Browsing by Author "Ali M"

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Contrasting Epidemiology of Cholera in Bangladesh and Africa.
(2021-Dec-20) Sack DA; Debes AK; Ateudjieu J; Bwire G; Ali M; Ngwa MC; Mwaba J; Chilengi R; Orach CC; Boru W; Mohamed AA; Ram M; George CM; Stine OC; Ministry of Health and Field Epidemiology and Laboratory Training Program, Nairobi, Kenya.; Tanzania Field Epidemiology and Laboratory Training Program, Dar-es-Salaam, Tanzania.; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.; Department of Community Health and Behavioural Sciences, Makerere University School of Public Health, Kampala, Uganda.; Department of Epidemiology and Public Health, School of Medicine, University of Maryland, Baltimore, Maryland, USA.; Department of Integrated Epidemiology, Surveillance, and Public Health Emergencies, Ministry of Health, Kampala, Uganda.; Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.; Meilleur Acces aux Soins de Sante, and Department of Public Health, Faculty of Medicine and Pharmaceutical Sciences, University of Dschang, and Clinical Research Unit, Division of Health Operations Research, Cameroon Ministry of Public Health, Yaoundé, Cameroon.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
In Bangladesh and West Bengal cholera is seasonal, transmission occurs consistently annually. By contrast, in most African countries, cholera has inconsistent seasonal patterns and long periods without obvious transmission. Transmission patterns in Africa occur during intermittent outbreaks followed by elimination of that genetic lineage. Later another outbreak may occur because of reintroduction of new or evolved lineages from adjacent areas, often by human travelers. These then subsequently undergo subsequent elimination. The frequent elimination and reintroduction has several implications when planning for cholera's elimination including: a) reconsidering concepts of definition of elimination, b) stress on rapid detection and response to outbreaks, c) more effective use of oral cholera vaccine and WASH, d) need to readjust estimates of disease burden for Africa, e) re-examination of water as a reservoir for maintaining endemicity in Africa. This paper reviews major features of cholera's epidemiology in African countries which appear different from the Ganges Delta.
Identification of cholera hotspots in Zambia: A spatiotemporal analysis of cholera data from 2008 to 2017.
(2020-Apr) Mwaba J; Debes AK; Shea P; Mukonka V; Chewe O; Chisenga C; Simuyandi M; Kwenda G; Sack D; Chilengi R; Ali M; Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States.; Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.; Zambia National Public Health Institute, Lusaka, Zambia.; University of Zambia, School of Health Sciences, Lusaka, Zambia.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
The global burden of cholera is increasing, with the majority (60%) of the cases occurring in sub-Saharan Africa. In Zambia, widespread cholera outbreaks have occurred since 1977, predominantly in the capital city of Lusaka. During both the 2016 and 2018 outbreaks, the Ministry of Health implemented cholera vaccination in addition to other preventative and control measures, to stop the spread and control the outbreak. Given the limitations in vaccine availability and the logistical support required for vaccination, oral cholera vaccine (OCV) is now recommended for use in the high risk areas ("hotspots") for cholera. Hence, the aim of this study was to identify areas with an increased risk of cholera in Zambia. Retrospective cholera case data from 2008 to 2017 was obtained from the Ministry of Health, Department of Public Health and Disease Surveillance. The Zambian Central Statistical Office provided district-level population data, socioeconomic and water, sanitation and hygiene (WaSH) indicators. To identify districts at high risk, we performed a discrete Poisson-based space-time scan statistic to account for variations in cholera risk across both space and time over a 10-year study period. A zero-inflated negative binomial regression model was employed to identify the district level risk factors for cholera. The risk map was generated by classifying the relative risk of cholera in each district, as obtained from the space-scan test statistic. In total, 34,950 cases of cholera were reported in Zambia between 2008 and 2017. Cholera cases varied spatially by year. During the study period, Lusaka District had the highest burden of cholera, with 29,080 reported cases. The space-time scan statistic identified 16 districts to be at a significantly higher risk of having cholera. The relative risk of having cholera in these districts was significantly higher and ranged from 1.25 to 78.87 times higher when compared to elsewhere in the country. Proximity to waterbodies was the only factor associated with the increased risk for cholera (P<0.05). This study provides a basis for the cholera elimination program in Zambia. Outside Lusaka, the majority of high risk districts identified were near the border with the DRC, Tanzania, Mozambique, and Zimbabwe. This suggests that cholera in Zambia may be linked to movement of people from neighboring areas of cholera endemicity. A collaborative intervention program implemented in concert with neighboring countries could be an effective strategy for elimination of cholera in Zambia, while also reducing rates at a regional level.
Serum vibriocidal responses when second doses of oral cholera vaccine are delayed 6 months in Zambia.
(2021-Jul-22) Mwaba J; Chisenga CC; Xiao S; Ng'ombe H; Banda E; Shea P; Mabula-Bwalya C; Mwila-Kazimbaya K; Laban NM; Alabi P; Chirwa-Chobe M; Simuyandi M; Harris J; Iyer AS; Bosomprah S; Scalzo P; Murt KN; Ram M; Kwenda G; Ali M; Sack DA; Chilengi R; Debes AK; Division of Infectious Diseases, Massachusetts General Hospital, Boston, MA, USA.; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Electronic address: adebes1@jhu.edu.; Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.; Division of Infectious Diseases, Massachusetts General Hospital, Boston, MA, USA; Department of Pediatrics, Harvard Medical School, Boston, MA, USA.; Department of Biomedical Sciences, School of Health Sciences, University of Zambia, Lusaka, Zambia.; Research Department, Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.; Research Department, Centre for Infectious Disease Research in Zambia, Lusaka, Zambia; Department of Biomedical Sciences, School of Health Sciences, University of Zambia, Lusaka, Zambia.; Research Department, Centre for Infectious Disease Research in Zambia, Lusaka, Zambia; London School of Hygiene and Tropical Medicine, United Kingdom.; CIDRZ; Centre for Infectious Disease Research in Zambia (CIDRZ)
Two-dose killed oral cholera vaccines (OCV) are currently being used widely to control cholera. The standard dose-interval for OCV is 2 weeks; however, during emergency use of the vaccine, it may be more appropriate to use the available doses to quickly give a single dose to more people and give a delayed second dose when more vaccine becomes available. This study is an open label, randomized, phase 2 clinical trial of the vibriocidal response induced by OCV, comparing the responses when the second dose was given either 2 weeks (standard dose interval) or 6 months (extended dose interval) after the first dose. Vaccine was administered to healthy participants > 1 year of age living in the Lukanga Swamps area of Zambia. Three age cohorts (<5 years, 5-14 years, and ≥ 15 years) were randomized to the either dose-interval. The primary outcome was the vibriocidal GMT 14 days after the second dose. 156 of 172 subjects enrolled in the study were included in this analysis. The Inaba vibriocidal titers were not significantly different 14 days post dose two for a standard dose-interval GMT: 45.6 (32-64.9), as compared to the GMT 47.6 (32.6-69.3), for the extended dose-interval, (p = 0.87). However, the Ogawa vibriocidal GMTs were significantly higher 14 days post dose two for the extended-dose interval at 87.6 (58.9-130.4) compared to the standard dose-interval group at 49.7 (34.1-72.3), p = 0.04. Vibriocidal seroconversion rates (a > 4-fold rise in vibriocidal titer) were not significantly different between dose-interval groups. This study demonstrated that vibriocidal titers 14 days after a second dose when given at an extended\ dose interval were similar to the standard dose-interval. The findings suggest that a flexible dosing schedule may be considered when epidemiologically appropriate. The trial was registered at Clinical Trials.gov (NCT03373669).