Characterizing hepatitis B virus infection in children in the Democratic Republic of Congo to inform elimination efforts.

Objective: Despite global reductions in hepatitis B virus (HBV) prevalence, an estimated 6.2 million children are infected, two-thirds of whom live in the WHO Africa region. We sought to characterize childhood HBV to inform elimination efforts in the Democratic Republic of Congo (DRC), one of the largest and most populous African countries. Methods: Using the most recent (2013-14) nationally representative Demographic and Health Survey in the DRC, we analyzed HBV surface antigen (HBsAg) on dried blood spots and associated survey data from children aged 6-59 months. We estimated HBsAg-positivity prevalence nationally, regionally, and by potential correlates of infection. We evaluated spatial variation in HBsAg-positivity prevalence, overall and by age, sex, and vaccination status. Findings: Using data from 5,679 children, we found national HBsAg-positivity prevalence was 1.3% (95% CI: 0.9%-1.7%), but ranged from 0.0% in DRC's capital city province, Kinshasa, to 5.6% in northwestern Sud-Ubangi Province. Prevalence among boys (1.8%, 95% CI: 1.2%-2.7%) was double that among girls (0.7%, 95%CI: 0.4%-1.3%). Tetanus antibody-negativity, rurality, and lower household wealth were also significantly associated with higher HBsAg-positivity prevalence. We observed no difference in prevalence by age. Children had higher HBsAg-positivity odds if living with ≥1 HBsAg-positive adult household member (OR: 2.3, 95%CI: 0.7-7.8), particularly an HBsAg-positive mother (OR: 7.2, 95%CI:1.6-32.2). Conclusion: In the largest national survey of HBV among children and household contacts in the DRC, we found that childhood HBV prevalence was 10-60 times the global target of 0.1%. We highlight specific regions and populations for further investigation and focused prevention efforts.

Deep tubewell microbial water quality and access in arsenic mitigation programs in rural Bangladesh.

The objective of this paper is to determine whether deep tubewells installed through arsenic mitigation efforts in rural Bangladesh provide better drinking water microbial quality compared to shallow tubewells. We conducted a stratified random cross-sectional survey of 484 households to assess microbial contamination of deep tubewell water at source and at point of use (POU) compared to shallow tubewell water using the Compartment Bag Test. In addition, we measured storage time, distance, travel time and ownership status among both sets of users to assess deep tubewell efficacy and under what conditions they offer poorer or better water quality. Differences in tubewell characteristics were compared using non-parametric Mann-Whitney U tests and two-proportion Z-tests. Prevalence ratios of microbial contamination stratified by water quality, storage time and distance to tubewells and ownership were estimated using unadjusted Mantel-Haenszel tests. There was no significant difference in microbial contamination between shallow and deep tubewells at source. The presence of POU water microbial contamination in storage containers in deep tubewell households was 1.11 times the prevalence in shallow tubewell storage containers (95% CI = 0.97-1.27). Deep tubewell users stored water longer and walked significantly farther to obtain water compared to shallow tubewell users. Among deep tubewell households, those residing farther away from the source were 1.24 times as likely to drink contaminated water from storage containers compared to those located nearby (95% CI = 1.04-1.48). Our findings suggest that deep tubewells have comparable water quality to shallow tubewells at source, but increasing distance from the household exacerbates risk of microbial contamination at POU.

Environmental factors associated with childhood norovirus diarrhoea in León, Nicaragua.

Norovirus is detected in one in five diarrhoea episodes in children, yet little is known about environmental risk factors associated with this disease, especially in low-income settings. The objective of this study was to examine environmental risk factors, and spatial and seasonal patterns of norovirus diarrhoea episodes in children in León, Nicaragua. We followed a population-based cohort of children under age 5 years for norovirus diarrhoea over a 1-year period. At baseline, characteristics of each household were recorded. Households were geocoded and spatial locations of garbage dumps, rivers, and markets were collected. In bivariate analysis we observed younger children and those with animals in their households were more likely to have experienced norovirus episodes. In adjusted models, younger children remained at higher risk for norovirus episodes, but only modest associations were observed with family and environmental characteristics. We next identified symptomatic children living in the same household and within 500 m buffer zones around the household of another child infected with the same genotype. Norovirus diarrhoea episodes peaked early in the rainy season. These findings contribute to our understanding of environmental factors and norovirus infection.

Association of climate variability and childhood diarrhoeal disease in rural Bangladesh, 2000-2006.

This study examined the effects of meteorological factors, particularly, extreme weather events, on the prevalence of childhood diarrhoeal disease in Matlab, Bangladesh. Logistic regression models were used to examine impacts of temperature, rainfall and the extreme weather factors (the number of hot days and days with heavy rainfall) on childhood diarrhoea from 2000 to 2006 at the bari (cluster of dwellings) level. The results showed that the increases in the number of hot days and days with heavy rainfall were associated with an increase in daily diarrhoea cases by 0·8-3·8% and 1-6·2%, respectively. The results from multivariable stepwise models showed that the extreme weather factors were still positively associated with childhood diarrhoea, while the associations for average temperature and rainfall could be negative after other variables were controlled. The findings showed that not only the intensity, but also the frequency of extreme weather events had significant effects on childhood diarrhoea.

The spatial distribution of overweight and obesity among a birth cohort of young adult Filipinos (Cebu Philippines, 2005): an application of the Kulldorff spatial scan statistic.

OBJECTIVES: The objectives of the study were to test for spatial clustering of obesity in a cohort of young adults in the Philippines, to estimate the locations of any clusters, and to relate these to neighborhood-level urbanicity and individual-level socioeconomic status (SES). SUBJECTS: Data are from a birth cohort of young adult (mean age 22 years) Filipino males (n=988) and females (n=820) enrolled in the Cebu Longitudinal Health and Nutrition Survey. METHODS: We used the Kulldorff spatial scan statistic to detect clusters associated with unusually low or high prevalences of overweight or obesity (defined using body mass index, waist circumference and body fat percentage). Cluster locations were compared to neighborhood-level urbanicity, which was measured with a previously validated scale. Individual-level SES was adjusted for using a principal components analysis of household assets. RESULTS: High-prevalence clusters were typically centered in urban areas, but often extended into peri-urban and even rural areas. There were also differences in clustering by both sex and the measure of obesity used. Evidence of clustering in males, but not females, was much weaker after adjustment for SES.

Effect of deep tube well use on childhood diarrhoea in Bangladesh.

OBJECTIVE: To determine whether the installation of deep tube wells to reduce exposure to groundwater arsenic in rural Bangladesh had an effect on the incidence of childhood diarrhoeal disease. METHODS: Episodes of diarrhoeal disease in children aged under 5 years that occurred on one specified day each month between 2005 and 2006 were reported to community health workers for six rural villages. A geographical information system containing details of household water use and sanitation in the villages was built using data obtained by a global positioning system survey. The information system also included health, spatial and demographic data. A field survey was carried out to determine whether households obtained drinking water from deep tube wells installed in 2005. The effect of deep tube well use on the incidence of childhood diarrhoea was assessed using a random effects negative binomial regression model. FINDINGS: The risk of childhood diarrhoea was 46% lower in the 179 households that used a deep tube well than in the 364 that used a shallow tube well (P=0.032). Neither socioeconomic status, latrine density, population density nor study year had a significant influence on disease risk. The incidence of childhood diarrhoea declined dramatically between 2005 and 2006, irrespective of water source. CONCLUSION: The introduction of deep tube wells to reduce arsenic in drinking water in rural Bangladesh had the additional benefit of lowering the incidence of diarrhoea among young children.

Variations in the effect of incarceration on community gonorrhoea rates, Guilford County, North Carolina, 2005-2006.

Community incarceration rates have been shown to be associated with rates of HIV and sexually transmitted diseases (STDs). Mechanisms underlying this association include transmission by recently released inmates and community disruption resulting from the absence of incarcerated individuals. We studied the 2006 rates of gonorrhoea at the census tract level in Guilford County, North Carolina (NC) with the previous year's incarceration rates as the exposure of interest. We replicated an analysis conducted in Durham, NC, but unlike in Durham found no meaningful association. When terms were added to the model to allow for a non-linear effect, incarceration levels were associated with rates of gonorrhoea (P < 0.05), indicating the effect of incarceration on gonorrhoea rates differs based on the level of incarceration. Using a spatial model, we found evidence that the association varies across the county. The association between incarceration and gonorrhoea varies by the rate of incarceration and geographically.

Implementation of a medical geographic information system: concepts and uses.

This paper introduces a medical geographic information system which has been implemented to enhance public-health research by facilitating the modelling of spatial processes of disease, environment, and healthcare systems in a rural area of Bangladesh. In 1966, a surveillance system was implemented to record all vital demographic events in the study area. Selected information on reproductive and child health, socioeconomic conditions, and health and family-planning interventions is being collected for the surveillance database. This paper discusses the conceptual design of integrating the surveillance database with the medical geographic information system and its use in conducting multidisciplinary health research. The paper is intended to help those who wish to implement a health-based geographic information system to understand the links between people and their environments and to better meet the health needs of target communities.

Implications of health care provision on acute lower respiratory infection mortality in Bangladeshi children.

This study uses a geographic information system to evaluate the effects of health care provision on acute lower respiratory infection (ALRI) mortality in very young children in rural Bangladesh. Since 1988, an ALRI control program has been operating in a rural area of Bangladesh in an effort to decrease morbidity and mortality of children suffering from ALRI. ALRI-specific mortality data for very young children (<2 years of age) were obtained from a surveillance system of the area from 1988 to 1993. The ALRI mortality data were aggregated by clusters of households called baris. In order to avoid bias in the population size of haris, spatial moving averages of ALRI-specific death rates were calculated. The relationships between ALRI death rates and several environmental and health service provision variables were measured using regression analysis. The results show that the ALRI mortality rate was 54% lower in the community-based ALRI control program area than in a comparison area where there was no intervention. Greater access to allopathic practitioners was related to lower ALRI mortality rates while access to indigenous practitioners was related to higher mortality. In conclusion, the benefit of the community-based ALRI control program, using a simple case management strategy and improved access to allopathic practitioners, should be replicated in other rural areas of Bangladesh in an effort to reduce child ALRI mortality.

Are the environmental niches of Vibrio cholerae O139 different from those of Vibrio cholerae O1 El Tor?

BACKGROUND: Vibrio cholerae are known to be normal inhabitants of surface water. However, the environmental niches of the different strains of cholera are not well known, and therefore, populations at risk for cholera outbreaks cannot be clearly identified. METHODS: This study identifies environmental risk factors for cholera caused by V. cholerae O1 El Tor and O139 and environmental niches of the two strains present in Matlab, a cholera endemic area of Bangladesh. The study year was 1993, the year that the O139 strain first appeared in the study area. Patients who had either strain of cholera identified in a laboratory were included in the study. A geographic information system was used to map the household locations of the patients, to describe the human sanitary environment and population density, and to address potential anthropogenic and environmental risk factors of the disease. Spatial point pattern and exploratory spatial data analysis techniques were used to define the environmental niches of the two cholera strains. RESULTS: The study suggests the niches of O1 El Tor and O139 strains of V. cholerae appear to be similar, based on common environmental risk factors. CONCLUSIONS: The results of this study support a theory that O1 El Tor could possibly be replaced by the newer O139 strain in the future.

Diarrheal disease risk in Matlab, Bangladesh.

The objective of this research project is to assess risk for diarrheal disease in rural Bangladesh by analyzing the complex and dynamic interaction of biological, socioeconomic, cultural/behavioral and environmental factors over time and space. Risk factors of cholera and non-cholera water diarrheal disease are calculated to compare the relative importance of risk for several independent variables. Diarrheal disease data were collected for people who were hospitalized at the International Centre for Diarrhoeal Disease Research (ICDDR) hospital from January 1, 1992 to December 31, 1994. Using laboratory and hospital records, cases were assigned to one of two diarrhea disease categories (cholera or non-cholera watery diarrhea) that were used as dependent variables in the analysis stage of the research. Age-matched individuals were randomly chosen from the community to be controls. Information was collected for independent variables that were hypothesized to be related to watery diarrhea. This information was collected by administering questionnaires, obtaining secondary data from the ICDDR's demographic surveillance system records and community health worker record books and calculating variables using a geographic information system database. Sanitation and water availability and use are extremely important in the effort to reduce secondary cholera and non-cholera, watery diarrhea transmission. Water use and availability variables were more important for non-cholera watery diarrheal risk than for cholera but nevertheless they were important for both. Socioeconomic status is an important indirect cause of both of these diseases because poverty is the root cause of many of the other variables, such as lack of sanitation and clean water. Flood-control was related to both types of diarrhea but it is not understood why. Since the Bangladesh Flood Action Plan will continue to build and maintains flood-control embankments, it is important to investigate whether there is a pattern to this relationship throughout the country and to investigate why the relationship exists.

Use of oxygen-15 to measure oxygen-carrying capacity of blood substitutes in vivo.

A method for determining oxygen-carrying capacity of blood substitutes has been developed using the short-lived cyclotron-produced positron-emitting isotope 15O. This method measures the oxygen-carrying capacity of the blood substitutes in vivo in the presence of red blood cells and allows determination of changes in the oxygen-carrying capacity over time after exchange transfusion. This method is applied to the blood substitutes of liposome-encapsulated hemoglobin (LEH) and cell-free hemoglobin (Hb). We have used 15O (half-life of 2 min) to quantitate the lung uptake and tissue delivery of [15O2]LEH. Lung uptake studies were performed in intubated, catheterized rats after a 40% exchange transfusion of bovine LEH (LEBH; 0.68 g Hb/kg body wt), human hemolysate LEH (LEHH; 1.0 g Hb/kg body wt), or free bovine hemoglobin (SFHS; 0.56 g Hb/kg body wt). A bolus inhalation of 15O2 (3-5 mCi) was given at 15 min, 3 h, and 24 h post-transfusion. Arterial blood samples were collected, spun, and separated into LEH, red blood cell, and plasma fractions. 15O activity and hemoglobin content were determined for each fraction. Oxygen-carrying capacity was calculated as a percentage of the original red blood cell fraction removed. For LEBH, the carrying capacity was 15% at 15 min, 13% at 3 h, and 1% at 24 h. For LEHH, the carrying capacity was 30% at 15 min, 26% at 3 h, and 19% at 24 h. The marked decrease in carrying capacity at 24 h for LEBH compared with LEHH was attributable to the increased formation of methemoglobin in the circulating LEBH rather than increased removal from circulation, because total hemoglobin concentrations measured for both LEH samples decreased at a similar rate during the 24 h. The presence of methemoglobin reductase and other naturally occurring antioxidants in the LEHH may be responsible for maintaining the higher levels of oxyhemoglobin. Oxygen-carrying capacity for SFHS also decreased over time but at a much sharper rate compared with both LEH formulations. The carrying capacity for SFHS of 8% measured at 15 min decreased to 0.3% at 3 h and undetectable levels at 24 h. This sharper decrease in carrying capacity for SFHS is attributable to the rapid removal of the hemoglobin from circulation.