Analytically Derived Neighborhoods in a Rapidly Growing West African City: The Case of Accra, Ghana.

Large numbers of people are currently migrating from the poor, inland areas of West Coast Africa to the major cities of Lagos, Accra, Abidjan, and other budding metropolises (Figures 1 and 2). The infrastructure of the Sub-Saharan African cities is inadequate to service their burgeoning populations. An argument is presented for using scientifically derived neighborhoods as the building blocks for current African urban understanding and planning.

Fine scale spatiotemporal clustering of dengue virus transmission in children and Aedes aegypti in rural Thai villages.

Background: Based on spatiotemporal clustering of human dengue virus (DENV) infections, transmission is thought to occur at fine spatiotemporal scales by horizontal transfer of virus between humans and mosquito vectors. To define the dimensions of local transmission and quantify the factors that support it, we examined relationships between infected humans and Aedes aegypti in Thai villages.

Methodology/principal Findings: Geographic cluster investigations of 100-meter radius were conducted around DENV-positive and DENV-negative febrile "index" cases (positive and negative clusters, respectively) from a longitudinal cohort study in rural Thailand.

Underrecognized mildly symptomatic viremic dengue virus infections in rural Thai schools and villages.

Background: The understanding of dengue virus (DENV) transmission dynamics and the clinical spectrum of infection are critical to informing surveillance and control measures. Geographic cluster studies can elucidate these features in greater detail than cohort studies alone.

Methods: A 4-year longitudinal cohort and geographic cluster study was undertaken in rural Thailand.

Connecting the Dots Between Health, Poverty and Place in Accra, Ghana.

West Africa has a rapidly growing population, an increasing fraction of which lives in urban informal settlements characterized by inadequate infrastructure and relatively high health risks. Little is known, however, about the spatial or health characteristics of cities in this region or about the spatial inequalities in health within them. In this article we show how we have been creating a data-rich field laboratory in Accra, Ghana, to connect the dots between health, poverty, and place in a large city in West Africa.

Epidemiology of dengue virus in Iquitos, Peru 1999 to 2005: interepidemic and epidemic patterns of transmission.

Background: Comprehensive, longitudinal field studies that monitor both disease and vector populations for dengue viruses are urgently needed as a pre-requisite for developing locally adaptable prevention programs or to appropriately test and license new vaccines.

Methodology And Principal Findings: We report the results from such a study spanning 5 years in the Amazonian city of Iquitos, Peru where DENV infection was monitored serologically among approximately 2,400 members of a neighborhood-based cohort and through school-based absenteeism surveillance for active febrile illness among a subset of this cohort. At baseline, 80% of the study population had DENV antibodies, seroprevalence increased with age, and significant geographic variation was observed, with neighborhood-specific age-adjusted rates ranging from 67.

Neighborhoods and Fertility in Accra, Ghana: An AMOEBA-based Approach.

Fertility levels remain high in most of sub-Saharan Africa, despite recent declines, and even in a large capital city such as Accra, Ghana, women are having children at a pace that is well above replacement level and this will contribute to significant levels of future population growth in the city. Our purpose in this paper is to evaluate the way in which neighborhood context may shape reproductive behavior in Accra. In the process, we introduce several important innovations to the understanding of intra-urban fertility levels in a sub-Saharan African city: (1) despite the near explosion of work on neighborhoods as a spatial unit of analysis, very little of this research has been conducted outside of the richer countries; (2) we characterize neighborhoods on the basis of local knowledge of what we call "vernacular neighborhoods"; (3) we then define what we call "organic neighborhoods" using a new clustering tool-the AMOEBA algorithm-to create these neighborhoods; and then (4) we evaluate and explain which of the neighborhood concepts has the largest measurable contextual effect on an individual woman's reproductive behavior.

Distance threshold for the effect of urban agriculture on elevated self-reported malaria prevalence in Accra, Ghana.

Irrigated urban agriculture (UA), which has helped alleviate poverty and increase food security in rapidly urbanizing sub-Saharan Africa, may inadvertently support malaria vectors. Previous studies have not identified a variable distance effect on malaria prevalence from UA. This study examines the relationships between self-reported malaria information for 3,164 women surveyed in Accra, Ghana, in 2003, and both household characteristics and proximity to sites of UA.

Spatial and temporal clustering of dengue virus transmission in Thai villages.

Background: Transmission of dengue viruses (DENV), the leading cause of arboviral disease worldwide, is known to vary through time and space, likely owing to a combination of factors related to the human host, virus, mosquito vector, and environment. An improved understanding of variation in transmission patterns is fundamental to conducting surveillance and implementing disease prevention strategies. To test the hypothesis that DENV transmission is spatially and temporally focal, we compared geographic and temporal characteristics within Thai villages where DENV are and are not being actively transmitted.

Spatial and temporal clustering of Kawasaki syndrome cases.

Background: The etiology of Kawasaki syndrome (KS) remains unknown despite 30 years of intensive search for an agent. Epidemiologic clues to a possible infectious etiology include the seasonal distribution of cases, the previous occurrence of epidemics, the clinical features of the syndrome that mimic other infectious rash/fever illnesses in children, the self-limited nature of the illness, and the peak age incidence in the toddler years.

Methods: We examined the epidemiology and spatial and temporal distribution of KS cases in San Diego County, California during the 6-year period from 1998 to 2003.

Spatial and temporal patterns in pupal and adult production of the dengue vector Aedes aegypti in Kamphaeng Phet, Thailand.

We investigated how temporal and spatial effects confound the functional relationship between pupal and adult populations of Aedes aegypti and thus the value of pupal numbers as predictors of dengue transmission risk in Kamphaeng Phet, Thailand. We found considerable seasonal shifts in productivity of key containers. Tires contained much less pupae in the dry season than in the wet season.

Can we spot a neighborhood from the air? Defining neighborhood structure in Accra, Ghana.

Slums are home to a large fraction of urban residents in cities of developing nations, but little attempt has been made to go beyond a simple slum/non-slum dichotomy, nor to identify slums more quantitatively than through local reputation. We use census data from Accra, Ghana, to create an index that applies the UN-Habitat criteria for a place to be a slum. We use this index to identify neighborhoods on a continuum of slum characteristics and on that basis are able to locate the worst slums in Accra.

ETHNIC RESIDENTIAL PATTERNS AS PREDICTORS OF INTRA-URBAN CHILD MORTALITY INEQUALITY IN ACCRA, GHANA.

As cities of developing nations absorb an increasing fraction of the world's population increase, questions have arisen about the potential for emerging inequalities in health within places that are already suffering from inadequate infrastructure. In this paper we explore the pattern of child mortality inequalities (as a proxy for overall health levels) within a large sub-Saharan African city-Accra, Ghana-and then we examine the extent to which existing residential patterns by ethnicity may be predictive of any observed intra-urban inequalities in child mortality. We find that the spatial variability in child mortality in Accra is especially associated with the pattern of residential separation of the Ga from other ethnic groups, with the Ga having higher levels of mortality than other ethnic groups.

Temporal and geographic patterns of Aedes aegypti (Diptera: Culicidae) production in Iquitos, Peru.

Large-scale longitudinal cohort studies are necessary to characterize temporal and geographic variation in Aedes aegypti (L.) (Diptera: Culicidae) production patterns and to develop targeted dengue control strategies that will reduce disease. We carried out pupal/demographic surveys in a circuit of approximately 6,000 houses, 10 separate times, between January 1999 and August 2002 in the Amazonian city of Iquitos, Peru.

Characteristics of the spatial pattern of the dengue vector, Aedes aegypti, in Iquitos, Peru.

We determine the spatial pattern of Aedes aegypti and the containers in which they develop in two neighborhoods of the Amazonian city of Iquitos, Peru. Four variables were examined: adult Ae. aegypti, pupae, containers positive for larvae or pupae, and all water-holding containers.