Recent trends in the epidemiology of non-typhoidal Salmonella in Israel, 1999-2009.

The aim of the present study was to assess the recent trends in the epidemiology of non-typhoid Salmonella in Israel using a sentinel laboratory-based surveillance network. Between 1999 and 2009, 8758 Salmonella stool isolates were reported by five sentinel laboratories. There was a significant decrease in the incidence rate of Salmonella isolates from 70·5/100,000 in 1999 to 21·6/100,000 in 2005 followed by a slight increase to 30·3/100,000 in 2009. Of all Salmonella, 64·3% were isolated from children in the 0-4 years age group. Up to 2008, S. Enteritidis was the most prevalent serotype and in 2009 S. Infantis emerged as the most common Salmonella serotype. The decrease in the incidence of S. Enteritidis and S. Typhimurium and increase in S. Infantis among humans were associated with a similar trend among breeding flocks, which followed significant preventive interventions conducted against S. Enteritidis and S. Typhimurium infections in poultry. Tight surveillance and education of food handlers and consumers should be enhanced to reduce the foodborne transmission of Salmonella in Israel.

Randomized, double-blind comparison of oral aprepitant alone compared with aprepitant and transdermal scopolamine for prevention of postoperative nausea and vomiting.

BACKGROUND: Aprepitant blocks the emetic effects of substance P. Scopolamine antagonizes muscarinic type 1 and histamine type 1 receptors. This study compares monotherapy and multimodal therapy by looking at complete response, nausea, vomiting, and rescue medication in patients at high risk for postoperative nausea and vomiting (PONV) treated with oral aprepitant with or without scopolamine. METHODS: We enrolled 120 patients in this randomized, double-blind trial. Inclusion criteria were: >18 yr old, ASA I-III, two or more Apfel four-point risk factors, undergoing an elective surgical procedure with a high risk of PONV expected to last at least 60 min. The primary outcome variable was complete response, that is, no emesis and no rescue therapy from 0 to 24 h. The outcomes measured included the incidences of nausea, vomiting, their composite, and the need for rescue medication. RESULTS: The aprepitant alone and aprepitant with scopolamine did not differ in complete responses (63% vs 57%, P=0.57) or net clinical benefit (26% vs 19%, P=0.38). The number who did not experience PONV and who used rescue medication did not differ. The incidence of PONV in the post-anaesthesia care unit did not differ nor did the use of rescue medications. CONCLUSIONS: This trial evaluating the effectiveness of aprepitant alone and in combination with scopolamine showed no difference between treatment groups. The primary objective, complete response, and secondary objectives, incidences of nausea, vomiting, their composite, and the need for rescue medication, all showed no statistical difference.

Excess mortality from seasonal influenza is negligible below the age of 50 in Israel: implications for vaccine policy.

PURPOSE: Evaluation of the severity of pandemic influenza requires reliable estimates of mortality attributable to the seasonal influenza. METHODS: Excess age-specific mortality during periods of influenza activity was evaluated in Israel during the period 1999-2006 for three death categories. For each respiratory year, the lowest monthly moving average for the mortality rate was subtracted from each month in the period of influenza activity. Average mortality rates in years with minimal influenza activity were deducted from corresponding months to exclude winter mortality unrelated to influenza. The sums of these results were used as estimates of excess mortality rates. RESULTS: Overall excess mortality rates ranged from 7.7 to 36.1 per 100,000 for all causes, and from 4.4 to 24.4 per 100,000 for respiratory and circulatory causes. Influenza was associated with an average of 869 (range 280-1,516) deaths annually from respiratory and circulatory diseases during seasons with significant influenza activity. About 90% of the influenza-associated mortality from respiratory and circulatory diseases was in the age group 65+ years and about 1% in the age group <50 years. The age group <50 years accounted for an annual average of seven deaths from respiratory and circulatory diseases. CONCLUSION: Annual mortality associated with seasonal influenza is highly variable. Under the age of 50 years, there is minimal seasonal influenza associated mortality. This information provides an important baseline for evaluating the severity of the A(H1N1) 2009 influenza pandemic, where persons under 50 years of age were often disproportionately represented.

A Middle East subregional laboratory-based surveillance network on foodborne diseases established by Jordan, Israel, and the Palestinian Authority.

In late 2002, health professionals from the ministries of health and academia of Jordan, the Palestinian Authority and Israel formed the Middle East Consortium on Infectious Disease Surveillance (MECIDS) to facilitate trans-border cooperation in response to infectious disease outbreaks. The first mission of MECIDS was to establish a regional, laboratory-based surveillance network on foodborne diseases. The development of harmonized methodologies and laboratory capacities, the establishment of a common platform of communication, data sharing and analysis and coordination of intervention steps when needed were agreed upon. Each of the three parties selected the microbiological laboratories that would form the network of sentinel laboratories and cover the different districts of each country and also designated one laboratory as the National Reference Laboratory (NRL). Data analysis units have been established to manage the data and serve as a central point of contact in each country. The MECIDS also selected a regional data analysis unit, the Cooperative Monitoring Centre (CMC) located in Amman, Jordan, and established a mechanism for sharing data from the national systems. Joint training courses were held on interventional epidemiology and laboratory technologies. Data collection started in July 2005 with surveillance of salmonellosis as the first target. This network of collaboration and communication established in an area of continuous dispute represents an important step towards assessing the burden of foodborne diseases in the region and is expected to be fundamental for coordination of public health interventions and prevention strategies.

Predictors for non-compliance of notified hepatitis C virus-positive blood donors with recommendation to seek medical counselling.

BACKGROUND: Notification of blood donors represents the commonest method of informing asymptomatic individuals of abnormal test results indicating exposure to hepatitis C virus (HCV) infection. Such notification is therefore important from both health and economic perspectives. This study aimed to identify predictors for non-compliance of HCV-positive blood donors with the National Blood Services recommendation to seek medical counselling. STUDY DESIGN AND METHODS: The current research is a cross-sectional study. Telephone interviews were conducted with 201 blood donors identified as HCV positive following blood donation during 2001-2002 (40% response rate). RESULTS: About 25% of all the notified blood donors did not seek any counselling; 29% (44/150) of those who requested medical advice from their primary care physicians (general practitoner's) were not referred to specialists. Age, alcohol consumption and non-practice of health-promoting behaviour were independent predictors of non-compliance with the blood services' recommendation. In particular, smoking (odds ratio, 2.0; 95% confidence interval 1.0-4.2) and not undergoing professional teeth cleaning (odds ratio 2.8; 95% confidence interval 1.3-6.1) were found to be significant predictors of non-compliance. CONCLUSION: The study provides essential data regarding the extent and risk factors for non-compliance of HCV-positive blood donors with recommendation to seek medical advice. Our results can assist in identifying blood donors who would not seek counselling, based on demographic factors and past exposure to risk factors for HCV. Improvements in the notification process and additional training of general practitoners regarding the management of HCV disease are needed.

Prevalence and correlates of diphtheria toxoid antibodies in children and adults in Israel.

A seroepidemiological study was performed to evaluate immunity to diphtheria and to determine the correlates of diphtheria toxoid antibody levels among children and adults in Israel. In total, 3,185 sera from an age-stratified sample of children and adults, obtained in 2000-2001, were tested for diphtheria toxoid antibodies by an in-house double-antigen ELISA. A level of or=0.1 IU/mL (full protection or seropositivity). Seronegativity increased significantly in subjects aged >50 years, reaching levels of 9.7%, 12.6% and 18.9% in the groups aged 50-54, 55-59 and >60 years, respectively (p 0.001), with rates of basic immunity following a similar pattern. Subjects born abroad had higher seronegativity rates than those born in Israel (7.7% vs. 4.9%; p 0.019). No difference in diphtheria toxoid antibody levels was found according to other demographical variables, such as gender, Jewish or Arab ethnicity, urban or rural settlements, and the subjects' place of residence. The level of immunity to diphtheria among children and adults in Israel was satisfactory, with the exception of individuals aged >50 years. The risk of diphtheria outbreaks is low, but sporadic cases may occur among individuals lacking basic immunity against the disease.

Canadian implantable defibrillator study (CIDS) : a randomized trial of the implantable cardioverter defibrillator against amiodarone.

BACKGROUND: Patients surviving ventricular fibrillation (VF) or sustained ventricular tachycardia (VT) are at a high risk of death due to a recurrence of arrhythmia. The implantable cardioverter defibrillator (ICD) terminates VT or VF, but it is not known whether this device prolongs life in these patients compared with medical therapy with amiodarone. METHODS AND RESULTS: A total of 659 patients with resuscitated VF or VT or with unmonitored syncope were randomly assigned to treatment with the ICD or with amiodarone. The primary outcome measure was all-cause mortality, and the secondary outcome was arrhythmic death. A total of 328 patients were randomized to receive an ICD. A thoracotomy was done in 33, no ICD was implanted in 18, and the rest had a nonthoracotomy ICD. All 331 patients randomized to amiodarone received it initially. At 5 years, 85.4% of patients assigned to amiodarone were still receiving it at a mean dose of 255 mg/day, 28.1% of ICD patients were also receiving amiodarone, and 21.4% of amiodarone patients had received an ICD. A nonsignificant reduction in the risk of death was observed with the ICD, from 10.2% per year to 8.3% per year (19.7% relative risk reduction; 95% confidence interval, -7.7% to 40%; P=0.142). A nonsignificant reduction in the risk of arrhythmic death was observed, from 4.5% per year to 3.0% per year (32.8% relative risk reduction; 95% confidence interval, -7.2% to 57.8%; P=0.094). CONCLUSIONS: A 20% relative risk reduction occurred in all-cause mortality and a 33% reduction occurred in arrhythmic mortality with ICD therapy compared with amiodarone; this reduction did not reach statistical significance.

Relationship between pacemaker dependency and the effect of pacing mode on cardiovascular outcomes.

BACKGROUND: A recently completed trial, the Canadian Trial of Physiological Pacing (CTOPP), showed that physiological pacing did not significantly reduce mortality, stroke, or heart failure hospitalization, but it did show that atrial fibrillation occurred less frequently in patients with physiological pacing. Many pacemaker patients experience only transient bradyarrhythmias with an adequate unpaced heart rate (UHR) and are not pacemaker-dependent. The purpose of the present analysis was to determine if pacemaker-dependent patients have an increased benefit from physiological pacing compared with non-pacemaker-dependent patients. METHODS AND RESULTS: Of 2568 patients included in the CTOPP trial, 2244 patients had a pacemaker dependency test performed at the first follow-up visit. The yearly event rate of cardiovascular death or stroke steadily increased with decreasing UHR in the ventricular pacing group, but it remained constant in the physiological pacing group. When the patients were subdivided to UHR 60 bpm, there was an interaction between pacing mode treatment and UHR subgroup. The Kaplan-Meier plot confirmed a physiological pacing advantage only in the UHR

Iodine-123 metaiodobenzylguanidine scintigraphic assessment of the transplanted human heart: evidence for late reinnervation.

OBJECTIVES: This study attempted to determine whether cardiac sympathetic reinnervation occurs late after orthotopic heart transplantation. BACKGROUND: Metaiodobenzylguanidine (MIBG) is taken up by myocardial sympathetic nerves. Iodine-123 (I-123) MIBG cardiac uptake reflects intact myocardial sympathetic innervation of the heart. Cardiac transplant recipients do not demonstrate I-123 MIBG cardiac uptake when studied < 6 months from transplantation. However, physiologic and biochemical studies suggest that sympathetic reinnervation of the heart can occur > 1 year after transplantation. METHODS: We performed serial cardiac I-123 MIBG imaging in 23 cardiac transplant recipients early (< or = 1 year) and late (> 1 year) after operation. In 16 subjects transmyocardial norepinephrine release was measured late after transplantation. RESULTS: No subject had visible I-123 MIBG uptake on imaging < 1 year after transplantation. However, 11 (48%) of 23 subjects developed visible cardiac I-123 MIBG uptake 1 to 2 years after transplantation. Only 3 (25%) of 12 subjects with a pretransplantation diagnosis of idiopathic cardiomyopathy demonstrated I-123 MIBG uptake compared with 8 (73%) of 11 with a pretransplantation diagnosis of ischemic or rheumatic heart disease (p = 0.04). All 10 subjects with a net myocardial release of norepinephrine had cardiac I-123 MIBG uptake; all 6 subjects without a net release of norepinephrine had no cardiac I-123 MIBG uptake. CONCLUSIONS: Sympathetic reinnervation of the transplanted human heart can occur > 1 year after operation, as assessed by I-123 MIBG imaging and the transmyocardial release of norepinephrine. Reinnervation is less likely to occur in patients with a pretransplantation diagnosis of idiopathic cardiomyopathy than in those with other etiologies of congestive heart failure.

Histopathological observations in the brains of children exposed to inhalational anesthetic agents: a retrospective autopsy-based study.

BACKGROUND: Numerous animal models have demonstrated neuronal damage resulting from anesthetic exposure in the developing brain. Studies have shown a relationship between anesthetic exposure and brain hypoxia, neurodegeneration and apoptosis. The relevance of data derived from controlled experimental studies to human neuropathology is a subject of debate. This study compares histopathological findings in post-mortem brain tissue specimens from children with and without exposure to inhalational anesthetic agents. METHODS: Autopsy reports were reviewed. Patients were divided into exposure and non-exposure groups defined as any procedure involving inhalational anesthetic agents. A retrospective chart review was performed collecting pathological findings of the brain. The autopsy results examined the presence of twelve different histopathological parameters reflecting morphologic changes in thirteen regions of interest in the central nervous system. RESULTS: Post-mortem neuropathological findings were analyzed. Thirteen different areas were focused upon and changes were categorized into twelve histopathological parameters. Gliosis, which was confirmed by immunohistochemical staining for glial fibrillary acidic protein, was more prevalent in the exposure group (N.=48) compared to the non-exposure group (N.=20) (P<0.05). CONCLUSION: The role of anesthetic neurotoxicity is not well understood. Numerous animal models have demonstrated neuronal apoptotic changes linked to anesthetic exposure, there is no tangible evidence supporting this relationship in humans. Our analysis demonstrates histopathological brain changes in children with anesthetic exposure not seen in the non-exposed group. Analysis was based on histopathological parameters representative of salient morphological findings of injury, which were encountered in anatomically divergent regions. Gliosis was the only statistically significant finding in post-mortem brain samples of patients who had received anesthetics.

Population group differences in trends in stroke mortality in Israel.

BACKGROUND AND PURPOSE: In Israel, stroke is the third most common cause of death. In 1997 stroke accounted for 2905 deaths (8.1% of total), 1390 of them among men (7.5% of total; crude mortality rate of 48.3/100 000) and 1515 among women (8.6% of total; crude rate of 51.7/100 000). This report presents trends on stroke mortality by population group and estimates of morbidity in Israel. METHODS: Data on stroke mortality in Israel during 1969-1997 were obtained from the Israel Central Bureau of Statistics. Age-specific and age-adjusted mortality rates were calculated for the 2 main population groups. Data on morbidity were obtained form the 1996/1997 National Health Survey. Hospitalization rates due to stroke are based on the national hospitalization data. RESULTS: A monotonic decrease in stroke mortality is evident in Jews during 1969-1997 in both sexes. Age-adjusted mortality rates declined by 62.5% for Jewish men and by 73.4% for Jewish women during 1969-1997. Among Arabs, there was a general decreasing trend in the mortality for both sexes during 1973-1997. The main difference in population group mortality trends was found in the group aged >/=75 years: a statistically significant decrease in mortality rates for Jews is evident, while no decrease is apparent for Arabs. On the basis of available data for 1990, an estimated 13 000 patients with stroke were hospitalized during 1997. CONCLUSIONS: During the last 25 years, age-adjusted stroke mortality in Israel has declined substantially, but the decline has been much greater among Jews than Arabs. The group aged >/=75 years shows the greatest difference in trends between Jews and Arabs. This finding may be explained by differences in risk factor distribution and case fatality rates.

Seasonal change in 24-hour blood pressure and heart rate is greater among smokers than nonsmokers.

In general, blood pressure is higher in winter than in summer, and this factor may be partly responsible for the higher mortality from cardiovascular disease in winter. Cigarette smoking causes an acute pressor response that may interact with this cardiovascular response to cold exposure. We sought to determine whether the seasonal variation in blood pressure and heart rate differs between cigarette smokers and nonsmokers. We evaluated 24-hour ambulatory systolic blood pressure (SBP), ambulatory diastolic blood pressure (DBP), and ambulatory heart rate of 97 healthy men (73 nonsmokers and 24 smokers), 28 to 63 years of age, during the summer and winter, taking indoor temperatures into consideration. Smokers and nonsmokers both had higher daytime ambulatory SBPs and DBPs in winter than in summer (after adjustment for potential confounders). However, the winter increase seen in the smokers was significantly higher for mean daytime SBP (7.3 versus 2.7 mm Hg, P<.01), for mean daytime DBP (4.4 versus 3.1 mm Hg, P=.051), and for ambulatory heart rate (3.9 versus -1.7 beats/min, P<.001). The double product increased from summer to winter (daytime) by 10.53 for smokers and by only 0.11 for nonsmokers (P<.01). There was an independent interaction between season and smoking status that affected SBP (standardized beta=0.66, P<.0001) and DBP (standardized beta=0.32, P<.0001). Smokers have a greater seasonal variation in blood pressure and heart rate than nonsmokers and show a larger increase in the cardiovascular load in winter. Smoking apparently potentiates the cardiovascular response to various climatic conditions. Season should be taken into account in studies of blood pressure and in the diagnosis and treatment of hypertension, particularly among cigarette smokers.

The Oregon brain aging study: neuropathology accompanying healthy aging in the oldest old.

OBJECTIVE: To describe the relationship between neuropathologic aging and longitudinal measures of cognitive function in healthy oldest old individuals. METHODS: Nondemented individuals without cardiovascular or other age-associated diseases of age > or =85 years were followed until death. Regional postmortem measures of senile plaque (SP) and neurofibrillary tangle (NFT) severity were examined in relationship to clinical status, cognitive measures, and rate of cognitive change. RESULTS: Among 19 healthy individuals, 10 became demented or had incipient dementia develop. Clinical status and rate of change in cognitive scores correlated with increasing brain lesion burden, particularly in neocortical regions. Compared to demented individuals, nondemented individuals had few or no neocortical NFT (p = 0.009) or SP (p = 0.001). There was a strong correlation between rate of cognitive change on Mini-Mental State Examination (MMSE) and neocortical NFT (r = 0.859, p = 0.001). The few NFT and SP in nondemented patients had a predilection for limbic areas. CONCLUSIONS: These results support a continuum in which AD is infrequent in the healthy, cognitively stable, oldest old. The minimal abnormalities in cognitively stable individuals are consistent with the notion that preclinical pathologic AD precedes obvious cognitive impairment. Longitudinal cognitive testing shows an increased burden of neuropathologic changes in those who have cognitive decline but are not functionally impaired and do not meet criteria for the diagnosis of dementia. The strong relationship between cumulative pathologic changes and rate of cognitive decline suggests that these lesions may have clinical consequences at any age and are not likely to be benign senescent changes.

Scintigraphic assessment of MIBG uptake in globally denervated human and canine hearts--implications for clinical studies.

To further characterize the behavior of metaiodobenzylguanidine (MIBG) in the myocardium and to test the hypothesis that the denervated heart would show normal early uptake on MIBG due to non-neuronal localization, we examined the early and late distribution of 123I-labeled MIBG in normal and globally denervated canine and human hearts. Canine hearts were denervated by intravenous injections of 6-hydroxydopamine, while patients were studied a mean of 4.3 mo following cardiac transplantation. Results in denervated hearts were compared to normal controls. Normal hearts showed prominent MIBG uptake on initial 5-min and 3-hr delayed images. Globally denervated canine hearts showed prominent uptake on initial images and absence of localization on delayed images, indicating complete washout of non-neuronally bound radionuclide. The transplanted human hearts showed no localization of MIBG on either early or delayed images. These results suggest that the non-neuronal uptake mechanism (uptake 2) is not significant in human myocardium. This finding has significant implications for interpreting the myocardial behavior of MIBG in various pathologic situations such as dilated cardiomyopathy.

Safety and feasibility of same day discharge in patients undergoing radiofrequency catheter ablation.

We retrospectively analyzed outcomes of radiofrequency catheter ablation in patients who were discharged the same day and compared them with patients staying overnight. For most tachyarrhythmias, it is safe and feasible to discharge patients undergoing radiofrequency ablation on the same day.

Canadian Implantable Defibrillator Study (CIDS): study design and organization. CIDS Co-Investigators.

The Canadian Implantable Defibrillator Study (CIDS) is an on-going randomized multicenter clinical trial that compares implantable cardioverter-defibrillator (ICD) therapy against amiodarone in patients with prior cardiac arrest or hemodynamically unstable ventricular tachycardia. Eligible patients are equally randomized to receive or not receive an ICD as initial management. Those not receiving an ICD receive amiodarone. All patients are seen in follow-up every 6 months. The primary outcome event cluster is arrhythmic death or any other death occurring within 30 days of therapy initiation. Secondary outcomes are all-cause mortality and nonfatal occurrences of ventricular tachycardia or fibrillation. The goal of the study is to recruit 400 patients over 4 years. All patients will be followed to the end of the year. This will result in an 80% chance of detecting a reduction in arrhythmic death of 58% by ICD if such a difference in truth exists. Recruitment began in October 1990 and 184 patients have been enrolled to date.

A prospective study of the effects of changes in smoking habits on blood count, serum lipids and lipoproteins, body weight and blood pressure in occupationally active men. The Israeli CORDIS Study.

In cross-sectional studies, significant differences in cardiovascular disease risk factors have been observed between smokers and non-smokers. The aim of this study was to examine the effects of smoking initiation and cessation on these factors in a population-based prospective study. 987 male employees in Israeli industry underwent health screening in the CORDIS study and were re-examined an average of two and a half years later. We examined the associations between smoking initiation and cessation and changes in blood count, serum lipids and lipoproteins, body weight and blood pressure. After adjusting for potential confounders, smoking cessation was associated with significant decreases in leukocyte count, hemoglobin and hematocrit whereas smoking initiation resulted in increased leukocyte count. There were moderate, non-significant increases in both serum HDL cholesterol (HDL-C) and LDL-C, and a slight decrease in serum triglycerides. Blood pressure remained essentially unchanged, despite the fact that smoking cessation resulted in a significant weight increase and smoking initiation in a significant decline in weight. These findings demonstrate that changes in smoking habits result in fairly rapid changes in blood count and body weight, but have much smaller effects on serum lipids and blood pressure.

Gender differences in platelet count and its association with cigarette smoking in a large cohort in Israel.

Cigarette smoking has an effect on platelet function and aggregation although the sensitivity of platelet count in reflecting this phenomenon is not known. The association of platelet count with smoking habits was examined in a cohort of 5017 Israeli industrial workers aged 20-64 years. Males had a significantly lower age-adjusted mean platelet count than females (225,600 vs 247,800/microliters; p less than 0.001). Female smokers had lower platelet counts than non-smokers (231,000 for heavy vs 252,000 for never smokers) with a strong dose-response relationship (p less than 0.0001), whereas among males platelet count was slightly higher in smokers (224,000 for non-smokers vs 227,000 for heavy smokers; p = 0.243). The difference in platelet count between the sexes remained almost identical after controlling for smoking status and hematocrit. In multiple regression analysis, the negative association between smoking and platelet count in women remained highly significant (p less than 0.001) after controlling for ethnic origin, alcohol consumption, body mass, hematocrit, cholesterol and HDL-cholesterol, whereas for males the slight positive association was not significant. The reduced platelet count observed in males compared with females and in female smokers, suggests that platelet count may reflect sex differences in hemostasis and the effects of smoking on the hemostatic system. This may have implications for the mechanisms underlying the pathogenesis of ischemic heart disease and should be explored further.

The male predominance in the incidence of infectious diseases in children: a postulated explanation for disparities in the literature.

In children, a male predominance in the incidence of symptomatic disease has been reported for some infectious agents and not for others. Not only are the factors underlying these sex differences poorly understood, but it is also not clear why the differences are described only for selected infectious diseases. In this study of sex- and age-specific incidence of infectious diseases in children, a possible explanation for the inconsistencies in the literature was explored. The sex ratio in reported disease incidence in Israel during a period of about 20 years was examined for various viral and bacterial infections. In addition, an hypothetical mathematical model was developed which assumes increased susceptibility to infectious disease (such as in relative immune deficiency) in a proportion of males. In children aged under 4 years, a higher incidence among males was consistently observed for all diseases, and the sex ratio varied between 1.16 (95% confidence interval (CI): 1.13-1.18) for shigellosis to 1.98 (95% CI: 1.79-2.17) for viral meningitis. The highest ratios were associated with the diseases which tend to present asymptomatically most often, which is consistent with the predictions of the model. The male excess in symptomatic disease appears to be present for most infectious diseases and this should be taken into account in studies comparing observed disease incidence between groups with different sex ratios. The inconsistencies in reports on the excess male morbidity for infectious diseases may be due to variations in symptomatic to asymptomatic infection ratios.

PIP: An explanation is provided for the male predominance in incidence of infectious diseases in children. A theoretical and mathematical model for predicting sex ratios for different prevalences of increased susceptibility to infectious disease in males is presented. The theoretical model states that males are more likely to experience symptomatic disease due to an increased prevalence of a factor such as immune deficiency. Variables are the proportion infected, the ratio of symptomatic (clinical) to asymptomatic (subclinical) infections, and the prevalence of males with increased susceptibility to infectious disease. Data included incidence of viral hepatitis, shigellosis and salmonellosis between 1966-85 and viral meningitis between 1971-85 by age and sex for Israeli Jews and nonJews. Other data for shorter time periods included poliomyelitis (1958-62), measles (1976-85), and diphtheria (1958-70). Single years of age were used for those 0-4 years. In diseases where vaccination has reduced the case load, the male to female incidence ratio was estimated with incidence density computed for the whole time period. The results of the analysis showed that male incidence 5 years in all 3 bacterial and 4 viral diseases was higher. The incidence ratios showed an excess of 20-100% for infectious diseases. This consistent pattern is not apparent in the literature because sex differences may be difficult to detect among symptomatic diseases; i.e., measles. There is also a lower symptomatic to nonsymptomatic infection ratio and small sex incidence ratio for shigellosis, salmonellosis and viral hepatitis. Where the symptomatic to nonsymptomatic ratio is about 1:50 or 1:100, the male to female incidence ratio will be much higher at about 2:1 and more readily detected. The immunodeficiency prevalence among males as an explanation for the susceptibility of males for diseases was not supported by an excess frequency of 2-3% in overt symptoms, although it is still considered a viable hypothesis. It is suggested that the inconsistencies in reports on male predominance in infectious diseases may be an artifact of statistics showing variability in the proportion of symptomatic infectious diseases. The implications are that comparisons should be made between the sexes. The disease rates may be biased by different proportions of males in the study and placebo groups in vaccine testing. Sex differences and disease should be examined further.