Biomedical subjects

Mohammad Yunus

Publications and source records attributed to Mohammad Yunus.

13 recordsLinked to original sources

PubMed2006

Application of Poisson kriging to the mapping of cholera and dysentery incidence in an endemic area of Bangladesh.

BACKGROUND: Disease maps can serve to display incidence rates geographically, to inform on public health provision about the success or failure of interventions, and to make hypothesis or to provide evidences concerning disease etiology. Poisson kriging was recently introduced to filter the noise attached to rates recorded over sparsely populated administrative units. Its benefit over simple population-weighted averages and empirical Bayesian smoothers was demonstrated by simulation studies using county-level cancer mortality rates. This paper presents the first application of Poisson kriging to the spatial interpolation of local disease rates, resulting in continuous maps of disease rate estimates and the associated prediction variance. The methodology is illustrated using cholera and dysentery data collected in a cholera endemic area (Matlab) of Bangladesh. RESULTS: The spatial analysis was confined to patrilineally-related clusters of households, known as baris, located within 9 kilometers from the Matlab hospital to avoid underestimating the risk of disease incidence, since patients far away from the medical facilities are less likely to travel. Semivariogram models reveal a range of autocorrelation of 1.1 km for dysentery and 0.37 km for cholera. This result translates into a cholera risk map that is patchier than the dysentery map that shows a large zone of high incidence in the south-central part of the study area, which is quasi-urban. On both maps, lower risk values are found in the Northern part of the study area, which is also the most distant from the Matlab hospital. The weaker spatial continuity of cholera versus dysentery incidence rates resulted in larger kriging variance across the study area. CONCLUSION: The approach presented in this paper enables researchers to incorporate the pattern of spatial dependence of incidence rates into the mapping of risk values and the quantification of the associated uncertainty. Differences in spatial patterns, in particular the range of spatial autocorrelation, reflect differences in the mode of transmission of cholera and dysentery. Our risk maps for cholera and dysentery incidences should help identifying putative factors of increased disease incidence, leading to more effective prevention and remedial actions in endemic areas.

Bangladesh↗

PubMed2006

Relationship between neighbourhood-level killed oral cholera vaccine coverage and protective efficacy: evidence for herd immunity.

OBJECTIVES: The effectiveness of vaccines in populations must consider both direct and indirect protection. This study reanalyses data from a large individually randomized oral cholera vaccine trial that was conducted in rural Bangladesh from 1985 to 1990. A recent analysis of the results of that trial showed that the proportion of people in household clusters who received the vaccine was inversely related to placebo incidence during the first year of surveillance, which was attributed to herd immunity. METHODS: In this study we measure the relationship between neighbourhood-level oral cholera vaccine coverage and protective efficacy (PE) during a 2 year follow-up period, controlling for known effect modifiers. We link trial data to a household geographic information system to facilitate the neighbourhood-level analysis. Findings Neighbourhood-level PE can be partially explained by vaccine coverage after adjusting for ecological variables. CONCLUSIONS: The inverse relationship between vaccine coverage and efficacy illustrates that people living in high-coverage areas may be indirectly protected from cholera because people living around them are vaccinated.

Adult↗

PubMed2006

Efficacy calculation in randomized trials: global or local measures?

This study tests whether the effect of a vaccine trial varies in space and why. Analytical z-score maps identify unusually high- and low-efficacy values in a trial area. Relationships between neighborhood efficacy and ecological variables are measured to explain why efficacy varies in space. Efficacy was found to vary regardless of neighborhood size and the variation is related to several ecological determinants. Local efficacy measures can help public health practitioners make better decisions about when and where to vaccinate populations. The concepts offered in this study are pertinent for any health intervention trial, not just vaccines.

Adolescent↗

PubMed2006

Zinc supplementation and serum zinc during diarrhea.

OBJECTIVE: Zinc deficiency is very common in developing countries and is more pronounced during an episode of diarrhea. Supplementation with zinc improves diarrhea and might correct zinc deficiency in both the short and longer term. METHOD: We conducted a nested study within a cluster randomized treatment trial. Fifty children with diarrhea living in the zinc treated clusters, 50 children with diarrhea living in control clusters, and 50 healthy children living in the control clusters were enrolled. We assessed serum zinc at the start of the diarrhea episode, which was 1-3 days after supplementation began in zinc treated children, and again one week after the diarrhea ended and supplementation ceased. Baseline characteristics and serum zinc concentration were assessed. RESULTS: Serum zinc was low in 44% of healthy children at the first blood draw. Compared to healthy controls, serum zinc was 3.1 mmol/L higher among children with diarrhea who were supplemented with zinc at first blood draw and 1.3 mmol/L higher 3 weeks later. CONCLUSION: Zinc supplementation enhances serum zinc concentration when given as a treatment for diarrhea and helps children maintain a more adequate zinc status during the convalescent period.

Child, Preschool↗

PubMed2006

Prevalence of arsenic exposure and skin lesions. A population based survey in Matlab, Bangladesh.

STUDY OBJECTIVE: To assess prevalence of arsenic exposure through drinking water and skin lesions, and their variation by geographical area, age, sex, and socioeconomic conditions. DESIGN, SETTING, AND PARTICIPANTS: Skin lesion cases were identified by screening the entire population above 4 years of age (n = 166,934) living in Matlab, a rural area in Bangladesh, during January 2002 and August 2003. The process of case identification involved initial skin examinations in the field, followed by verification by physicians in a clinic, and final confirmation by two independent experts reviewing photographs. The tubewell water arsenic concentrations (n = 13,286) were analysed by atomic absorption spectrometry. Drinking water history since 1970 was obtained for each person. Exposure information was constructed using drinking water histories and data on water arsenic concentrations. MAIN RESULTS: The arsenic concentrations ranged from <1 to 3644 microg/l, and more than 70% of functioning tubewells exceeded the World Health Organisation guideline of 10 microg/l. Arsenic exposure had increased steadily from 1970s to the late 1990s, afterwards a decrease could be noted. In total, 504 skin lesions cases were identified, and the overall crude prevalence was 3/1000. Women had significantly higher cumulative exposure to arsenic, while men had significantly higher prevalence of skin lesions (SMR 158, 95% CI 133 to 188). The highest prevalence occurred in 35-44 age groups for both sexes. Arsenic exposure and skin lesions had a positive association with socioeconomic groups and achieved educational level. CONCLUSIONS: The result showed sex, age, and socioeconomic differentials in both exposure and skin lesions. Findings clearly showed the urgency of effective arsenic mitigation activities.

Adolescent↗

PubMed2005

Drug resistance of Mycobacterium tuberculosis in selected urban and rural areas in Bangladesh.

The magnitude of anti-tuberculosis drug resistance in Bangladesh is not precisely known. We studied the drug resistance patterns of Mycobacterium tuberculosis in an urban and a rural area of Bangladesh. A tuberculosis (TB) surveillance system has been set up in a population of 106,000 in rural Matlab and in a TB clinic in urban Dhaka. Trained field workers interviewed all persons > or =15 y at Matlab to detect suspected cases of tuberculosis (cough >21 d) and sputum samples were examined for acid-fast bacilli (AFB). The first 3 AFB positive patients daily from the urban clinic were included. AFB positive cases diagnosed between June 2001 and June 2003 from both settings were cultured and drug susceptibility tests were performed. Of 657 isolates, resistance to 1 or more drugs was observed in 48.4% of isolates. Resistance to streptomycin, isoniazid, ethambutol and rifampicin was observed in 45.2%, 14.2%, 7.9% and 6.4% of isolates, respectively. Multidrug resistance was observed in 5.5% of isolates. It was significantly higher among persons who previously had received tuberculosis treatment of > or =1 month (15.4% vs 3.0%, adjusted OR: 6.12, 95% CI: 3.03-12.34). The magnitude of anti-tuberculosis drug resistance in Bangladesh is high. Further evaluation is needed to explain the high proportion of streptomycin resistant M. tuberculosis. Appropriate measures to control and prevent drug resistant tuberculosis in Bangladesh to reduce mortality and transmission are warranted.

Adolescent↗

PubMed2004

Variation of toxigenic Vibrio cholerae O1 in the aquatic environment of Bangladesh and its correlation with the clinical strains.

The diversity of toxigenic V. cholerae O1 in the aquatic environment of Bangladesh is not known. A total of 18 environmental and 18 clinical strains of toxigenic V. cholerae O1 were isolated simultaneously from four different geographical areas and tested for variation by the pulsed-field gel electrophoresis method. Environmental strains showed diversified profiles and one of the profiles was common to some environmental strains and most clinical strains. It appears that one clone has an advantage over others to cause disease. These findings suggest that the study of the molecular ecology of V. cholerae O1 in relation to its environmental reservoir is important in identifying virulent strains that cause disease.

Animals↗

PubMed2004

Zinc therapy for diarrhoea increased the use of oral rehydration therapy and reduced the use of antibiotics in Bangladeshi children.

Excessive use of antibiotics for diarrhoea is a major contributing factor towards increasing rates of antimicrobial resistance in developing countries. Zinc therapy for diarrhoea has been shown to be beneficial in controlled efficacy trials, and it is of interest to determine if availability of zinc syrup for treatment of diarrhoea would satisfy the demand for a 'medicine' for diarrhoea, thus reducing the use of antibiotics, without competing with the use of oral rehydration therapy (ORT). This community-based controlled trial was conducted from November 1998 to October 2000, and all children aged 3-59 months in the study area were included. In this trial, the availability of zinc supplements, along with ORT and appropriate education programmes, was associated with significantly higher use of ORT and lower use of antibiotics.

Anti-Bacterial Agents↗

PubMed2003

Simultaneous weekly supplementation of iron and zinc is associated with lower morbidity due to diarrhea and acute lower respiratory infection in Bangladeshi infants.

Given the high prevalence of micronutrient deficiencies and infectious diseases in infants in developing countries, an evaluation of the efficacy of different micronutrient formulations on infant morbidity is a priority. The efficacy of weekly supplementation of four different micronutrient formulations on diarrhea and acute lower respiratory infection (ALRI) morbidity was evaluated in Bangladeshi infants. In a double-blind, randomized, controlled community trial, 799 infants aged 6 mo were randomly assigned to one of the following 5 groups: 1) 20 mg elemental iron with 1 mg riboflavin, 2) 20 mg elemental zinc with 1 mg riboflavin, 3) 20 mg iron and 20 mg zinc with 1 mg riboflavin, 4) a micronutrient mix (MM) containing 20 mg iron, 20 mg zinc, 1 mg riboflavin along with other minerals and vitamins and 5) a control treatment, 1 mg riboflavin only. Health workers visited each infant weekly until age 12 mo to feed the supplement and to collect data on diarrhea and ALRI morbidity. Hemoglobin, serum ferritin and serum zinc levels of a sample of infants were measured at 6 and 12 mo. Compared with the control group, at 12 mo, serum ferritin levels were higher in the iron + zinc group, and serum zinc levels were higher in the zinc and iron + zinc groups. Simultaneous supplementation with iron + zinc was associated with lower risk of severe diarrhea, 19% lower in all infants and 30% lower in less well-nourished infants with weight-for-age Z-score below -1. Iron + zinc supplementation was also associated with 40% lower risk of severe ALRI in less well-nourished infants. MM supplementation was associated with a 15% higher risk of diarrhea in all infants and 22% higher risk in less well-nourished infants. Intermittent simultaneous supplementation with iron + zinc seems promising; it will be useful to determine whether higher doses would provide greater benefits.

Acute Disease↗

PubMed2002

Effect of zinc supplementation started during diarrhoea on morbidity and mortality in Bangladeshi children: community randomised trial.

OBJECTIVE: To evaluate the effect on morbidity and mortality of providing daily zinc for 14 days to children with diarrhoea. DESIGN: Cluster randomised comparison. SETTING: Matlab field site of International Center for Diarrhoeal Disease Research, Bangladesh. PARTICIPANTS: 8070 children aged 3-59 months contributed 11 881 child years of observation during a two year period. INTERVENTION: Children with diarrhoea in the intervention clusters were treated with zinc (20 mg per day for 14 days); all children with diarrhoea were treated with oral rehydration therapy. MAIN OUTCOME MEASURES: Duration of episode of diarrhoea, incidence of diarrhoea and acute lower respiratory infections, admission to hospital for diarrhoea or acute lower respiratory infections, and child mortality. RESULTS: About 40% (399/1007) of diarrhoeal episodes were treated with zinc in the first four months of the trial; the rate rose to 67% (350/526) in month 5 and to >80% (364/434) in month 7 and was sustained at that level. Children from the intervention cluster received zinc for about seven days on average during each episode of diarrhoea. They had a shorter duration (hazard ratio 0.76, 95% confidence interval 0.65 to 0.90) and lower incidence of diarrhoea (rate ratio 0.85, 0.76 to 0.96) than children in the comparison group. Incidence of acute lower respiratory infection was reduced in the intervention group but not in the comparison group. Admission to hospital of children with diarrhoea was lower in the intervention group than in the comparison group (0.76, 0.59 to 0.98). Admission for acute lower respiratory infection was lower in the intervention group, but this was not statistically significant (0.81, 0.53 to 1.23). The rate of non-injury deaths in the intervention clusters was considerably lower (0.49, 0.25 to 0.94). CONCLUSIONS: The lower rates of child morbidity and mortality with zinc treatment represent substantial benefits from a simple and inexpensive intervention that can be incorporated in existing efforts to control diarrhoeal disease.

Antidiarrheals↗

PubMed2002

The spatial epidemiology of cholera in an endemic area of Bangladesh.

This paper defines high-risk areas of cholera based on environmental risk factors of the disease in an endemic area of Bangladesh. The risk factors include proximity to surface water, high population density, and low educational status, which were identified in an earlier study by the authors. Cholera data were analyzed by spatially referenced extended household units for two time periods, 1983-1987 and 1992-1996. These periods were chosen because they had different dominant cholera agents. From 1983-1987 classical cholera was dominant and from 1992-1996 El Tor was dominant. By defining high-risk areas based on risk factors, this study builds a spatial risk model for cholera. The model is then evaluated based on the locations of observed cholera cases. The study also identifies the determinants of death due to cholera for the two different time periods dominated by the different cholera agents. The modeled risk areas that were based on the risk factors were found to correspond with actual distributions of cholera morbidity and mortality. The high-risk areas of the dominant cholera agents are relatively stable over time. However, from 1983-1987 El Tor cholera, which was not the dominant agent during that period, was not associated with high-risk areas, suggesting that the El Tor habitat may have changed over time. The case fatality rate for cholera was related to proximity to a diarrhea treatment hospital in the study area.

Bangladesh↗

PubMed2002

Identifying environmental risk factors for endemic cholera: a raster GIS approach.

The bacteria that cause cholera are known to be normal inhabitants of surface water, however, the environmental risk factors for different biotypes of cholera are not well understood. This study identifies environmental risk factors for cholera in an endemic area of Bangladesh using a geographic information systems (GIS) approach. The study data were collected from a longitudinal health and demographic surveillance system and the data were integrated within a geographic information system database of the research area. Two study periods were chosen because they had different dominant biotypes of the disease. From 1992 to 1996 El Tor cholera was dominant and from 1983 to 1987 classical cholera was dominant. The study found the same three risk factors for the two biotypes of cholera including proximity to surface water, high population density, and poor educational level. The GIS database was used to measure the risk factors and spatial filtering techniques were employed. These robust spatial methods are offered as an example for future epidemiological research efforts that define environmental risk factors for infectious diseases.

Bangladesh↗

PubMedDate not supplied

Herd immunity conferred by killed oral cholera vaccines in Bangladesh: a reanalysis.

BACKGROUND: Decisions about the use of killed oral cholera vaccines, which confer moderate levels of direct protection to vaccinees, can depend on whether the vaccines also provide indirect (herd) protection when high levels of vaccine coverage are attained. We reanalysed data from a field trial in Bangladesh to ascertain whether there is evidence of indirect protection from killed oral cholera vaccines. METHODS: We analysed the first year of surveillance data from a placebo-controlled trial of B subunit-killed whole-cell and killed whole-cell-only oral cholera vaccines in children and adult women in Bangladesh. We calculated whether there was an inverse, monotonic trend for the relation between the level of vaccine coverage in a residential cluster and the incidence of cholera in individual vaccine recipients or placebo recipients residing in the cluster after controlling for potential confounding variables. FINDINGS: Vaccine coverage of the targeted population ranged from 4% to 65%. Incidence rates of cholera among placebo recipients were inversely related to levels of vaccine coverage (7.01 cases per 1000 in the lowest quintile of coverage vs 1.47 cases per 1000 in the highest quintile; p<0.0001 for trend). Receipt of vaccine by an individual and the level of vaccine coverage of the individual's cluster were independently related to a reduced risk of cholera. Moreover, after adjustment for the level of vaccine coverage of the cluster, vaccine protective efficacy remained significant (55% [95% CI 41-66], p<0.0001). INTERPRETATION: In addition to providing direct protection to vaccine recipients, killed oral cholera vaccines confer significant herd protection to neighbouring non-vaccinated individuals. Use of these vaccines could have a major effect on the burden of cholera in endemic settings.

Administration, Oral↗