the COVID-19 pandemic in Japan, with a focus on the periods just after state of emergency declarations were lifted. ResultsThe absolute number of legionellosis and IPD cases decreased in 2020 and 2021 compared to previous years. The average relative incidence of legionellosis as well as the variance of the relative incidence significantly increased during the pandemic compared to previous years. There were no increases in the relative incidence of legionellosis during the periods immediately following emergency declaration liftings, but the relative incidence did increase considerably during the first two states of emergency. ConclusionsCOVID-19 countermeasures appear more effective at decreasing the incidence of human-to-human transmitted infections, such as IPD, compared to environmentally-transmitted infections, such as legionellosis. Though no evidence was found to suggest that legionellosis cases increased after state of emergency declarations, public health efforts should continue to emphasize the importance of routine sanitation and water system maintenance to prevent water stagnation and Legionella spp. contamination.

Epidemiological and clinical characteristics of legionellosis in Northern Australia, 2010–2021

Objective This study describes characteristics of the legionellosis cases occurring between 2010 and 2021 in the Northern Territory (NT), Australia. Methods We retrospectively reviewed 53 cases of legionellosis during the defined period and documented patient and clinical characteristics, diagnostics, and seasonality of infection. Results All cases were sporadic. The incidence rate in the NT was higher than the Australian median rate (2.1 and 1.5 per 100,000 population per year respectively). Aboriginal and Torres Strait Islander patients presented at a younger age than did non-Indigenous patients (median 41 and 60 years of age respectively), and overall there was a male preponderance. There was a higher proportion of legionellosis in the months with increased humidity, with a greater number of L. longbeachae infections detected overall (59%) than of L. pneumophila (41%). The majority of cases were diagnosed serologically (57% of L. pneumophilia and 93% of L. longbeachae ). Conclusions Legionellosis in the NT is more common, seasonal, and may be underreported due to current reliance on serological testing for diagnosis. The higher incidence of legionellosis, and the younger age of Aboriginal and Torres Strait Islander patients of the NT, have public health implications, given that the clinical presentation of legionellosis is indistinguishable from other forms of pneumonia.

Effects of climate changes and road exposure on the rapidly rising legionellosis incidence rates in the United States.

Legionellosis is an infection acquired through inhalation of aerosols that are contaminated with environmental bacteria Legionella spp. The bacteria require warm temperature for proliferation in bodies of water and moist soil. The legionellosis incidence in the United States has been rising rapidly in the past two decades without a clear explanation. In the meantime, the US has recorded consecutive years of above-norm temperature since 1997 and precipitation surplus since 2008. The present study analyzed the legionellosis incidence in the US during the 20-year period of 1999 to 2018 and correlated with concurrent temperature, precipitation, solar ultraviolet B (UVB) radiation, and vehicle mileage data. The age-adjusted legionellosis incidence rates rose exponentially from 0.40/100,000 in 1999 (with 1108 cases) to 2.69/100,000 in 2018 (with 9933 cases) at a calculated annual increase of 110%. In regression analyses, the rise correlated with an increase in vehicle miles driven and with temperature and precipitation levels that have been above the 1901–2000 mean since 1997 and 2008, respectively, suggesting more road exposure to traffic-generated aerosols and promotive effects of anomalous climate. Remarkably, the regressions with cumulative anomalies of temperature and precipitation were robust (R2 ≥ 0.9145, P ≤ 4.7E-11), implying possible changes to microbial ecology in the terrestrial and aquatic environments. An interactive synergy between annual precipitation and vehicle miles was also found in multiple regressions. Meanwhile, the bactericidal UVB radiation has been decreasing, which also contributed to the rising incidence in an inverse correlation. The 2018 legionellosis incidence peak corresponded to cumulative effects of the climate anomalies, vast vehicle miles (3,240 billion miles, 15904 km per capita), record high precipitation (880.1 mm), near record low UVB radiation (7488 kJ/m2), and continued above-norm temperature (11.96°C). These effects were examined and demonstrated in California, Florida, New Jersey, Ohio, and Wisconsin, states that represent diverse incidence rates and climates. The incidence and above-norm temperature both rose most in cold Wisconsin. These results suggest that warming temperature and precipitation surplus have likely elevated the density of Legionella bacteria in the environment, and together with road exposure explain the rapidly rising incidence of legionellosis in the United States. These trends are expected to continue, warranting further research and efforts to prevent infection.

РЕЗУЛЬТАТЫ ОБСЛЕДОВАНИЯ ИСКУССТВЕННЫХ ВОДНЫХ СИСТЕМ ГОСТИНИЧНЫХ КОМПЛЕКСОВ ГОРОДА АЛМАТЫ НА КОНТАМИНИРОВАННОСТЬ LEGIONELLA PNEUMOPHILA

Legionellosis is a sapronous acute infectious disease, with a mortality rate of about 10% in the pulmonary form, caused by various types of microorganisms belonging to the genus Legionella. According to current data, about 90% of legionellosis is associated with the species L. pneumophila. The main habitat of Legionella is abiotic environmental objects. Legionella in the majority of cases is sown from respiratory therapy equipment, air conditioning fluids, home and industrial cooling systems, shower and boiler installations. Observations have shown that the incidence of legionellosis in travelers is slightly higher than in people who do not change their location. The purpose of this work was to study the contamination of L. pneumophila in artificial water systems of four hotels in Almaty. Flushes from various objects of water systems and water samples were selected as the material for analysis. Bacteriological studies of the samples did not yield positive results. A PCR study of 30 samples revealed 4 positive samples in one of the hotels. It was found that the water temperature in the hot water system does not exceed 40-60°C all year round. The optimal temperature in water use systems for bacterial growth is 25-60°C. Key words: Legionellosis, Legionella, PCR, gene sections, bacteriology, molecular genetic method.

Culture of Clinical Specimens Reveals Extensive Diversity of Legionella pneumophila Strains in Arizona.

Between 2000 and 2017, a total of 236 Legionella species isolates from Arizona were submitted to the CDC for reference testing. Most of these isolates were recovered from bronchoalveolar lavage specimens. Although the incidence of legionellosis in Arizona is less than the overall U.S. incidence, Arizona submits the largest number of isolates to the CDC for testing compared to those from other states. In addition to a higher proportion of culture confirmation of legionellosis cases in Arizona than in other states, all Legionellapneumophila isolates are forwarded to the CDC for confirmatory testing. Compared to that from other states, a higher proportion of isolates from Arizona were identified as belonging to L. pneumophila serogroups 6 (28.2%) and 8 (8.9%). Genome sequencing was conducted on 113 L. pneumophila clinical isolates not known to be associated with outbreaks in order to understand the genomic diversity of strains causing legionellosis in Arizona. Whole-genome multilocus sequence typing (wgMLST) revealed 17 clusters of isolates sharing at least 99% identical allele content. Only two of these clusters contained isolates from more than one individual with exposure at the same facility. Additionally, wgMLST analysis revealed a group of 31 isolates predominantly belonging to serogroup 6 and containing isolates from three separate clusters. Single nucleotide polymorphism (SNP) and pangenome analysis were used to further resolve genome sequences belonging to a subset of isolates. This study demonstrates that culture of clinical specimens for Legionella spp. reveals a highly diverse population of strains causing legionellosis in Arizona which could be underappreciated using other diagnostic approaches.IMPORTANCE Culture of clinical specimens from patients with Legionnaires' disease is rarely performed, restricting our understanding of the diversity and ecology of Legionella Culture of Legionella from patient specimens in Arizona revealed a greater proportion of non-serogroup 1 Legionellapneumophila isolates than in other U.S. isolates examined. Disease caused by such isolates may go undetected using other diagnostic methods. Moreover, genome sequence analysis revealed that these isolates were genetically diverse, and understanding these populations may help in future environmental source attribution studies.

Legionellosis in Poland in 2017

The aim of this study is to assess the epidemiological situation of legionellosis in Poland in 2017 in comparison with previous years. The analysis is based on national surveillance data published in the annual bulletin: “Infectious diseases and poisonings in Poland in 2017” and bulletins from previous years along with data from legionellosis case reports collected and sent to the Department of Epidemiology of Infectious Diseases and Surveillance NIPH – NIH by Sanitary and Epidemiological Stations. In Poland, both cases of Legionnaires’ disease (an acute form of infection with pneumonia) and Pontiac fever (a mild, influenza-like form of infection) are routinely reported to the surveillance system. In 2017, a total of 39 cases of legionellosis were registered, including 38 cases of Legionnaires’ disease and 1 case of Pontiac fever; the annual incidence rate 0.102 (per 100,000 population) has increased by almost 50 percent since previous year (0.070) and is almost three times higher than the median incidence (0.036) for 2011-2015. The infections were reported in fourteen voivodeships; only one voivodeship (Świętokrzyskie) did not register any case in last years. The incidence in men (0.129 per 100,000) was higher compared to women (0.076); the highest incidence (0.323) was noted in men aged 50-59. All reported cases were sporadic and were hospitalised. The Sanitary Inspection reported nine fatal cases – 6 women and 3 men. Thirty three cases were autochthonous including four cases linked with contaminated water systems in health-care settings. Six cases were associated with travels abroad (to Egypt, Albania, Italy and Crete). Although in recent years number of reported cases continues to rise, the incidence of legionellosis in Poland remains one of the lowest in the entire EU. Also draws attention variation of incidence between provinces and a high mortality among reported cases. Our data suggest significant under-diagnosis of legionellosis. A priority remains to improve early diagnosis of Legionnaires’ disease in health care settings.

Analysis of population-level determinants of legionellosis: spatial and geovisual methods for enhancing classification of high-risk areas

BackgroundAlthough the incidence of legionellosis throughout North America and Europe continues to increase, public health investigations have not been able to identify a common exposure in most cases. Over 80% of cases are sporadic with no known source. To better understand the role of the macro-environment in legionellosis risk, a retrospective ecological study assessed associations between population-level measures of demographic, socioeconomic, and environmental factors and high-risk areas.MethodsGeographic variability and clustering of legionellosis was explored in our study setting using the following methods: unadjusted and standardized incidence rate and SaTScan™ cluster detection methods using default scanning window of 1 and 50% as well as a reliability score methodology. Methods for classification of “high-risk” census tracts (areas roughly equivalent to a neighborhood with average population of 4000) for each of the spatial methods are presented. Univariate and multivariate logistic regression analyses were used to estimate associations with sociodemographic factors: population ≥ 65 years of age, non-white race, Hispanic ethnicity, poverty, less than or some high school education; housing factors: housing vacant, renter-occupied, and built pre-1950 and pre-1970; and whether drinking water is groundwater or surface water source.ResultsCensus tracts with high percentages of poverty, Hispanic population, and non-white population were more likely to be classified as high-risk for legionellosis versus a low-risk census tract. Vacant housing, renter-occupied housing, and homes built pre-1970 were also important positively associated risk factors. Drinking water source was not found to be associated with legionellosis incidence.DiscussionCensus tract level demographic, socioeconomic, and environmental characteristics are important risk factors of legionellosis and add to our understanding of the macro-environment for legionellosis occurrence. Our findings can be used by public health professionals to target disease prevention communication to vulnerable populations. Future studies are needed to explore the exact mechanisms by which these risk factors may influence legionellosis clustering.

Implementation of a Legionella Ordinance for Multifamily Housing, Garland, Texas.

Context:The incidence of legionellosis has sharply increased in the United States as a result of contaminated water systems. Jurisdictions across the country are considering whether to develop and implement regulations to protect individuals against Legionnaires' disease with its associated high morbidity and mortality.Objective:This article sheds light on the implementation and effectiveness of a 2005 citywide Legionella testing mandate of multifamily housing cooling towers in Garland, Texas. This ordinance has been in place for more than 10 years and represents the first of its kind in the United States to mandate routine testing of cooling towers for Legionella in multifamily housing.Design, Setting, and Population:We utilized a mix of both qualitative and quantitative methods to explore the development, adoption, and implementation of the ordinance. Phone interviews were conducted with individuals from the City of Garland Health Department and apartment managers. Quantitative data included public health surveillance data on legionellosis.Main Outcome Measures:Barriers and facilitators of implementation, number and percentage of cooling towers from multifamily housing units that tested positive for Legionella by year, and number of legionellosis cases by year in Garland, Texas.Results:Study outcomes highlight key themes that facilitated the successful implementation of the Legionella testing mandate, including the importance of timing, leadership support, stakeholder engagement, and education and outreach. The number of contaminated cooling towers was reduced over time.Conclusion:Mandatory monitoring for legionella in a local jurisdiction may result in reduced risk of legionellosis from cooling towers through raising awareness and education of building owners and managers about the need to prevent, detect, and remediate legionella contamination in their building water systems. Garland, Texas, broke new ground in the United States in moving toward primary prevention of legionellosis. The ordinance may be useful both in serving to educate and increase awareness about the need for Legionella prevention and to monitor effectiveness of maintenance procedures.

Legionella risk assessment in cruise ships and ferries.

<b>Introduction.</b> The increasing development of marine traffic has led to a rise in the incidence of legionellosis among travellers. It occurs in similar environments, especially closed and crowded, and aboard ships Legionella survives and multiplies easily in water pipes, spreading into the environment through air conditioning systems and water distribution points. Although in recent years in the construction of cruise ships preventive measures aimed at curbing the proliferation of Legionella (design, materials, focus on the operation and maintenance of the water system), have been taken account, little or no attention has been paid to small ships which, in many cases, are old and not well maintained. <b>Objective.</b> The aim of the study was to evaluate the frequency and severity of Legionella contamination in ferries and cruise ships in order to adopt more specific control measures. <b>Materials and method.</b> A prevalence study was carried out on 10 ferries and 6 cruise ships docking or in transit across the port of Messina (Sicily, Italy). Water and air samples collected from many critical points were tested for qualitative and quantitative identification of Legionella. <b>Results and conclusions.</b> Legionella pneumophila sg 1 was isolated from the samples of shower and tap water in 7 (70%) of the 10 ferries examined, and in 3 (33%) of the 6 cruise ships examined, and L.pneumophila sg 2-14 in 8 (80%) and 1 (16.7%) of these ships, respectively. No Legionella contamination was found in whirlpool baths, air and ice samples. In conclusion, the data obtained confirm higher levels of Legionella contamination in local ferries and cruise ships, underlining the need to adopt corrective actions more specific for these smaller vessels.

Is Legionellosis Present and Important in Colombia? An Analyses of Cases from 2009 to 2013.

Infection due to Legionella pneumophila has been not studied in Colombia, although it is present. The observational, retrospective study in which the incidence of legionellosis in Colombia, 2009-2013, was estimated based on data extracted from the personal health records system (Registro Individual de Prestación de Servicios, RIPS) using the ICD-10 codes A48.1 (Legionnaires' disease) and A48.2 (Pontiac Fever). Using official population estimates of the National Administrative Department of Statistics (DANE), crude and adjusted incidence rates were estimated (cases / 100,000 pop). During the period, 206 cases were reported (mean of 41.2 per year) for the cumulated national rate of 0.45 cases / 100,000 pop. The clinical form of legionellosis with the highest incidence rates was the non-pneumonic Legionnaires' disease (0.39 cases / 100,000 pop) with women being the main affected (0.42 cases / 100,000 pop). The territory with the highest incidence rate was Bolivar department (1.94 cases / 100,000 pop), followed by La Guajira (1.7 cases / 100,000 pop). Finally, age groups with the highest morbidity were 0-9.999 years old (1.16 cases / 100,000 pop) and system of identification for social subsidies beneficiaries (SISBEN) category with the highest number of total cases was level one (88 cases). According to these results, we can show that legionellosis in Colombia is more common than it could be thought. Nevertheless, cross-sectional and prospective studies should be conducted in our country in order to improve the knowledge of incidence, prevalence, and burden of disease.

Under the Weather: Legionellosis and Meteorological Factors.

The incidence of legionellosis, caused by the bacteria Legionella which are commonly found in the environment, has been increasing in New Jersey (NJ) over the last decade. The majority of cases are sporadic with no known source of exposure. Meteorological factors may be associated with increases in legionellosis. Time series and case-crossover study designs were used to evaluate associations of legionellosis and meteorological factors (temperature (daily minimum, maximum, and mean), precipitation, dew point, relative humidity, sea level pressure, wind speed (daily maximum and mean), gust, and visibility). Time series analyses of multi-factor models indicated increases in monthly relative humidity and precipitation were positively associated with monthly legionellosis rate, while maximum temperature and visibility were inversely associated. Case-crossover analyses of multi-factor models indicated increases in relative humidity occurring likely before incubation period was positively associated, while sea level pressure and visibility, also likely preceding incubation period, were inversely associated. It is possible that meteorological factors, such as wet, humid weather with low barometric pressure, allow proliferation of Legionella in natural environments, increasing the rate of legionellosis.

Screening-level microbial risk assessment of urban water locations: a tool for prioritization.

People in urban areas are exposed to microbial hazards in urban waters. In this study, various hazards, diseases, and water systems, where different recreation activities take place, are compared in an integrated quantitative microbial risk assessment (QMRA). The event and annual probability of gastrointestinal illness (GI) and Legionnaires'disease (LD) were analyzed in QMRA models using selected literature data. Highest mean event probabilities of GI were found for playing in pluvial flood from a combined sewer overflow (34%), swimming (18%), and rowing (13%) in the river, swimming (8.7%) and rowing (4.5%) in the lake, and playing in a water playground (3.7%) and in the pluvial flood from stormwater sewers (4.7%). At these locations, the GI probability was above the EU Bathing Water Directive threshold for excellent water quality (3%). All the annual risk medians were below the national incidence of legionellosis of 0.002%. The illness probability was most sensitive to the pathogens concentration (particularly Campylobacter, Norovirus, and Legionella) and exposure frequency. Therefore, site-specific pathogen data collection is the best next step to strengthen the certainty of the risk estimates. This study created an evidence-base that was used by water authorities to understand the health risks and set priorities for risk management.

Is Venice an ideal habitat for Legionella pneumophila?

Legionella bacterium manifests itself in Legionnaire's disease and Pontiac fever, it is mainly found and transmitted by aerosol produced in cooling towers, water distribution plants and medical equipment, and it affects mainly elder persons in poor health. The population of Venice Local Health Unit was divided in two areas of study and the incidence of legionellosis in residents of Venice historical centre (Distretto Sanitario 1) and in residents of the mainland and coastal areas (Distretti Sanitari 2, 3, 4) was calculated. The cases were those notified to the Public Health Unit by law, and the population of residents was that of the eligible for health care in the archives of the Local Health Unit. Only cases of legionellosis in residents who had not travelled in the 10 days previous of the onset of disease, and not related to nosocomial clusters were considered. The standardized incidence ratio was then calculated and confidence interval were defined by Poisson distribution. Given the population of the two areas, 59801 in Distretto Sanitario 1 and 237555 in Distretti 2, 3, 4, the raw incidence of disease is respectively 87 per 100000 and 20 per 100000 in time 2002-2010. The standardized incidence ratio for the population of Distretto Sanitario 1 vs the remaining population is 4.3. The difference in risk of getting the disease in this two residential areas geographically very close, is probably related to the different buildings' characteristics, old and difficult to maintain in Venice historical centre.

Seasonal Patterns of Legionellosis in Saitama, 2005^|^ndash;2009

Sporadic cases of legionellosis have increased in Saitama Prefecture. This study aimed to understand the characteristics and incidence of legionellosis in Saitama Prefecture by studying the corresponding data from Tokyo and all over Japan. We analyzed cases of legionellosis registered from 2005 through 2009 in the annual reports of the Infectious Disease Surveillance Center. There were two peaks in the incidence of legionellosis in Japan between June and November, and a trough between February and May every year. Similar seasonal characteristics were observed in both Tokyo and Saitama. Proper management of risk factors-such as cooling towers and other aerosol-generating devices, before and during the seasonal increase in these incidences-is essential as a prophylactic measure against legionellosis.

Legionellosis Outbreak Associated with Asphalt Paving Machine, Spain, 2009

From 1999 through 2005 in Alcoi, Spain, incidence of legionellosis was continually high. Over the next 4 years, incidence was lower, but an increase in July 2009 led health authorities to declare an epidemic outbreak. A molecular epidemiology investigation showed that the allelic profiles for all Legionella pneumophila samples from the 2009 outbreak patients were the same, thus pointing to a common genetic origin for their infections, and that they were identical to that of the organism that had caused the previous outbreaks. Spatial-temporal and sequence-based typing analyses indicated a milling machine used in street asphalt repaving and its water tank as the most likely sources. As opposed to other machines used for street cleaning, the responsible milling machine used water from a natural spring. When the operation of this machine was prohibited and cleaning measures were adopted, infections ceased.

Bathwater-Associated Cases of Legionellosis in Japan, with a Special Focus on &lt;i&gt;Legionella&lt;/i&gt; Concentrations in Water

To evaluate the relationship between the incidence of legionellosis and Legionella concentrations in bathwater, we sent a questionnaire to 76 prefectural and municipal public health laboratories in Japan and found that 35 had encountered cases of legionellosis and had implemented investigations to determine the sources of the infections. Based on the results of the questionnaire, we were able to analyze various characteristics of the patients, of the facilities that were thought to be associated with the cases, and of the species and serogroups of the isolates and concentrations of Legionella. Ninety-six cases were included in this study. The median age was 67 years (range, 13-89 years). The most prevalent underlying medical condition among patients was diabetes, and the second most prevalent was high blood pressure. Concentrations of Legionella in bathwater ranged from 10 to 160,000 CFU/100 ml. Ten episodes were selected in which causative strains were found in the suspected source environment, and were then confirmed by pulsed-field gel electrophoresis analysis, enabling us to provide an estimated infectious concentration range of Legionella of 90 to 140,000 CFU/100 ml. It was thus suggested that the current Japanese regulatory safety level for Legionella in bathwater, which is set below the detection limit of culture techniques (10 CFU/100 ml), should be appropriate to prevent bathwater-associated legionellosis. In tandem with the above-mentioned research, a review of literature concerning bathwater-associated legionellosis and typical cases was undertaken.

Increasing Incidence of Legionellosis in the United States, 1990–2005: Changing Epidemiologic Trends

An abrupt increase in the incidence of legionellosis in the United States has been noted since 2003. Whether the recent increase is associated with shifting epidemiologic trends has not been well characterized. We analyzed all cases of legionellosis reported to the Centers for Disease Control and Prevention through the National Notifiable Disease Surveillance System from 1990 through 2005. A total of 23,076 cases of legionellosis were reported to the Centers for Disease Control and Prevention from 1990 through 2005. The number of reported cases increased by 70% from 1310 cases in 2002 to 2223 cases in 2003, with a sustained increase to >2000 cases per year from 2003 through 2005. The eastern United States showed most of the increases in age-adjusted incidence rates after 2002, with the mean rate in the Middle Atlantic states during 2003-2005 exceeding that during 1990-2002 by 96%. During 2000-2005, legionellosis cases were most commonly reported in persons aged 45-64 years. Persons aged <65 years comprised 63% of total cases in 2000-2005. Age-adjusted incidence rates in males exceeded those in females for all age groups and years. Legionellosis incidence showed marked seasonality in eastern states, with most cases reported in the summer or fall. Reported legionellosis cases have increased substantially in recent years, particularly in the eastern United States and among middle-aged adults. Legionella infection should be considered in the differential diagnosis of any patient with pneumonia. Public health professionals should focus increased attention on detection and prevention of this important and increasing public health problem.

Editorial Commentary:Our Evolving Understanding of Legionellosis Epidemiology: Learning to Count

disease is also farther on the road to being cured when it breaks forth from concealment and manifests its power (Seneca, ca. 4 bc-65 ad) [1]. Legionella pneumophila burst onto the medical scene ~3 decades ago as the causative pathogen in a respiratory disease outbreak among American Legion conventioneers at Philadelphia's grand Bellevue Stratford Hotel [2]. As a result of the outbreak, 182 people became sick, 29 died, the hotel went out of business, and, ultimately, clinicians were introduced to a novel, virulent pathogen. The initial identification of legionellosis in the context of a large and virulent outbreak and the subsequent recognition of case clusters associated with cooling towers, fountains, and grocery store mist machines [3] did much to cement the perception of L pneumophila as an agent of respiratory outbreaks associated with inhalation of contaminated droplets. In the nosocomial field, such outbreaks have been associated with case-fatality rates exceeding 40% [4]. However, many clinicians now recognize that legionellosis is an important cause of sporadic community-acquired pneumonia and a relatively common cause of community-acquired pneumonia requiring admission to the intensive care unit [5]. As sensitive and noninvasive diagnostic options have expanded, so has the perceived spectrum of illness associated with Legionella species. A recent article by von Baum and colleagues [6] suggested that, when individuals with ambulatory communityacquired pneumonia are tested for legionellosis by urine antigen testing, nearly 4% may receive a diagnosis of legionellosis. Understanding of the links between the physical environment and legionellosis risk has undergone a parallel evolution. Legionella species are present in surface waters and ground water [7], and pathogenic species of Legionella frequently can be isolated from home and hospital waterdistribution systems, even in the presence of chlorine (and in the absence of identified outbreaks). The finding that monochloramination of potable water supplies (which is far more effective at killing Legionella species than is chlorination) is associated with a reduction in nosocomial legionellosis outbreaks [8] suggests that exposure to this uncommon pathogen via drinking water may actually be common. The association among advanced age, deficient immune status, and severe legionellosis likely results from a high frequency of microaspiration and the inability to clear aspirated organisms in individuals with these characteristics. In this issue of Clinical Infectious Diseases, Neil and Berkelman [9] provide a succinct and thought-provoking summary of recent trends in legionellosis in the United States. They report that the incidence of legionellosis increased markedly in the United States from 2002 through 2005. Should we be concerned that the incidence of a virulent infectious disease