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J S Koopman

Publications and source records attributed to J S Koopman.

At least 55 records · Page 3Linked to original sources
PubMed1984

Statistical procedures for estimating the community probability of illness in family studies: rhinovirus and influenza.

A statistical method is presented for determining acquisition rates of illness from community sources of infection and for distinguishing among viruses which are associated with different epidemic seasons. The new method consists of a computationally simple procedure for estimating the community transmission parameter and the standard error of the estimator. This method, as well as a previously developed maximum likelihood procedure, is applied to illness data as a means for distinguishing among broad patterns of illness acquisition. The periods evaluated are the rhinovirus, influenza A and influenza B seasons in Tecumseh, Michigan, for the years 1976-1980. Tecumseh households are stratified into exposure groups depending on age-group composition. Estimates are found for the risk differences of illness acquired from the community for households with different age-group distributions. Analysis of the Tecumseh data reveals that members of households with children are more apt than members of households without children to acquire illness associated with rhinovirus, influenza A and influenza B from the community. Members of households with just preschool children (and adults) are more apt than members of households with just school children (and adults) to acquire illness associated with rhinovirus and influenza B from the community. In contrast, members of households with just preschool children (and adults) are just as likely as members of households with just school children (and adults) to acquire illnesses associated with influenza A from the community.

Adolescent↗
PubMed1984

Simulation studies of influenza epidemics: assessment of parameter estimation and sensitivity.

The influenza simulation model of Elveback et al is used to evaluate the accuracy of the maximum likelihood procedure of Longini et al for estimating the secondary attack rate in households. The sample population from the Tecumseh Respiratory Illness Study is mapped into the simulation model and simulations are carried out over a range of parameter values and conditions, some of which were derived from influenza seasons in Tecumseh and from the Seattle Flu Study for the years 1975-1980. The estimation procedure is found to be quite robust for parameter values preset within appropriate limits for influenza. However, a significant difference is found between the preset and estimated household contact parameter for epidemics of medium and high intensity when the preset value is zero. Incremental increases in the household contact parameter are shown to produce marked increases in the overall infection attack rate demonstrating that household spread is an important link in maintaining infection in other mixing groups such as schools, preschool groups and neighbourhood clusters of households.

Adolescent↗
PubMed1984

Patterns and etiology of diarrhea in three clinical settings.

Acute diarrhea of young children was studied from September 1978 to April 1981 to determine age and time patterns, clinical characteristics and microbial association in two pediatric practices and in a hospital population in southern Michigan. The practice population sizes were estimated so that rates of diarrhea could be determined. Care was sought for about 0.85 episodes per child in the first year of life and 0.4 episodes in the second year of life. Bacterial pathogens were rarely identified in the practices and were identified in only 5% of hospitalized patients. Rotavirus was identified in 16% of the episodes in children under two years of age in the practices. These rotavirus diarrheas occurred mainly in the winter and were clearly more severe than nonrotavirus diarrheas. The rotavirus-infected patients did not, however, have more frequent respiratory symptoms. Respiratory symptom frequency was related to practice setting and income but not etiology. In the fall, before the rotavirus seasonal peak, a peak of nonrotaviral, nonbacterial diarrhea was seen in the practices. The symptoms were mild and a corresponding peak was not seen in hospital patients. The total direct costs of diarrheal illness to society were estimated to be due more to hospitalization than to outpatient care.

Adolescent↗
PubMed1984

Milk fat and gastrointestinal illness.

The population of a pediatric practice was followed prospectively and determinants of acute gastrointestinal illness were evaluated in a nested age-matched case-control study. Children over age one taking low fat milk as their only milk source in the three weeks prior to illness had five times the risk of a doctor's visit for acute gastrointestinal illness as did children taking only whole milk during the same time period. This increased risk could not be explained by numerous potentially confounding variables or potential biases. There was no indication that the increased risk differed for rotavirus positive or rotavirus negative illness, or that it varied by children's age.

Animals↗
PubMed1983

The Tecumseh study. XII. Enteric agents in the community, 1976-1981.

Enteric illnesses in residents of Tecumseh, Michigan, were studied from 1976 to 1981. The frequency of illness among adults and children increased each year in the late autumn, usually in November. This peak of illness preceded the main period of appearance of the rotaviruses, which were less regularly associated with another peak of illness. Rotaviruses were identified in 3.8% of all stool specimens collected; in specimens from children under two years of age, the annual rate of rotavirus identification was 10.4%. All rotaviruses were identified during the period from late December to early April. Bacterial pathogens were isolated from 3.3% of stool specimens, with no concentration in any age group or season. However, most enteric illnesses in the community were not associated with recognized pathogens. Testing of blood specimens collected in 1976-1978 by complement fixation confirmed the seasonal pattern of rotavirus activity. Rotavirus infections were documented in all age groups, even in older adults, and were associated with symptomatic illness.

Adenoviruses, Human↗
PubMed1982

Norwalk virus enteric illness acquired by swimming exposure.

In an epidemic of gastrointestinal illness strongly associated with swimming at a recreational park in Macomb County, Michigan, in July, 1979, the authors demonstrated the value of serologic testing to detect Norwalk virus infection. Rises in antibody titer to Norwalk virus were noted in all 11 individuals tested. Electron microscopy on stools from 20 ill individuals revealed only one with Norwalk virus-like particles. This particle was shown by radioimmunoassay and immune electron microscopy not to be Norwalk virus and not to have stimulated detectable antibodies in this individual. These results not only indicate that electron microscopy is insensitive in detecting Norwalk virus, but that it has the potential to mislead. A low rate of respiratory symptoms was associated with gastrointestinal illness in this Norwalk virus outbreak. The route of exposure might have been important for this. The outbreak was also noteworthy in that, although there was evidence of familial clusters of resistance, a very high percentage of the population was proved to be susceptible to the Norwalk virus.

Adolescent↗
PubMed1982

Estimating household and community transmission parameters for influenza.

A maximum likelihood procedure is given for estimating household and community transmission parameters from observed influenza infection data. The estimator for the household transmission probability is an improvement over the classical secondary attack rate calculations because it factors out community-acquired infections from true secondary infections. The mathematical model used does not require the specification of infection onset times and, therefore, can be used with serologic data which detect asymptomatic infections. Infection data were derived by serology and virus isolation from the Tecumseh Respiratory Illness Study and the Seattle Flu Study for the years 1975-1979. Included were seasons of influenza B and influenza A subtypes H1N1 and H3N2. The transmission characteristics of influenza B and influenza A(H3N2) and A(H1N1) outbreaks during this period are compared. Influenza A(H1N1), A(H3N2) and influenza B are found to be in descending order both in terms of ease of spread in the household and intensity of the epidemic in the community. Children are found to be the main introducers of influenza into households. the degree of estimation error from the misclassification of infected and susceptible individuals is illustrated with a stochastic simulation model. This model simulates the expected number of detected infections at different levels of sensitivity and specificity for the serologic tests used. Other sources of estimation error, such as deviation from the model assumption of uniform community exposure and the possible presence of superspreaders, are also discussed.

Epidemiologic Methods↗
PubMed1982

Household and community transmission parameters from final distributions of infections in households.

A model is devised for the distribution of the total number of cases in households from a homogeneous community. In the model, community-acquired infection serves as a source of initial infection within households as well as of possible further cases. In addition, infected household members can infect others in the household. Maximum likelihood procedures for the model parameters are given. The model is fitted to symptom data on influenza and the common cold. Influenza seems to spread more easily in the community than within the household, while the opposite may be the case for the common cold. The model, which does not require specification of the time of onset of infection for individuals, can be fitted to serological data; this would provide a more accurate measure of household infection than the symptom data used.

Common Cold↗
PubMed1981

Interaction between discrete causes.

The interaction contrast of disease rates (ICDR), a measure of deviation from an additive model of no interaction, is shown always to be zero or slightly negative when the assumptions of no interaction in the sufficient-component discrete causes model hold. Since all physical sources of interaction which one might postulate between discrete causes imply a deviation from this model, the ICDR is a good parameter to screen for causal interaction. Specific models which deviate from the assumptions of no interaction in the sufficient-component discrete causes model should be sought when the ICDR differs from zero. An example of parameterizing interaction in one such model is presented. The additive model is inconsistent with the multiplicative when two causes are studied; negative or no interaction in the multiplicative model might represent positive interaction in the additive model. Use of the multiplicative model to screen for causal interactions could thus lead to inappropriate decisions regarding the need to seek causal explanations for interaction. Since positive interaction in the multiplicative model implies positive interaction in the additive, there will be no such inappropriate decisions when positive interaction is observed in the multiplicative model.

Diabetes Mellitus↗
PubMed1981

Food, sanitation, and the socioeconomic determinants of child growth in Colombia.

To describe the causes of growth failure in a developing country, we studied family food availability, anthropometric measurements of preschool children, and family and neighborhood socioeconomic conditions in a stratified random sample of Cali, Colombia families. The influences on preschool child growth of food availability, neighborhood socioeconomic conditions, and family socioeconomic conditions were separated statistically. Neither food availability nor other family factors were related directly to growth, but neighborhood factors did have a strong relationship to growth. Children decreased progressively from 97.5 percent of expected weight in the top one-sixth of neighborhoods we studied to 89 per cent in the botton one-sixth. Food availability, although not related to growth, was strongly related to family factors. The top one-sixth of families had 115 percent of FAO (Food and Agricultural Organization) protein allowances, while the bottom one-sixth had only 75 per cent. These finding are inconsistent with food availability or family factors being the prinicipal causes of growth retardation. They are consistent with neighborhood determined factors, possibly enteric infections, being the principal cause of growth retardation in preschool children in Cali.

Body Height↗
PubMed1980

The Tecumseh Study. XI. Occurrence of acute enteric illness in the community.

Occurrence of acute enteric illnesses was examined in Tecumseh, Michigan, during the period 1965-1971. Incidence of illness was highest under age 3 years, fell thereafter and rose again during the age group 20-29 years. Below age 3 years, frequency was higher in males than in females, but above that age the pattern was reversed. Overall, the incidence of illness was 1.2 per person year. Approximately 65 per cent of illnesses occurred in the autumn-winter, and the remainder in spring-summer. Activity restriction was observed in 52 per cent of illnesses. Respiratory symptoms were reported in 27 per cent of enteric illnesses. The enteric-respiratory illness complex, which appeared to be a distinct entity, was more severe than other illnesses in term of activity restriction, fever, physician consultation and duration. A portion of the respiratory illnesses associated with the isolation of certain respiratory agents was found to include distinct enteric symptoms.

Acute Disease↗
PubMed1979

The investigation of related cases for the control of diarrhea in cities in developing countries.

An example of how follow-up of related cases of diarrhea by epidemiologically-oriented health promoters can result in important public health measures is described. The follow-up of related cases involved a search for an outbreak in which a population with a high attack rate could be defined in order to increase the likelihood of a successful investigation by means of a cross-sectional retrospective study design. Then, through standard epidemiologic techniques, the risk factors to be studied were selected and a questionnaire was designed and executed. The results of this investigation demonstrate that greater meticulousness in pursuing epidemiologic principles is required for success in diarrhea outbreak investigations in developing countries than in developed countries despite the fact that controllable contaminations discoverable by these techniques are much more frequent in the former. In the present investigation it was found that flavored drinks packaged in plastic by a process assuming increasing importance in food distribution were causing diarrhea because of unhygienic manufacturing procedures. A concomitant bacteriologic study helped confirm the epidemiologic findings, and bacteriologic cultures at different points in the manufacturing process suggested a solution to the contamination problem found.

Child↗
PubMed1978

Diarrhea and school toilet hygiene in Cali, Colombia.

In a 4-week period in early 1976 in a poor, working class area of Cali, Colombia, the prevalences of diarrhea, vomiting, common cold, and head lice in schoolchildren were measured in relation to classroom size and to the condition of the school toilets. The study found that unhygienic toilet conditions were related to diarrhea, and it was estimated that if all schools could reach the modest level of hygiene of the two schools with the relatively best facilities, diarrhea would be reduced by 44% and vomiting by 34%. Toilet hygiene was found to be unrelated to colds or head lice, which have similar social class distributions to diarrhea and vomiting. Crowding was found to be related to a small percentage of the prevalences of vomiting, head lice and colds.

Child↗