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Biomedical subjects

Frank C Curriero

Publications and source records attributed to Frank C Curriero.

18 recordsLinked to original sources
PubMed2006

Quantitative assessment of viable Cryptosporidium parvum load in commercial oysters (Crassostrea virginica) in the Chesapeake Bay.

The epidemiological importance of increasing reports worldwide on Cryptosporidium contamination of oysters remains unknown in relation to foodborne cryptosporidiosis. Thirty market-size oysters (Crassostrea virginica), collected from each of 53 commercial harvesting sites in Chesapeake Bay, MD, were quantitatively tested in groups of six for Cryptosporidium sp. oocysts by immunofluorescent antibody (IFA). After IFA analysis, the samples were retrospectively retested for viable Cryptosporidium parvum oocysts by combined fluorescent in situ hybridization (FISH) and IFA. The mean cumulative numbers of Cryptosporidium sp. oocysts in six oysters (overall, 42.1+/-4.1) were significantly higher than in the numbers of viable C. parvum oocysts (overall, 28.0+/-2.9). Of 265 oyster groups, 221 (83.4%) contained viable C. parvum oocysts, and overall, from 10-32% (mean, 23%) of the total viable oocysts were identified in the hemolymph as distinct from gill washings. The amount of viable C. parvum oocysts was not related to oyster size or to the level of fecal coliforms at the sampling site. This study demonstrated that, although oysters are frequently contaminated with oocysts, the levels of viable oocysts may be too low to cause infection in healthy individuals. FISH assay for identification can be retrospectively applied to properly stored samples.

Animals↗
PubMed2006

Characterizing population dynamics of Aedes sollicitans (Diptera: Culicidae) using meteorological data.

Numerous studies have investigated the role of weather on insect species. For mosquitoes, these studies have yielded mixed results. Although it is clear that weather impacts mosquito population dynamics, these investigations have failed to accurately characterize their fluctuations. We use a novel graphical method to examine large numbers of meteorological aggregations of varying lengths and lags simultaneously to establish relationships between these summary variables and mosquito counts, to gain a better understanding of the weather effects. Poisson regression models were developed to characterize the population dynamics of Aedes sollicitans (Walker) by using meteorological data and a 34-yr set of daily mosquito count data. The models accurately characterize mosquito dynamics over time and space. The aggregated meteorological variables included in the model were lowest minimum tides between days 27 and 14 before trapping, total precipitation between days 22 and 9, total precipitation on day 1 and the day of trapping, cooling degree-days on day 0, average minimum relative humidity between days 28 and 9, lowest stream flow from day 11 to day 0, and lowest minimum temperature between days 28 and 13.

Aedes↗
PubMed2005

Geographic identification of high gonorrhea transmission areas in Baltimore, Maryland.

Geographic approaches to sexually transmitted infection (STI) research frequently seek to identify areas where outreach STI testing may most effectively interrupt continued transmission of STIs. Many of the studies are limited, however, in that they fail to control for racial/ethnic composition of the high prevalence areas. These studies thus may be merely identifying the broader sexual networks of the high morbidity population and not the high transmission networks within them. Cluster detection analysis may be an appropriate approach to identify critical STI disease transmission locations. This study determined whether statistically significant geographic clusters of high prevalence gonorrhea cases can be located after controlling for race/ethnicity. Using a spatial scan statistic, the authors analyzed reported cases of gonorrhea (n = 32,454) in Baltimore City, Maryland, from 1994 to 1999 geocoded to the primary address and aggregated to census block groups (n = 709). They adjusted for the underlying distribution of the population aged 15-39 years and percent African American per census block group. The results identified eight significant clusters of high STI prevalence areas, reinforcing the inference that risks for gonorrhea are associated with definable sociogeographic spaces. The areas identified may be critical to control STIs and may provide important direction for further study and targeted interventions.

Adolescent↗
PubMed2005

Cross correlation maps: a tool for visualizing and modeling time lagged associations.

It has long been recognized that arthropod populations fluctuate with changes in environmental conditions and these changes occur at various spatial and temporal scales. Empirical studies that have explored associations between vector abundance and the environment often considered meterological events as leading indicators with their effects traditionally restricted to single points in time, such as precipitation 12 days prior to trapping. Field experience, however, suggests that the duration of these environmental effects on vectors often extends over a range or interval of time. Such a scenario is not directly interpretable from cross correlation plots routinely employed to visualize and identify time lag associations. Cross correlation maps are introduced as a way to generalize cross correlation plots and to visualize the effects of environmental conditions over intervals of time. This graphical method is flexible and can include different characterizations of environmental effects, as well as interactions among environmental variables. A time series of daily trapped female Ochlerotatus sollicitans mosquitos and leading meterologic conditions were used for demonstration. Associations shown in cross correlation maps were consistent with the arthropod biology and trapping efficacy and were also stronger than those identified at single time points using cross correlation plots. Poisson regression models for vector abundance built using meterological variables with both single and interval based leading time lags were compared. The approach based on the leading meterological events allowed to extend over time intervals reproduced the Oc. sollicitans daily population dynamics better than the traditional approach.

Animals↗
PubMed2005

Influence of geographic location in modeling blood pesticide levels in a community surrounding a U.S. Environmental protection agency superfund site.

In this study we evaluated residential location as a potential determinant for exposure to organochlorine compounds. We investigated the geographic distribution characteristics of organochlorine levels in approximately 1,374 blood samples collected in 1974 from residents of a community with a potential organochlorine source. Street addresses of Washington County, Maryland, residents were obtained and geocoded in a geographic information system. We used multivariate linear regression models to characterize the blood organochlorine levels of these residents that had been analyzed as part of previous studies using both environmental- and individual-level covariates. This was done to evaluate if the geographic distribution of blood levels in participants was related to the environmental source in the community. Model inference was based on generalized least squares to account for residual spatial variation. A significant inverse relationship was found between blood dieldrin levels and residential distance from the potential source. For every mile of distance from the source, blood dieldrin levels decreased 1.6 ng/g in study participants (p-value = 0.042), adjusting for age, sex, education level, smoking status, and drinking water source. 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) levels in the blood did not change significantly based on residential distance from the source, taking the same covariates into account. However, these results are limited by the inability to account for several potential confounders. This study demonstrates that spatially distributed covariates may play an important role in individual exposure patterns. Spatial information may enable researchers to detect a potential exposure pattern that may not be revealed with only nonspatial variables.

Environmental Monitoring↗
PubMed2004

Expression of cytochromes P450 1A1 and 1B1 in human lung from smokers, non-smokers, and ex-smokers.

Cytochromes P450 1A1 and 1B1 are known to bioactivate procarcinogens such as polycyclic aromatic hydrocarbons (PAHs) found in cigarette smoke and are inducible via an Ah receptor-mediated mechanism. The aim of this study was to examine the levels of expression of CYP1A1 and CYP1B1 in samples of lung from smokers (n = 18), non-smokers (n = 7), and ex-smokers (n = 7). Using immunoglobulin preparations of highly specific polyclonal antibodies and immunoblot analysis of microsomes from lung tissues, we determined the specific content for CYP1A1 and CYP1B1. For CYP1A1, we found median expression levels of 15.5 pmol/mg microsomal protein in smokers, 6.0 pmol/mg microsomal protein in non-smokers, and 19.0 pmol/mg microsomal protein in ex-smokers. The difference in median expression levels of smokers and ex-smokers compared to non-smokers was statistically significant. For CYP1B1, we found median expression levels of 1.8 pmol/mg microsomal protein in smokers, 1.0 pmol/mg microsomal protein in non-smokers, and 4.4 pmol/mg microsomal protein in ex-smokers. The difference in median expression levels between ex-smokers and non-smokers was statistically significant. These results suggest that levels of expression of CYP1A1 and CYP1B1 protein in lung tissues from smokers and ex-smokers are quantitatively greater than in non-smokers. By immunohistochemical analysis, we demonstrated the expression of CYP1A1 and CYP1B1 in normal human alveolar type I and II cells, ciliated columnar epithelial cells lining bronchoalveolar airways, and alveolar macrophages. These results confirm that CYP1A1 is expressed in normal human lung, appears to be induced in smokers, and show interindividual variation; the similar characteristics of CYP1B1 are demonstrated.

Adolescent↗
PubMed2004

Defining core gonorrhea transmission utilizing spatial data.

Spatial distribution of repeat and singly occurring gonorrhea in Baltimore, Maryland, was examined to identify clusters of core transmitters. Gonorrhea reported between 2001 and 2002 was geocoded and mapped. Those with more than one gonorrhea infection separated by more than 14 days during the 2-year period were considered repeaters. Other cases were treated as isolated events. Six definitions of core transmission were examined by census tracts with the highest quintiles of 1) cases for 2001, 2) cases for 2002, 3) rates for 2001, 4) rates for 2002, 5) counts of repeaters over the 2-year period, and 6) proportion of total cases that were repeaters. Of the 6,108 gonorrhea cases analyzed, 9% were repeaters. Repeaters were more likely to be female and younger. Core areas identified by definitions based on overall disease burden agreed well with each other but had poor agreement with definitions based upon repeat infections. Repeaters clustered to a greater extent at smaller distances than did singly occurring gonorrhea cases. Repeat gonorrhea infections are prevalent in Baltimore and likely represent behavior consistent with core transmission. Census tracts of core transmission defined by geographic distribution of repeat infections may indicate foci of highest risk sexual behaviors and high transmission.

Adolescent↗
PubMed2004

Does parental involvement predict new sexually transmitted diseases in female adolescents?

BACKGROUND: African American female adolescents living in low-income urban areas are at increased risk for sexually transmitted diseases. OBJECTIVE: To determine if high levels of perceived parental supervision and communication were associated with reduced gonorrhea (GC) and chlamydia (CT) incidence in low-income, African American, sexually experienced female adolescents, aged 14 to 19 years, attending urban health clinics. DESIGN: A prospective cohort study was used to determine the predictive value for high levels of parental supervision and communication on GC and CT infection in 158 adolescent females. Multiple logistic regression analysis explored the association between incident infection and perceived parental supervision and perceived parental communication while controlling for relevant demographic and behavioral factors (age, religious involvement, school enrollment, a 2-parent household, having a main sex partner, and having concurrent sex partners). RESULTS: When adjusted for age and baseline GC and CT infection, high levels of perceived parental supervision were associated with reduced GC and CT incidence (adjusted odds ratio, 0.06; 95% confidence interval, 0.01-0.31). High levels of perceived parental communication were not associated with reduced GC and CT incidence (adjusted odds ratio, 0.55; 95% confidence interval, 0.21-1.42). CONCLUSIONS: The link between parental supervision and disease acquisition is particularly valuable because it provides evidence that parental supervision can result in lower sexually transmitted disease rates in urban high-prevalence populations. This is important for interventions designed to increase parental involvement as a strategy for promoting protective sexual behaviors in female adolescents because it indicates that increased parental involvement can also influence subsequent disease acquisition.

Adolescent↗
PubMed2004

The role of area-level influences on prostate cancer grade and stage at diagnosis.

BACKGROUND: This research explores area-level social influences on prostate cancer, to test whether area-level influences explain disparities in U.S. prostate cancer burden. METHODS: The authors geocoded 23,993 1992-1997 Maryland prostate cancer cases, and linked cases to 1990 census data. The authors examined the effect of 17 area-level social variables, measured at block group, tract, and county, modeling individual and multilevel predictors of later stage and higher tumor grade. RESULTS: Younger age, black race, higher grade or ungraded tumors, and earlier year of diagnosis were associated with later stage. Block group percentage of white-collar workers (O.R. = 0.93, 95% C.I. = 0.89, 0.98), and county resources (O.R. = 0.94, 95% C.I. = 0.89, 0.98), were protective of later stage. Older age, black race, and earlier year of diagnosis were associated with higher grade. Block group income was protective for white men (O.R. = 0.92, 95% C.I. = 0.87, 0.96), but for all men, county resources increased risk of higher grade (O.R. = 1.23, 95% C.I. = 1.16, 1.31). CONCLUSIONS: Social resources did not significantly reduce racial differences. Results suggest tumor biology is related to relative resources, with better outcomes associated with greater small-area wealth in low-resource counties, but stage at diagnosis is associated with absolute resources, with better outcomes associated with higher small-area social class in high-resource counties.

Adolescent↗
PubMed2004

Geostatistics and GIS: tools for characterizing environmental contamination.

Geostatistics is a set of statistical techniques used in the analysis of georeferenced data that can be applied to environmental contamination and remediation studies. In this study, the 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) contamination at a Superfund site in western Maryland is evaluated. Concern about the site and its future clean up has triggered interest within the community because residential development surrounds the area. Spatial statistical methods, of which geostatistics is a subset, are becoming increasingly popular, in part due to the availability of geographic information system (GIS) software in a variety of application packages. In this article, the joint use of ArcGIS software and the R statistical computing environment are demonstrated as an approach for comprehensive geostatistical analyses. The spatial regression method, kriging, is used to provide predictions of DDE levels at unsampled locations both within the site and the surrounding areas where residential development is ongoing.

Dichlorodiphenyl Dichloroethylene↗
PubMed2004

Risk perceptions, condom use, and sexually transmitted diseases among adolescent females according to social network position.

BACKGROUND AND OBJECTIVES: Adolescent females are frequently treated as a homogenous group but could differ on their sexually transmitted disease (STD) risk because of individual attitudes and exposure through sexual networks. GOAL: The goal of this study was to determine if risk perceptions, condom use, and STD prevalence differs within sexual networks. STUDY DESIGN: Three hundred three adolescent females participating in a longitudinal study of adolescent STD risk perceptions and condom use were categorized as "core," "bridge," and "periphery" in a sexual network according to their and their main sex partner's risk information. Regression analysis determined differences in risk perceptions by network location. RESULTS: We demonstrated an inverse relationship between STD risk perceptions and network location. Adolescents with higher risk perceptions were more likely to use condoms, irrespective of network location. CONCLUSION: Female adolescents are a heterogeneous group exhibiting different risk perceptions. Different intervention strategies for adolescents at higher risk could be necessary. Interventions designed to raise risk perceptions could be associated with condom use, even for those adolescents at greatest risk.

Adolescent↗
PubMed2002

Survival curve estimation with partial non-random exposure information.

The objective of this paper is to estimate survival curves for two different exposure groups when the exposure group is not known for all observations, and the data is subject to left truncation and right censoring. The situation we consider is when the probability that the exposure group is missing may depend on whether the observation is censored or uncensored, in which case the exposure is not missing at random. The problem was motivated by a study of Alzheimer's disease to estimate the distribution of ages at diagnosis for individuals with and without an apolipoprotein E4 allele (the exposure group). Genotyping for this risk factor was incomplete and performed more frequently on the cases of Alzheimer's disease (the uncensored observations) than the censored observations. The survival curves are estimated in discrete time using an EM algorithm. A bootstrapping procedure is proposed that guarantees each bootstrap sample has the same proportion of observations with missing exposure. A simulation is performed to evaluate the bias of the estimators and to investigate design and efficiency issues. The methods are applied to the Alzheimer's disease study.

Adult↗
PubMed2002

Exploratory spatial analysis of pilot fatality rates in general aviation crashes using geographic information systems.

Geographic information systems and exploratory spatial analysis were used to describe the geographic characteristics of pilot fatality rates in 1983-1998 general aviation crashes within the continental United States. The authors plotted crash sites on a digital map; rates were computed at regular grid intersections and then interpolated by using geographic information systems. A test for significance was performed by using Monte Carlo simulations. Further analysis compared low-, medium-, and high-rate areas in relation to pilot characteristics, aircraft type, and crash circumstance. Of the 14,051 general aviation crashes studied, 31% were fatal. Seventy-four geographic areas were categorized as having low fatality rates and 53 as having high fatality rates. High-fatality-rate areas tended to be mountainous, such as the Rocky Mountains and the Appalachian region, whereas low-rate areas were relatively flat, such as the Great Plains. Further analysis comparing low-, medium-, and high-fatality-rate areas revealed that crashes in high-fatality-rate areas were more likely than crashes in other areas to have occurred under instrument meteorologic conditions and to involve aircraft fire. This study demonstrates that geographic information systems are a valuable tool for injury prevention and aviation safety research.

Accidents, Aviation↗
PubMed2002

Temperature and mortality in 11 cities of the eastern United States.

Episodes of extremely hot or cold temperatures are associated with increased mortality. Time-series analyses show an association between temperature and mortality across a range of less extreme temperatures. In this paper, the authors describe the temperature-mortality association for 11 large eastern US cities in 1973-1994 by estimating the relative risks of mortality using log-linear regression analysis for time-series data and by exploring city characteristics associated with variations in this temperature-mortality relation. Current and recent days' temperatures were the weather components most strongly predictive of mortality, and mortality risk generally decreased as temperature increased from the coldest days to a certain threshold temperature, which varied by latitude, above which mortality risk increased as temperature increased. The authors also found a strong association of the temperature-mortality relation with latitude, with a greater effect of colder temperatures on mortality risk in more-southern cities and of warmer temperatures in more-northern cities. The percentage of households with air conditioners in the south and heaters in the north, which serve as indicators of socioeconomic status of the city population, also predicted weather-related mortality. The model developed in this analysis is potentially useful for projecting the consequences of climate-change scenarios and offering insights into susceptibility to the adverse effects of weather.

Climate↗
PubMed2002

Survival following a diagnosis of Alzheimer disease.

CONTEXT: Survival following a diagnosis of Alzheimer disease (AD) is important information for health planners, caregivers, patients, and their families. OBJECTIVES: To estimate the duration of survival following a diagnosis of AD and to determine the effect of AD on life span. DESIGN, SETTING, AND PARTICIPANTS: Follow-up of participants of the Baltimore Longitudinal Study of Aging who were older than 55 years (January 1, 1985-September 30, 1999). MAIN OUTCOME MEASURES: Survival duration. RESULTS: The median survival time following a diagnosis of AD depended strongly on the patient's age at diagnosis. The median survival times ranged from 8.3 years for persons diagnosed as having AD at age 65 years to 3.4 years for persons diagnosed as having AD at age 90 years. There were no significant differences between men and women in survival after having a diagnosis of AD. Diagnoses of AD at ages 65 and 90 years were associated with approximately a 67% and 39% reduction in median life span, respectively. CONCLUSIONS: The effect of a diagnosis of AD on life span depends crucially on the age of the person when AD is diagnosed. Caregivers, patients, and their families could plan on a median life span as long as 7 to 10 years for patients whose conditions are diagnosed when they are in their 60s and early 70s, to only about 3 years or less for patients whose conditions are diagnosed when they are in their 90s.

Age Factors↗
PubMed2002

Mixture models for quantitative HIV RNA data.

Clinical investigators are increasing their use of quantitative determinations of HIV viral load in their study populations. The distributions of these measures may be highly skewed, left-censored, and with an extra spike below the detection limit of the assay. We recommended use of a mixture model in this situation, with two sets of explanatory covariates. We extend this model to incorporate multiple measures across time, and to employ shared parameters as a way of increasing model efficiency and parsimony. Data from a cohort of HIV-infected men are used to illustrate these features, and simulations are performed to assess the utility of shared parameters.

Brazil↗
PubMed2002

Geographic patterns of pilot fatality rates in commuter and air taxi crashes.

BACKGROUND: Geographic information systems are widely used in studies of diseases. However, their value for aviation safety research has not been adequately explored. PURPOSE: This study examined the geographic patterns of pilot fatality rates in commuter and air taxi operations. METHODS: Crash data recorded by the National Transportation Safety Board under FAR Part 135 were used to create a digital map of all crash sites in the continental United States between 1983 and 1998. Fatality rates in crashes were calculated and then interpolated to create a contoured map of rates. A test of significance was performed using Monte Carlo simulations. High-, medium-, and low-rate areas were then compared for pilot characteristics, airplane characteristics, and crash circumstance. RESULTS: Of the 1094 commuter and air taxi crashes studied, 25% resulted in a pilot fatality. A large geographic area with a pilot fatality rate of > or = 36% extended through portions of Michigan, Indiana, and Illinois. A relatively low fatality rate (< 15%) prevailed over an area extending from Texas to northwest Georgia. Crashes in high-rate areas were significantly more likely than crashes elsewhere to have occurred at night and during instrument meteorological conditions. CONCLUSION: The geographic analysis revealed a distinctive pattern of pilot fatality rates from Part 135 crashes. Factors underlying the geographic pattern should be investigated, with particular attention to the great geographic variability of terrain and weather phenomena between the north and south regions of the United States.

Accidents, Aviation↗