Using SWAT, Bacteroidales microbial source tracking markers, and fecal indicator bacteria to predict waterborne pathogen occurrence in an agricultural watershed

Developing the capability to predict pathogens in surface water is important for reducing the risk that such organisms pose to human health. In this study, three primary data source scenarios (measured stream flow and water quality, modelled stream flow and water quality, and host-associated Bacteroidales) are investigated within a Classification and Regression Tree Analysis (CART) framework for classifying pathogen (Escherichia coli 0157:H7, Salmonella, Campylobacter, Cryptosporidium, and Giardia) presence and absence (P/A) for a 178 km(2) agricultural watershed. To provide modelled data, a Soil Water Assessment Tool (SWAT) model was developed to predict stream flow, total suspended solids (TSS), total N and total P, and fecal indicator bacteria loads; however, the model was only successful for flow and total N and total P simulations, and did not accurately simulate TSS and indicator bacteria transport. Also, the SWAT model was not sensitive to an observed reduction in the cattle population within the watershed that may have resulted in significant reduction in E. coli concentrations and Salmonella detections. Results show that when combined with air temperature and precipitation, SWAT modelled stream flow and total P concentrations were useful for classifying pathogen P/A using CART methodology. From a suite of host-associated Bacteroidales markers used as independent variables in CART analysis, the ruminant marker was found to be the best initial classifier of pathogen P/A. Of the measured sources of independent variables, air temperature, precipitation, stream flow, and total P were found to be the most important variables for classifying pathogen P/A. Results indicate a close relationship between cattle pollution and pathogen occurrence in this watershed, and an especially strong link between the cattle population and Salmonella detections.

A Canadian application of one health: integration of Salmonella data from various Canadian surveillance programs (2005-2010)

Most bacterial pathogens associated with human enteric illness have zoonotic origins and can be transmitted directly from animals to people or indirectly through food and water. This multitude of potential exposure routes and sources makes the epidemiology of these infectious agents complex. To better understand these illnesses and identify solutions to reduce human disease, an integrative approach like One Health is needed. This article considers the issue of Salmonella in Canada and interprets data collected by several Canadian surveillance and research programs. We describe recovery of Salmonella from various samples collected along the exposure pathway and compare the serovars detected in the different components under surveillance (animal, food, environment, and human). We then present three examples to illustrate how an approach that interprets multiple sources of surveillance data together is able to address issues that transcend multiple departments and jurisdictions. First, differences observed in recovery of Salmonella from different cuts of fresh chicken collected by different programs emphasize the importance of considering the surveillance objectives and how they may influence the information that is generated. Second, the high number of Salmonella Enteritidis cases in Canada is used to illustrate the importance of ongoing, concurrent surveillance of human cases and exposure sources to information domestic control and prevention strategies. Finally, changing patterns in the occurrence of ceftiofur-resistant Salmonella Heidelberg in retail meats and humans demonstrates how integrated surveillance can identify an issue in an exposure source and link it to a trend in human disease. Taken together, surveillance models that encompass different scales can leverage infrastructure, costs, and benefits and generate a multidimensional picture that can better inform disease prevention and control programs.

Quantitative multi-year elucidation of fecal sources of waterborne pathogen contamination in the South Nation River basin using bacteroidales microbial source tracking markers

Over a seven-year period (2004-2010) 1095 water samples were obtained from the South Nation River basin at multiple watershed monitoring sites (Ontario, Canada). Real-time PCR using Bacteroidales specific markers was used to identify the origin (human (10% prevalence), ruminant (22%), pig (~2%), Canada goose (4%) and muskrat (7%)) of fecal pollution. In parallel, the distribution of fecal indicator bacteria and waterborne pathogens (Cryptosporidium oocysts, Giardia cysts, Escherichia coli O157:H7, Salmonella enterica and Campylobacter spp.) was evaluated. Associations between the detection of specific Bacteroidales markers and the presence of fecal indicator bacteria, pathogens, and distinct land use or environmental variables were evaluated. Linear correlations between Bacteroidales markers and fecal indicator bacteria were weak. However, mean marker densities, and the presence and absence of markers could be discriminated on the basis of threshold fecal indicator densities. The ruminant-specific Bacteroidales marker was the most frequently detected marker in water, consistent with the large number of dairy farms in the study area. Detection of the human or the ruminant markers were associated with a slightly higher risk of detecting S. enterica. Detection of the muskrat marker was related to more frequent Campylobacter spp. detections. Important positive associations between markers and pathogens were found among: i) total Bacteroidales and Cryptosporidium and Giardia, ii) ruminant marker and S. enterica, and iii) muskrat and Campylobacter spp.

Spatiotemporal analysis of Cryptosporidium species/genotypes and relationships with other zoonotic pathogens in surface water from mixed-use watersheds

Nearly 690 raw surface water samples were collected during a 6-year period from multiple watersheds in the South Nation River basin, Ontario, Canada. Cryptosporidium oocysts in water samples were enumerated, sequenced, and genotyped by detailed phylogenetic analysis. The resulting species and genotypes were assigned to broad, known host and human infection risk classes. Wildlife/unknown, livestock, avian, and human host classes occurred in 21, 13, 3, and <1% of sampled surface waters, respectively. Cryptosporidium andersoni was the most commonly detected livestock species, while muskrat I and II genotypes were the most dominant wildlife genotypes. The presence of Giardia spp., Salmonella spp., Campylobacter spp., and Escherichia coli O157:H7 was evaluated in all water samples. The greatest significant odds ratios (odds of pathogen presence when host class is present/odds of pathogen presence when host class is absent) for Giardia spp., Campylobacter spp., and Salmonella spp. in water were associated, respectively, with livestock (odds ratio of 3.1), avian (4.3), and livestock (9.3) host classes. Classification and regression tree analyses (CART) were used to group generalized host and human infection risk classes on the basis of a broad range of environmental and land use variables while tracking cooccurrence of zoonotic pathogens in these groupings. The occurrence of livestock-associated Cryptosporidium was most strongly related to agricultural water pollution in the fall (conditions also associated with elevated odds ratios of other zoonotic pathogens occurring in water in relation to all sampling conditions), whereas wildlife/unknown sources of Cryptosporidium were geospatially associated with smaller watercourses where urban/rural development was relatively lower. Conditions that support wildlife may not necessarily increase overall human infection risks associated with Cryptosporidium since most Cryptosporidium genotypes classed as wildlife in this study (e.g., muskrat I and II genotype) do not pose significant infection risks to humans. Consequently, from a human health perspective, land use practices in agricultural watersheds that create opportunities for wildlife to flourish should not be rejected solely on the basis of their potential to increase relative proportions of wildlife fecal contamination in surface water. The present study suggests that mitigating livestock fecal pollution in surface water in this region would likely reduce human infection risks associated with Cryptosporidium and other zoonotic pathogens.

Investigation of an Escherichia coli environmental benchmark for waterborne pathogens in agricultural watersheds in Canada

Canada's National Agri-Environmental Standards Initiative sought to develop an environmental benchmark for low-level waterborne pathogen occurrence in agricultural watersheds. A field study collected 902 water samples from 27 sites in four intensive agricultural watersheds across Canada from 2005 to 2007. Four of the sites were selected as reference sites away from livestock and human fecal pollution sources in each watershed. Water samples were analyzed for Campylobacter spp., Salmonella spp., Escherichia coli O157:H7, Cryptosporidium spp., Giardia spp., and the water quality indicator E. coli. The annual mean number of pathogen species was higher at agricultural sites (1.54 ± 0.07 species per water sample) than at reference sites (0.75 ± 0.14 species per water sample). The annual mean concentration of E. coli was also higher at agricultural sites (491 ± 96 colony-forming units [cfu] 100 mL(-1)) than at reference sites (53 ± 18 cfu 100 mL(-1)). The feasibility of adopting existing E. coli water quality guideline values as an environmental benchmark was assessed, but waterborne pathogens were detected at agricultural sites in 80% of water samples with low E. coli concentrations (<100 cfu 100 mL(-1)). Instead, an approach was developed based on using the natural background occurrence of pathogens at reference sites in agricultural watersheds to derive provisional environmental benchmarks for pathogens at agricultural sites. The environmental benchmarks that were derived were found to represent E. coli values lower than geometric mean values typically found in recreational water quality guidelines. Additional research is needed to investigate environmental benchmarks for waterborne pathogens within the context of the "One World, One Health" perspective for protecting human, domestic animal, and wildlife health.

Associations among pathogenic bacteria, parasites, and environmental and land use factors in multiple mixed-use watersheds

Over a five year period (2004-08), 1171 surface water samples were collected from up to 24 sampling locations representing a wide range of stream orders, in a river basin in eastern Ontario, Canada. Water was analyzed for Cryptosporidium oocysts and Giardia cyst densities, the presence of Salmonella enterica subspecies enterica, Campylobacter spp., Listeria monocytogenes, and Escherichia coli O157:H7. The study objective was to explore associations among pathogen densities/occurrence and objectively defined land use, weather, hydrologic, and water quality variables using CART (Classification and Regression Tree) and binary logistical regression techniques. E. coli O157:H7 detections were infrequent, but detections were related to upstream livestock pasture density; 20% of the detections were located where cattle have access to the watercourses. The ratio of detections:non-detections for Campylobacter spp. was relatively higher (>1) when mean air temperatures were 6% below mean study period temperature values (relatively cooler periods). Cooler water temperatures, which can promote bacteria survival and represent times when land applications of manure typically occur (spring and fall), may have promoted increased frequency of Campylobacter spp. Fifty-nine percent of all Salmonella spp. detections occurred when river discharge on a branch of the river system of Shreve stream order = 9550 was >83 percentile. Hydrological events that promote off farm/off field/in stream transport must manifest themselves in order for detection of Salmonella spp. to occur in surface water in this region. Fifty seven percent of L. monocytogenes detections occurred in spring, relative to other seasons. It was speculated that a combination of winter livestock housing, silage feeding during winter, and spring application of manure that accrued during winter, contributed to elevated occurrences of this pathogen in spring. Cryptosporidium and Giardia oocyst and cyst densities were, overall, positively associated with surface water discharge, and negatively associated with air/water temperature during spring-summer-fall. Yet, some of the highest Cryptosporidium oocyst densities were associated with low discharge conditions on smaller order streams, suggesting wildlife as a contributing fecal source. Fifty six percent of all detections of ≥ 2 bacteria pathogens (including Campylobacter spp., Salmonella spp., and E. coli O157:H7) in water was associated with lower water temperatures (<∼ 14 °C; primarily spring and fall) and when total rainfall the week prior to sampling was >∼ 27 mm (62 percentile). During higher water temperatures (>∼ 14 °C), a higher amount of weekly rainfall was necessary to promote detection of ≥ 2 pathogens (primarily summer; weekly rainfall ∼>42 mm (>77 percentile); 15% of all ≥ 2 detections). Less rainfall may have been necessary to mobilize pathogens from adjacent land, and/or in stream sediments, during cooler water conditions; as these are times when manures are applied to fields in the area, and soil water contents and water table depths are relatively higher. Season, stream order, turbidity, mean daily temperature, surface water discharge, cropland coverage, and nearest upstream distance to a barn and pasture were variables that were relatively strong and recurrent with regard to discriminating pathogen presence and absence, and parasite densities in surface water in the region.

Molecular subtypes of Campylobacter spp., Salmonella enterica, and Escherichia coli O157:H7 isolated from faecal and surface water samples in the Oldman River watershed, Alberta, Canada

Campylobacter spp., Salmonella enterica, and Escherichia coli O157:H7 isolated from 898 faecal, 43 sewage, and 342 surface water samples from the Oldman River were characterized using bacterial subtyping methods in order to investigate potential sources of contamination of the watershed. Among these pathogens, Campylobacter spp. were the most frequently isolated from faecal, sewage, and surface water samples (266/895, 11/43, and 91/342, respectively), followed by Salmonella (67/898, 8/43, and 29/342, respectively), and E. coli O157:H7 (16/898, 2/43, and 8/342, respectively). Salmonella Rubislaw was the most common serovar isolated from water. This serovar was also isolated from two wild bird species. Most other serovars isolated from water were either not isolated from animals or were isolated from multiple species. E. coli O157:H7 was predominantly isolated from cattle. The most common phage-types of this pathogen from cattle were also the most common among water isolates, and there were exact pulsed field gel electrophoresis and comparative genomic fingerprint matches between cattle, sewage, and water isolates. Campylobacters were commonly isolated from surface waters and faeces from most animal species. Restriction fragment length polymorphism of the Campylobacter flaA gene identified several location and host species-specific (cattle, goose, pig) fingerprints. Molecular subtyping of these bacterial pathogens shows considerable promise as a tool for determining the sources of faecal pollution of water.

A methods comparison for the isolation and detection of thermophilic Campylobacter in agricultural watersheds

Campylobacter species contribute to an enormous burden of enteric illnesses around the world. This study compared two different methods for detecting Campylobacter species in surface water samples from agricultural watersheds across Canada. One method was based on membrane filtration (MF) of 500 ml water samples followed by selective microaerophilic enrichment at 42 degrees C in Bolton broth, isolation of Campylobacter on CCDA, and subsequent identification confirmation by a PCR assay. The second method was based on centrifugation (CF) of 1000 ml water samples, followed by selective microaerophilic enrichment at 42 degrees C in Bolton broth, isolation of Campylobacter on Modified Karmali Agar, and subsequent identification confirmation by a different PCR assay. Overall comparison of the CF and MF methods indicated that both methods found Camylobacterjejuni to be the most commonly detected Campylobacter species in 699 water samples from four agricultural watersheds across Canada, and that C. jejuni frequency of occurrence was similar by both methods. However, the CF method detected significantly higher frequencies of Campylobactercoli (17%) and other Campylobacter species (13%) than the MF method (11% and 3%, respectively). It was frequently found that one method would detect Campylobacter in a water sample when the other method would not for a simultaneously collected, duplicate water sample. This study indicates that methods can have significantly different recovery efficiencies for Campylobacter species, and that caution is needed when comparing studies that report on the frequency of occurrence of waterborne Campylobacter at the genus level when different detection methods are used.

Seasonal relationships among indicator bacteria, pathogenic bacteria, Cryptosporidium oocysts, Giardia cysts, and hydrological indices for surface waters within an agricultural landscape

The South Nation River basin in eastern Ontario, Canada is characterized by mixed agriculture. Over 1600 water samples were collected on a bi-weekly basis from up to 24 discrete sampling sites on river tributaries of varying stream order within the river basin between 2004 and 2006. Water samples were analyzed for: densities of indicator bacteria (Escherichia coli, Clostridium perfringens, enterococci, total and fecal coliforms), the presence of pathogenic bacteria (Listeria monocytogenes, E. coli O157:H7, Salmonella spp., Campylobacter spp.), and densities of parasite Giardia cysts and Cryptosporidium oocysts. Relationships between indicator bacteria, pathogens, and parasite oocysts/cysts were overall weak, seasonally dependent, site specific, but primarily positive. However, L. monocytogenes was inversely related with indicator bacteria densities. Campylobacter, Salmonella, Giardia cysts and Cryptosporidium oocysts were most frequently detected in the fall. E. coli O157:H7 was detected at a very low frequency. Exploratory decision tree analyses found overall that E. coli densities were the most utilitarian classifiers of parasite/pathogen presence and absence, followed closely by fecal coliforms, and to a lesser extent enterococci and total coliforms. Indicator bacteria densities that classified pathogen presence and absence groupings, were all below 100 CFU per 100 mL(-1). Microorganism relationships with rainfall indices and tributary discharge variables were globally weak to modest, and generally inconsistent among season, site and microorganism. But, overall rainfall and discharge were primarily positively associated with indicator bacteria densities and pathogen detection. Instances where a pathogen was detected in the absence of a detectable bacterial indicator were extremely infrequent; thus, the fecal indicators were conservative surrogates for a variety of pathogenic microorganisms in this agricultural setting. The results from this study indicate that no one indicator or simple hydrological index is entirely suitable for all environmental systems and pathogens/parasites, even within a common geographic setting. These results place more firmly into context that robust prediction and/or indicator utility will require a more firm understanding of microorganism distribution in the landscape, the nature of host sources, and transport/environmental fate affinities among pathogens and indicators.

Nosocomial Legionella pneumophila serogroup 5 outbreak associated with persistent colonization of a hospital water system

An outbreak of infections caused by Legionella pneumophila serogroup 5 was detected in a university hospital, and nosocomial reservoirs of the legionella epidemic were examined. Clinical isolates from two patients who had been affected by the L. pneumophila serogroup 5 outbreak, and from another patient with a legionella infection caused by the same serogroup 3 years later, were compared to L. pneumophila serogroup 5 isolates from the hospital water supply by two molecular methods, amplified fragment length polymorphism (AFLP) analysis and random amplified polymorphic DNA analysis (RAPD). Genotyping confirmed the epidemiological linkage of the first two patients, and linked their infections with the hospital water supply. The third clinical strain, which was also linked to the hospital water, was very similar to the epidemic strain. Even though the water distribution system was sanitized (superheat and flush sanitation), the epidemic strain was shown to be persisting in the hospital water outlets several years after its initial discovery.

Microbial etiology of community-acquired pneumonia in the adult population of 4 municipalities in eastern Finland

To determine the etiology of community-acquired pneumonia in the adult population of a defined area, specific antibody responses in paired serum samples, levels of circulating pneumococcal immune complexes in serum samples, and pneumococcal antigen in urine were measured. Samples (304 paired serum samples and 300 acute urine samples) were obtained from 345 patients > or =15 years old with community-acquired, radiologically confirmed pneumonia, which comprised all cases in the population of 4 municipalities in eastern Finland during 1 year. Specific infecting organisms were identified in 183 patients (including 49 with mixed infection), as follows: Streptococcus pneumoniae, 125 patients; Haemophilus influenzae, 12; Moraxella catarrhalis, 8; chlamydiae, 37 (of which, Chlamydia pneumoniae, 30); Mycoplasma pneumoniae, 30; and virus species, 27. The proportion of patients with pneumococcal infections increased and of those with Mycoplasma infections decreased with age, but for each age group, the etiologic profile was similar among inpatients and among outpatients. S. pneumoniae was the most important etiologic agent. The annual incidence of pneumococcal pneumonia per 1000 inhabitants aged > or =60 years was 8.0.

Chlamydia pneumoniae is an important cause of community-acquired pneumonia in school-aged children: serological results of a prospective, population-based study

The aetiology of community-acquired pneumonia in childhood was studied in the total population of 8851 children in the area of 4 municipalities in eastern Finland. All cases of community-acquired pneumonia (n = 201) were registered during a surveillance period of 12 months between September 1, 1981 and August 31, 1982. The diagnosis of pneumonia was verified radiologically in all identified cases. The diagnosis of chlamydial infection was based on an antibody response measured by complement fixation (CF), by enzyme immunoassay (EIA; IgG or IgM) or by microimmunofluorescence (MIF; IgG or IgM), and the diagnosis of mycoplasmal infection on CF alone. In total, 29 cases of Chlamydia sp. infection were diagnosed; 20 were caused by Chlamydia pneumoniae. Thus, C. pneumoniae was an aetiological agent in 10%, of the 201 pneumonia cases: the proportion was 9% for children aged 5-9 y and 31% for those aged 10 y or more. In the study population, the total incidence of C. pneumoniae pneumonia was 2.3/1000/y. Mycoplasma pneumoniae serology (CF) was positive in 44 patients (22%); the total incidence of M. pneumoniae pneumonia was 5.0/1000/y. Serological evidence of both Chlamydiae and M. pneumoniae was detected in 9 (41%) patients. Our results indicate that C. pneumoniae is an important cause of community-acquired pneumonia in school-aged children. Diagnostic serological response to Chlamydia species or M. pneumoniae was found in 42% of pneumonia patients between 5 and 9 y of age and in 67% of patients aged 10 y or more. Thus, we suggest that macrolides should be considered as an empirical antimicrobial treatment for community-acquired pneumonia, especially in school-aged outpatients.

Etiology of childhood pneumonia: serologic results of a prospective, population-based study

BACKGROUND

To investigate the etiology of pediatric community-acquired pneumonia, we conducted a prospective, population-based study covering the total population <15 years of age (n = 8851) in 4 municipalities in eastern Finland.

MATERIALS AND METHODS

The number of patients was 201; chest radiographs were available for all cases and paired sera for serologic assays were available for >90% of cases. The methods included assays for antibody response to 3 pneumococcal antigens, specific pneumococcal immune complex assays and conventional antibody tests for mycoplasmal, chlamydial and viral infections.

RESULTS

Serologic evidence of specific microbial etiology was obtained in 133 (66%) of the pneumonia patients. Bacterial infection was diagnosed in 102 cases (51%) and viral infection in 51 cases (25%). Streptococcus pneumoniae was the most common agent (57 cases; 28%), followed by Mycoplasma pneumoniae (44; 22%), respiratory syncytial virus (43; 21%) and Chlamydia spp. (29; 14%). Haemophilus influenzae was identified in only 6% and Moraxella catarrhalis in only 3% of the children. More than one specific infection was found in 51 patients (25%). The proportion of pneumococcal cases varied from 24 to 36% by age. Mycoplasma infections were seen mostly in patients > or =5 years and Chlamydia infections in patients > or =10 years of age.

CONCLUSIONS

The results of our prospective, strictly population-based study confirm the importance of S. pneumoniae in the etiology of community-acquired pneumonia in children of all ages. M. pneumoniae and Chlamydia pneumoniae are important from the age of 5 years onwards.

Risk factors for community-acquired pneumonia in children: a population-based case-control study

Risk factors for community-acquired pneumonia were studied by collecting data from all pneumonia patients (n = 201) in a defined child population between 3 months and 15 years of age during a surveillance period of 12 months, and from randomly selected healthy controls under 15 years of age (n = 250) from the same area. A structured questionnaire was used, with 409 (176 patients and 233 controls) families responding in total. The chi-square test, and the univariate and multivariate logistic regression analyses were used. The confounding effects of gender, age and place of acquisition were standardized, and the possible interactions between these variables and each individual risk factor were calculated. In the risk factor analysis, the responders were classified into 2 age groups: under 5 years and 5-14 years of age. In children under 5 years of age the significant risk factors were a history of recurrent respiratory infections during the past year [odds ratio (OR) 5.5], a history of wheezing episodes (OR 5.3), and a history of otitis media and tympanocentesis before the age of 2 years (OR 3.6). In the older children, the significant risk factors were a history of recurrent respiratory infections during the previous year (OR 3.0), and a history of wheezing periods at any age (OR 2.1). To sum up, a susceptibility to respiratory infections was found to be significantly associated with community-acquired pneumonia, and no interactions with age, gender or place of acquisition were significant. This trend was reflected by a history of wheezing and that of acute otitis media.

Incidence of community-acquired pneumonia in the population of four municipalities in eastern Finland

Between September 1, 1981, and August 31, 1982, all patients with suspected or confirmed pneumonia among the 46,979 inhabitants of four municipalities in the province of Kuopio, Finland, were reported to a pneumonia register by their attending physicians. In addition, two study pathologists reported all cases of pneumonia found at autopsy, and two permanent registers were checked for retrospective identification of patients. Chest radiographs were obtained from 97% of all patients. The final diagnosis was based on radiologic or autopsy criteria. A total 546 patients (323 males and 223 females) had community-acquired pneumonia; of these, 37% were less than 15 years of age, and 31% were 60 years of age or older. Nineteen percent of the patients had defined chronic conditions, and 42% were admitted to hospital. The case fatality rate was 4%. The overall incidence of community-acquired pneumonia per 1,000 inhabitants per year was 11.6 (13.9 in males, 9.4 in females). The age-specific incidence per 1,000 inhabitants per year was as follows: age < 5 years, 36.0; age 5-14 years, 16.2; age 15-59 years, 6.0; age 60-74 years, 15.4; and age > or = 75 years, 34.2.

Outbreak of Mycoplasma pneumoniae infection among hospital personnel studied by a nucleic acid hybridization test

An outbreak of Mycoplasma pneumoniae (MP) infection occurred during the period March-May 1989 among the personnel of the Accident and Emergency Department of the Kuopio University Hospital, Kuopio, Finland. The index patient was a young male orderly, who fell ill with severe pneumonia. His tracheal mucus sample proved to be strongly positive for MP when tested by a commercial DNA-RNA hybridization test (Gen-Probe). After the index patient two additional staff members (an orderly and a nurse) fell ill with pneumonia and 66 others showed symptoms of upper respiratory infection or fever. The most frequent symptoms were a sore throat, a cough, rhinitis and headaches. All 97 employees of the department were tested for the presence of MP in April-May 1989 using throat swabs as test material. Forty-three (44%) were found to be positive for MP by the 'Gen-Probe' test. Eight (19%) of the MP positive staff were completely asymptomatic. The MP positive staff were retested about 3 weeks later, whereupon 40 (93%) had become negative. Most of the persons involved in this outbreak suffered only from mild respiratory symptoms, suggesting that MP outbreaks like the present one may easily pass unnoticed.

Significance of a terminal R wave in lead V1 of the electrocardiogram

A terminal r wave in Lead V1 lower than 0.6 mV. was studied in the ECGs of four groups: (1) 104 healthy children, (2) 207 healthy young adults, (3) 171 patients with no autopsy evidence of a cardiopulmonary disease, and (4) 1,078 autopsy patients with a cardiopulmonary disease. Cases with a complete right bundle branch block were excluded. A terminal r wave occurred in 2.9 per cent healthy children, 1.4 per cent of healthy young adults, 0.6 per cent of patients without and in 5.9 per cent of patients with autopsy evidence of a cardiopulmonary disease. The occurrence of a terminal r wave was most common in pulmonary patients (10 per cent). But it was also found in patients with an anterior or a posterior myocardial infarction and in some cases of left ventricular hypertrophy. In the autopsy series RVH occurred in 57 per cent of patients with a Qr pattern, in 30 per cent of patients with a terminal r wave higher than the initial one, and in none of the patients with a terminal r wave lower than the initial one. It is concluded that the height of the terminal r wave has clinical significance. A terminal r wave higher than the initial one in Lead V1 is associated with a cardiopulmonary disease in subjects over 30 years of age, while an r wave lower than the initial one seems to be an innocent finding.