Disadvantages of chronic disease templates in primary care consultations.
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Chronic Disease↗
Biomedical subjects
J N Eisenberg
Publications and source records attributed to J N Eisenberg.
An analysis of the Milwaukee cryptosporidiosis outbreak based on a dynamic model of the infection process.
We combined information on the temporal pattern of disease incidence for the 1993 cryptosporidiosis outbreak in Milwaukee with information on oocyst levels to obtain insight into the epidemic process. We constructed a dynamic process model of the epidemic with continuous population compartments using reasonable ranges for the possible distribution of the model parameters. We then explored which combinations of parameters were consistent with the observations. A poor fit of the March 1-22 portion of the time series suggested that a smaller outbreak occurred before the March 23 treatment failure, beginning sometime on or before March 1. This finding suggests that had surveillance systems detected the earlier outbreak, up to 85% of the cases might have been prevented. The same conclusion was obtained independent of the model by transforming the incidence time series data of Mac Kenzie et al. This transformation is based on a background monthly incidence rate for watery diarrhea in the Milwaukee area of 0.5%. Further analysis using the incidence data from the onset of the major outbreak, March 23, through the end of April, resulted in three inferred properties of the infection process: (1) the mean incubation period was likely to have been between 3 and 7 days; (2) there was a necessary concurrent increase in Cryptospordium oocyst influent concentration and a decrease in treatment efficiency of the water; and (3) the variability of the dose-response function in the model did not appreciably affect the simulated outbreaks.
Animals↗
Quantifying water pathogen risk in an epidemiological framework.
Traditionally, microbial risk assessors have used point estimates to evaluate the probability that an individual will become infected. We developed a quantitative approach that shifts the risk characterization perspective from point estimate to distributional estimate, and from individual to population. To this end, we first designed and implemented a dynamic model that tracks traditional epidemiological variables such as the number of susceptible, infected, diseased, and immune, and environmental variables such as pathogen density. Second, we used a simulation methodology that explicitly acknowledges the uncertainty and variability associated with the data. Specifically, the approach consists of assigning probability distributions to each parameter, sampling from these distributions for Monte Carlo simulations, and using a binary classification to assess the output of each simulation. A case study is presented that explores the uncertainties in assessing the risk of giardiasis when swimming in a recreational impoundment using reclaimed water. Using literature-based information to assign parameters ranges, our analysis demonstrated that the parameter describing the shedding of pathogens by infected swimmers was the factor that contributed most to the uncertainty in risk. The importance of other parameters was dependent on reducing the a priori range of this shedding parameter. By constraining the shedding parameter to its lower subrange, treatment efficiency was the parameter most important in predicting whether a simulation resulted in prevalences above or below non outbreak levels. Whereas parameters associated with human exposure were important when the shedding parameter was constrained to a higher subrange. This Monte Carlo simulation technique identified conditions in which outbreaks and/or nonoutbreaks are likely and identified the parameters that most contributed to the uncertainty associated with a risk prediction.
Animals↗
Warfarin therapy in primary care.
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Anticoagulants↗
The structural stability of a three-species food chain model.
A three-species food-chain model which was previously shown to exhibit chaotic dynamics was revisited. By exploring the sensitivity of that result this study found that complex behavior depended on the functional form chosen to model the interaction between the two highest species in the food chain. Two separate scenarios were explored: the gradual addition of refugia modeling the escape from predation at low prey densities; and the gradual addition of predator interference modeling territorial behavior. The addition of even a small amount of refugia provided a stabilizing influence as the chaotic dynamics collapsed to stable limit cycles. The results of adding interference to the model were more complex. Although the numerical simulations indicated that a low level of interference provided a stabilizing influence, the analytical results suggest that complex dynamics are possible for a range of parameter values that are biologically relevant. The sensitivity of the stability profile to functional changes in the model suggests two important ecological motivations for structural stability analysis. First, in ecological systems, environmental fluctuations cause continuous changes in the functional relationships between and within species, resulting in potential changes in the complexity of the dynamics over time. Second, slight changes in ecological structure may cause significant bifurcations; however, most ecological data are inadequate to distinguish such phenomena.
Animals↗
Dynamic model comparing the bionomics of two isolated Culex tarsalis (Diptera: Culicidae) populations: model development.
The population dynamics of Culex tarsalis in the Coachella and southern San Joaquin valleys of California were studied using Monte Carlo simulations. Multiple years of abundance data were averaged to extract a generalized seasonal pattern for each site. These patterns were used to establish qualitative goodness-of-fit criteria to assess model output and to evaluate the importance of model parameters in simulating mosquito population trends. The parameters associated with the degree of temperature and density dependency on larval mortality were found to be important components in determining whether or not the output was classified as having passed or failed on the basis of our criteria, whereas autogeny and the heterogeneity of developmental time were found not to be important.
Animals↗
Dynamic model comparing the bionomics of two isolated Culex tarsalis (Diptera: Culicidae) populations: sensitivity analysis.
A simulation model described (Eisenberg et al. 1994a) was used to compare the population dynamics of Culex tarsalis Coquillett in the Coachella and southern portion of the San Joaquin Valleys of California. Model outputs were classified as a pass if they met criteria that defined typical seasonal abundance patterns established by CO2 and New Jersey light trap data. The sensitivity of this classification to the model parameters was assessed by running multiple simulations for each valley site. Parameter sets associated with a pass were first analyzed separately for each valley and then compared. The two study sites were distinguished by the distributional characteristics of two parameters associated with temperature dependency. One of these parameters described the temperature dependence of larval mortality and the other the temperature dependence of adult egg development. We hypothesize that these isolated Cx. tarsalis populations evolved separately to maximize survival in their respective temperature regimes by adapting to different optimal larval survival temperatures and egg-development rates.
Analysis of Variance↗
System issues for Controlled Ecological Life Support Systems.
There are several characteristics of a Controlled Ecological Life Support System that are distinct from commonly engineered systems. These are: 1) the uncertainty, due to limited data availability, and variability due to the heterogeneity of biological subsystems; 2) the closed, ecological nature of the system; and 3) the primary criterion of maximizing the probability of survival. Consequences of these features include: complex dynamics characterized by time scales ranging from milliseconds to months, posing difficult problems with respect to mathematical modeling and predictability; and the necessity for a unique controller design that can translate the high level requirement of survivability to low-level actuator tasks. Future research in the systems and control area should include an ecological perspective focusing on the unique dynamical characteristics of a Controlled Ecological Life Support System.
Ecological Systems, Closed↗
Plasma MB creatine kinase in soccer players.
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Creatine Kinase↗
Probable adverse interaction between oral metoprolol and verapamil.
A combination of an oral beta-adrenergic blocking agent and verapamil has been advocated as a safe treatment for angina. A case of Wenckebach type atrioventricular block occurring in a patient on metoprolol and verapamil is reported. It is suggested that this combination is used with caution.
Angina Pectoris↗
The Serologic response to Cryptosporidium in HIV-infected persons: implications for epidemiologic research.
Advances in serologic assays for Cryptosporidium parvum have made serology an attractive surveillance tool. The sensitivity, specificity, and predictive value of these new assays for surveillance of immunocompromised populations, however, have not been reported. Using stored serum specimens collected for the San Francisco Men's Health Study, we conducted a case-control study with 11 clinically confirmed cases of cryptosporidiosis. Based on assays using a 27-kDa antigen (CP23), the serum specimens from cases had a median response immunoglobulin (Ig) G level following clinical diagnosis (1,334) and a net response (433, change in IgG level from baseline) that were significantly higher than their respective control values (329 and -32, Wilcoxon p value = 0.01). Receiver operator curves estimated a cutoff of 625 U as the optimal sensitivity (0.86 [0.37, 1.0]) and specificity (0.86 [0.37, 1.0]) for predicting Cryptosporidium infection. These data suggest that the enzyme-linked immunosorbent assay technique can be an effective epidemiologic tool to monitor Cryptosporidium infection in immunocompromised populations.
AIDS-Related Opportunistic Infections↗