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Accounting for two population turnarounds in nonmetropolitan America.

"The turnaround [in U.S. rural-to-urban migration] of the 1970s, the metropolitan resurgence of the 1980s, and the rural rebound of the 1990s [have been] described as three unanticipated changes in migration.... [This chapter] compares the magnitude of the three changes in net migration and contrasts the two nonmetropolitan turnarounds.... The results support a view of the 1970s turnaround as the outcome of long-term deconcentrating trends that were interrupted from the late 1970s to the late 1980s by circumstances that favored metropolitan areas. The return of nonmetropolitan territory to net in-migration in the 1990s appears to be due in part to favorable economic conditions that allow more people to act on preferences for smaller places."

Americas↗

Residential relocation and regional redistribution of the elderly in the USA and Germany.

"This paper reviews some of the principal differences and similarities in the migration and spatial redistribution behavior of the older populations of the USA and of Germany.... The paper is divided into three distinct parts. The paper first reviews actual and prospective redistribution of the older population, with regard to interregional shifts of population as well as to changes in concentration along an urban-rural continuum. Following these macroscopic elements, the paper then moves to a presentation of the results of two ex post facto surveys (one taken in the USA and the other in Germany) of recent older movers in order to compare the motivations expressed for the move and the present degree of satisfaction with it. The concluding section considers the implications of redistribution at both geographic levels and of mover satisfaction in light of political developments as they are presently unfolding in Europe."

Adult↗

Family and internal migration in Taiwan.

"In this paper we examine internal migration in Taiwan in the 1960s when rural economic conditions were volatile, the shift from agriculture to non-farm employment was gaining momentum, and the government's policy of industrialization through export was adopted. Migration is seen as one component of households' survival/adaptation strategy.... Our empirical analyses are consistent with our a priori theoretical expectations that household access to land, participation in the local wage labor force, and access to migrants' social networks directly influenced how families in Taiwan deployed migration as a household survival strategy."

Asia↗

The use of grid sampling methodology for rapid assessment of the distribution of bancroftian filariasis.

The recent World Health Assembly Resolution to eliminate lymphatic filariasis as a public health problem once more brings to the fore the need for reliable data for the effective planning of disease control programmes. Most countries do not have data on the distribution of lymphatic filariasis and are therefore not in the position to initiate control programmes based on sound baseline data. We tested in Ghana in 1998-99 a method for the Rapid Assessment of the Geographical Distribution of Bancroftian Filariasis (RAGFIL) that uses a spatial sampling grid with 50 km between sampled villages, rapid assessment surveys for filariasis prevalence in the sampled villages and spatial analysis to estimate the geographical distribution of filariasis throughout the study area. The prevalence contours obtained with the 50 x 50-km sampling grid were operationally similar to those obtained with a 25 x 25-km grid. The predicted prevalence was not statistically different from the sample survey prevalence in 57 independent villages and the 50 x 50-km grid appears adequate for rapid mapping of filariasis. For the purpose of filariasis mapping, the antigen test would seem a better diagnostic test than clinical examination for hydrocoele. We recommend that a regional approach to mapping be used because of the importance of cross-border foci as demonstrated by our findings from the north of Ghana. Application of the method will provide the minimal information required for effective planning of treatment programmes, and will facilitate estimation of the number of people to be treated. It will also help improve estimates of the number of people at risk and affected, and of the burden of disease due to lymphatic filariasis in Africa.

Adolescent↗

Inequalities in mortality and illness in Trent NHS Region.

BACKGROUND: The Department of Health is encouraging health authorities to improve health status by tackling health inequalities. We defined ward level spatial health variations in Trent National Health Service Region, England, investigated urban and rural inequalities, and examined the relationship with deprivation, to identify the extent of small area health inequalities and to establish whether a quantifiable difference exists between urban and rural health as affected by deprivation. METHOD: A small area ecological study design was adopted and ward level (n=591) standardized ratios were calculated (population aged <75, n=3,900,000) for specific causes of death and limiting long-term illness. A classification was devised to assess ward health inequalities according to an urban-rural dimension. Deprivation was measured using the Townsend Index and the relationship with mortality and illness was analysed using Pearson product moment correlation. RESULTS: Wide variations in mortality and illness were evident at ward level, being widest for accident mortality (standardized mortality range 0-508). Stroke mortality accounted for the largest proportion of wards with standardized mortality ratios over 125 (36.2 per cent). Relative deprivation correlated strongly with limiting long-term illness (r=0.82) and all-cause mortality (r=0.68) across Trent, and in both urban and rural environments. CONCLUSION: The study set health inequalities within a regional context for Trent as an initiative to coincide with the Government's proposed health strategy for the next few years. Wide health inequalities were evident in Trent and the association between deprivation and health was of a similar magnitude in urban and rural wards. This small area approach allows health authorities access to ward level information in order to inform key debate on tackling health inequalities and distributing resources in relation to need.

Adolescent↗

[Fertility preferences in Latin America: trends and differentials in seven countries].

The authors use Bongaarts's fertility preference measurement methodology to examine and compare changes in fertility preferences in Colombia, Costa Rica, the Dominican Republic, Ecuador, Jamaica, Peru, and Trinidad and Tobago over the period 1975-1989. "The trends of observed and desired fertility are examined at the national level and by level of education and rural-urban place of residence. The data used comes from fertility surveys....such as the World Fertility Survey (WFS) and the Demographic and Health Survey (DHS). The analysis suggests that the changes in fertility between the dates of the two surveys...are not due to changes in desired fertility, but mainly to differences in the degree to which fertility is controlled to coincide with desired levels.... Both the WFS and the DHS show that unwanted fertility was significant in all countries, specially in the lower socioeconomic strata." (SUMMARY IN ENG)

Americas↗

Environmental injustice and the Mississippi hog industry.

The recent growth and restructuring of the swine industry in the state of Mississippi has raised various environmental and socioeconomic concerns. We spatially examined the location and attributes of 67 industrial hog operations to determine if African American and low-income communities have a high prevalence of industrial hog operations located near their neighborhoods at the census block group level. We used spatial data and cross-classification analysis to compare the prevalence of industrial hog operations in neighborhoods that are primarily African American and low income with the prevalence in neighborhoods that are African American and affluent. We also used logistic regression to evaluate the relationship between the environmental justice variables and the location of the industrial hog operations. The block group characterization showed a high prevalence of hog operations in the four highest quintiles compared with the lowest quintile for percentage African American and percentage poverty. At increasing levels of percentage African Americans and percentage of persons in poverty, there are 2.4-3.6 times more operations compared with the referent group; additionally, scale adjustment to only the hog counties reduces this to 1.8-3.1 more operations compared with the referent group. The inequitable distribution of hog-confined agricultural feeding operations in these communities may have adverse environmental impacts associated with industrial hog production, such as increased health risks and quality of life degradation, as have occurred in other areas having similar facilities.

Black or African American↗

Population ageing, retirement policy and living conditions of the elderly in China.

The authors discuss economic and social aspects of the predicted rapid aging of China's population. They conclude that "its economic impact will depend on the outcome of the birth control campaign in rural areas...and on the pace of transition towards the nuclear family. In view of the very primitive nature of the retirement and health insurance systems, a rapid breakdown of family structures would constitute a major threat to the welfare of the elderly. Excepting certain middle- or upper-class pensioners in large cities, the standard of living of the elderly population remains very low and, due to the co-residence of generations, it is closely linked to trends in average income."

Adult↗

The effects of rainfall and evapotranspiration on the temporal dynamics of Anopheles gambiae s.s. and Anopheles arabiensis in a Kenyan village.

The population dynamics of the larval and adult life stages of the malaria vector Anopheles gambiae Giles were studied in Miwani, western Kenya, in relation to meteorological conditions. Larval density within a habitat, the number of larval habitats and sibling species composition were investigated as determinants of larval population dynamics. Female vector densities inside local houses and sibling species composition were investigated as determinants of adult population dynamics. Larval densities were estimated using a modified area-sampling method. Within the habitats, all instars showed a highly aggregated distribution, with the exception of second instars. A longitudinal study on the larval populations of A. gambiae s.l. in two different types of habitat (dirt track and ditch) was carried out, using a novel sampling procedure. A. gambiae s.s. and Anopheles arabiensis, the two sibling species occurring sympatrically in the study area, showed some spatial segregation between the two types of habitat. Rainfall was significantly correlated with the number of A. gambiae s.l. larval habitats during the first 6 weeks of study taking 1 week time lag into account, while over the entire 5-month study period correlations were less clear. With 1 week time lag, rainfall was also significantly correlated with the number of female A. gambiae s.l. collected from CDC-light traps in the study houses. Both larval and adult populations showed a significant increase in the proportion of A. gambiae s.s. within the mixed population of A. gambiae s.s. and A. arabiensis over time. Although not significantly correlated, the ratio of rainfall over precipitation/potential evapotranspiration (P/PE), indicative of the humidity conditions in the area, was probably the driving force of this increase.

Animals↗

Epidemiology of endemic Oropouche virus transmission in upper Amazonian Peru.

A cross-sectional serosurvey of a rural community near Iquitos, Peru was conducted to determine Oropouche (ORO) virus antibody prevalence and risk factors for human infection. Venous blood samples, and demographic, social, and risk factor data were obtained from people age five years of age and older who lived in the village of Santa Clara on the Nanay River, a tributary of the Amazon River. Sera were tested for ORO viral antibody by an ELISA. The specificity of viral antibody reactivity was determined by a standard plaque-reduction neutralization test. Interview data were analyzed by univariate and multiple logistic regression to determine which variables were statistically associated with previous ORO viral infection, as indicated by the presence of IgG antibody. Final models were evaluated based on log-likelihood and Wald chi-square. Clustering of seropositive residents within houses was analyzed by the method of Walter. Among 1,227 persons sampled, 33.7% (n=414) were positive for ORO viral IgG antibody. Overall, antibody prevalence was similar for males (33.9%) and females (33.6%), and increased significantly with age for both sexes to include more than half of persons more than 25 years of age. The length of residence in the village was positively associated with serologic status; persons who had moved to the village within the past 15 years were less likely to be seropositive than life-long residents of the same age. Antibody prevalence among immigrants who had lived in Santa Clara more than 15 years was similar to that in life-long residents. The activity most predictive of previous ORO viral infection was travel to forest communities and travel to Iquitos. No evidence of spatial heterogeneity in ORO virus antibody distribution was observed. Results suggested that endemic transmission of ORO virus in this region has been ongoing during many decades, and that people are at considerable risk of infection.

Adolescent↗

A spatially disaggregate analysis of road casualties in England.

Spatially disaggregate ward level data for England is used in an analysis of various area-wide factors on road casualties. Data on 8414 wards was input into a geographic information system that contained data on land use types, road characteristics and road casualties. Demographic data on area-wide deprivation (the index of multiple deprivation) for each ward was also included. Negative binomial count data models were used to analyze the associations between these factors with traffic fatalities, serious injuries and slight injuries. Results suggest that urbanized areas are associated with fewer casualties (especially fatalities) while areas of higher employment density are associated with more casualties. More deprived areas tend to have higher levels of casualties, though not of motorized casualties (except slight injuries). The effect of road characteristics are less significant but there are some positive associations with the density of "A" and "B" level roads.

Accidents, Traffic↗

Leishmania/HIV co-infections: epidemiology in Europe.

As the AIDS pandemic spreads to rural areas and human visceral leishmaniasis (VL) becomes more common in suburban areas, there is an ever greater degree of overlap between the geographical distributions of the two diseases and, in consequence, an increasing incidence of Leishmania/HIV co-infection. Cases of the co-infection have been reported from 35 countries around the world but most have been recorded in south-western Europe. There has been a total of 1911 cases detected in Spain, France, Italy and Portugal. The incidence of Leishmania/HIV co-infection is expected to continue increasing in eastern Africa but to fall in south-western Europe as increasing numbers of HIV-positives in the latter region are given the new, highly active, antiretroviral therapy (HAART). In 1998, a world-wide network of surveillance for the co-infection, which now includes 28 member institutions, was established by the World Health Organization (WHO) and the Joint United Nations Programme on HIV/AIDS (UNAIDS). In south-western Europe, the surveillance system is based on 16 institutions and is already well established. The systematic use of standardized and recently computerized case-report forms, a central international registry at the WHO's headquarters in Geneva, and the use of a geographical information system (GIS) for mapping and monitoring the co-infections have together improved the overall quality of the epidemiological data-gathering. All member institutions of the global network report to the WHO on an annual basis. The data collected are then analysed and periodically disseminated through international publications. The GIS allows the relevant epidemiological and demographic data-sets to be integrated and permits all detected cases of co-infection to be mapped down to locality level. The system also allows the spatial distribution of cases to be visualised and analysed and the geographical spread of the co-infection to be monitored over time. The risk posed by co-infected patients, as a source of Leishmania infection for the sandflies feeding on them, has recently been confirmed. The parasites and HIV may also be transmitted as the result of needle-sharing among intravenous-drug users.

AIDS-Related Opportunistic Infections↗

Spatial clustering of childhood leukaemia: summary results from the EUROCLUS project.

The interpretation of reports of clusters of childhood leukaemia is difficult, first because little is known about the causes of the disease, and second because there is insufficient information on whether cases show a generalized tendency to cluster geographically. The EUROCLUS project is a European collaborative study whose primary objective is to determine whether the residence locations of cases at diagnosis show a general tendency towards spatial clustering. The second objective is to interpret any patterns observed and, in particular, to see if clustering can be explained in terms of either infectious agents or environmental hazards as aetiological agents. The spatial distribution of 13351 cases of childhood leukaemia diagnosed in 17 countries between 1980 and 1989 has been analysed using the Potthoff-Whittinghill method. The overall results show statistically significant evidence of clustering of total childhood leukaemia within small census areas (P=0.03) but the magnitude of the clustering is small (extra-Poisson component of variance (%) = 1.7 with 90% confidence interval 0.2-3.1). The clustering is most marked in areas that have intermediate population density (150-499 persons km[-2]). It cannot be attributed to any specific age group at diagnosis or cell type and involves spatial aggregation of cases of different ages and cell types. The results indicate that intense clusters are a rare phenomenon that merit careful investigation, although aetiological insights are more likely to come from investigation of large numbers of cases. We present a method for detecting clustering that is simple and readily available to cancer registries and similar groups.

Adolescent↗

The use of spatial analysis in mapping the distribution of bancroftian filariasis in four West African countries.

The geographical distribution of human infection with Wuchereria bancrofti was investigated in four West African countries (Benin, Burkina Faso, Ghana and Togo), using a commercial immunochromatographic test for filarial antigen. Efforts were made to cover each health-system implementation unit and to ensure no sampling point was >50 km from another, but otherwise the 401 study communities were selected at random. The aim was to enable spatial analysis of the data, to provide a prediction of the overall spatial relationships of the infection. The results, which were subjected to an independent random validation in Burkina Faso and Ghana, revealed that prevalence in the adult population of some communities exceeded 70% and that, over large areas of Burkina Faso, community prevalences were between 30% and 50%. Most of Togo, southern Benin and much of southern Ghana appeared completely free of the infection. Although there were foci on the Ghanaian coast with prevalences of 10%-30%, such high prevalences did not extend into coastal Togo or costal Benin. The prevalence map produced should be useful in prioritizing areas for filariasis control, identifying potential overlap with ivermectin-distribution activities undertaken by onchocerciasis-control programmes, and enabling inter-country and sub-regional planning to be initiated. The results indicate that bancroftian filariasis is more widely distributed in arid areas of Burkina Faso than hitherto recognized and that the prevalences of infection have remained fairly stable for at least 30 years. The campaign to eliminate lymphatic filariasis as a public-health problem in Africa will require significantly more resources (human, financial, and logistic) than previously anticipated.

Adolescent↗

Strategies to improve immunization services in urban Africa.

The urban poor constitute a rapidly increasing proportion of the population in developing countries. Focusing attention on underserved urban slums and squatter settlements will contribute greatly to immunization programme goals, because these areas account for 30-50% of urban populations, usually provide low access to health services, carry a large burden of disease mortality, and act as sources of infection for the city and surrounding rural areas. Improvement of urban immunization programmes requires intersectorial collaboration, use of all opportunities to vaccinate eligible children and mothers, identification of low-coverage neighbourhoods and execution of extra activities in these neighbourhoods, and community mobilization to identify and refer persons for vaccination. Improved disease surveillance helps to identify high-risk populations and document programme impact. New developments in vaccines, such as the high-dose Edmonston-Zagreb vaccine, will allow changes in the immunization schedule that facilitate the control of specific diseases. Finally, operational research can assist managers to conduct urban situation assessments, evaluate programme performance at the "micro" level, and design and monitor interventions.

Africa↗

Geographical distribution and dramatic increases in incidences of malaria: consequences of the resettlement scheme in Gambela, SW Ethiopia.

The spatial distribution of malaria results from the interaction between vector, parasite, host, physical and human environments. This basic geographical approach provides an illustration of the geographical distribution of malaria in the world, particularly in the tropical regions. Due to the global climate change and population movements, it is predicted that malaria could have a greater impact on the non-immune or unprepared populations in the Northern Hemisphere in the coming decades. Presently, Sub-Saharan Africa (SSA) is the most adversely affected region in the world. Like any other SSA country, Ethiopia suffers from both epidemic (unstable) and endemic (stable) malaria in the high and lowland regions, respectively. Gambela is one of the areas with stable malaria in the humid tropical region of the country. This study is based on observations, unpublished data, interviews and discussions with settlers and officials in Gambela. It is found that a degree of diverse malaria prevalence is associated with altitudinal, temperature and rainfall variations. Owing to the settlement and land-use changes, unexpected rainfall patterns, temperature increase, unstable political system and poverty, malaria has gone beyond its geographical limits. As a result, the number of malaria affected people has increased in the last 12 years. It is suggested that proper physical and social planning, understanding the geography, entomology, epidemiology, behaviour and life-cycle of malaria parasite, cooperation between the policy-makers, malaria specialists, neighbouring countries and international communities are urgent, if malaria has to be controlled and eradicated.

Altitude↗

The area-wide epidemiology of bovine trypanosomosis and its impact on mixed farming in subhumid West Africa; a case study in Togo.

This paper reports on an area wide study of all major variables determining the expression of trypanosomosis in cattle in the subhumid eco-zone of West Africa, taking Togo as an example. To enable systematic area-wide sampling, the country was divided in 311 grid-squares of 0.125 x 0.125 sides. Cross-sectional surveys were then conducted to generate maps or digital layers on cattle density, herd structure, ownership and breed. These data layers, except for the breed data, were subjected to a cluster analysis in order to define spatial patterns in animal husbandry systems. This analysis revealed two main systems: one is oriented towards integration with crop-agriculture and a second towards investment in cattle. These two systems could be further characterised by incorporating breed data. Zebu cattle and their crossbreeds are more favoured in the second system. The breed distribution map shows the actual situation but also serves to predict the outcome of progressive crossbreeding. An area wide trypanosomosis survey allowed the production of prevalence maps for Trypanosoma congolense, T. vivax and the associated packed cell volume (PCV) values. A simple curvi-linear relationship was established between vector density and disease prevalence. The regression between disease prevalence and PCV for taurine and zebu plus crossbreeds separately, revealed that taurine cattle maintain a comparatively high PCV level particularly in high prevalence scenarios. The relationship between the average herd PCV and cattle density suggests that herd PCV value may provide a mirror for the number of animals not kept because of the prevailing risk. The regression between agricultural intensity and cattle density subsequently in areas with decreasing herd PCV values reveals that the level of integration of cattle in crop production decreases with a decreasing PCV. Thus, despite the presence of taurine animals in Togo, the omnipresence of tsetse in particular Glossina tachinoides, remains a major obstacle to cattle raising and indirectly mixed farming development and intensification. It is argued that only with the present type of wide scale, spatial studies it becomes possible to clarify all the major variables influencing the expression of trypanosomosis. Spatial epidemiological studies at a macro level may form the basis for area wide trypanosomosis control in West Africa.

Agriculture↗

Ethnic differentials in early childhood mortality in Nepal.

This paper investigates the association of early childhood mortality (between birth and second birthday) with ethnicity in Nepal, based on data from the 1976 Nepal Fertility Survey, which was part of the World Fertility Survey. The approach is through a series of hazard models, which incorporate ethnicity, year of birth, mother's illiteracy, father's illiteracy, rural-urban residence, region, sex, maternal age, survival of previous birth, previous birth interval, and breast-feeding as covariates. Ethnic differentials in early childhood mortality are not explained by the other socioeconomic and demographic covariates, except for a modest effect of illiteracy, but the remaining covariates explain a great deal of variability in early childhood mortality itself. Analysis using an improved specification of breast-feeding as an age-varying covariate indicates, on average, that breast-feeding, relative to not breast-feeding, reduces age-specific mortality risks during the first 2 years of life by 76%, a very large effect.

Adolescent↗