Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
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Incidence and predictors of attrition from HIV treatment among adults living with HIV in high-caseload facilities following implementation of universal test and treat strategy in Ethiopia: A prospective cohort study
Bekele A , Ahmed I , Tefera F , Yimam JA , Woldeselassie FT , Abera G , Ahmed J , Mekonnen A , Haile A , Yohannes F , Getachew M , Abdella S , Shah M . HIV Med 2024 BACKGROUND: The introduction of universal test and treat (UTT) strategy has demonstrated a reduction in attrition in some low-resource settings. UTT was introduced in Ethiopia in 2016. However, there is a paucity of information regarding the magnitude and predictors of attrition from HIV treatment in Ethiopia. This study aims to assess the incidence and predictors of attrition from HIV treatment among adults living with HIV (PLHIV) in high-caseload facilities following the implementation of universal test and treat strategy in Ethiopia from March 2019 to June 2020. METHODS: A prospective cohort of individuals in HIV care from 39 high-caseload facilities in Oromia, Amhara, Tigray, Addis Ababa and Dire Dawa regions of Ethiopia was conducted for 12 months. Participants were adults aged 15 year and older who were first testers recruited for 3 months from March to June 2019. Subsequent follow-up was for 12 months, with data collected on sociodemographic and clinical conditions at baseline, 6 and 12 months and attrition at 6 and 12 months. We defined attrition as discontinuation from follow-up care due to loss to follow-up, dropout or death. Data were collected using Open Data Kit at field level and aggregated centrally. Kaplan-Meier survival analysis was employed to assess survival probability to the time of attrition from treatment. The Cox proportional hazards regression model was used to measure association of baseline predictor variables with the proportion of antiretroviral therapy (ART) patients retained in ART during the follow up period. RESULTS: The overall incidence rate for attrition from HIV treatment among the study participants during 12 months of follow-up was 5.02 cases per 1000 person-weeks [95% confidence interval (CI): 4.44-5.68 per 1000 person-weeks]. Study participants from health facilities in Oromia and Addis Ababa/Dire Dawa had 68% and 51% higher risk of attrition from HIV treatment compared with participants from the Amhara region, respectively [adjusted hazard ratio (AHR) = 1.68, 95% CI: 1.22-2.32 and AHR = 1.51, 95% CI: 1.05-2.17, respectively]. Participants who did not have a child had a 44% higher risk of attrition compared with those who had a child (AHR = 1.44, 95% CI: 1.12-1.85). Individuals who did not own mobile phone had a 37% higher risk of attrition than those who owned a mobile phone (AHR = 1.37, 95% CI: 1.02-1.83). Ambulatory/bedridden functional status at the time of diagnosis had a 44% higher risk of attrition compared with participants with a working functional status (AHR = 1.44, 95% CI: 1.08-1.92) at any time during the follow-up period. CONCLUSION: The overall incidence of attrition among people living with HIV enrolled into HIV treatment was not as high as what was reported by other studies. Independent predictors of attrition were administrative regions in Ethiopia where health facilities are located, not having a child, not owning a mobile phone and being ambulatory/bedridden functional status at the time of diagnosis. Concerted efforts should be taken to reduce the magnitude of attrition from HIV treatment and address its drivers. |
Applicability of selected Brighton Collaboration case definitions in low-resource settings: A prospective hospital-based active surveillance in Addis Ababa, Ethiopia
Sintayehu K , Shaum A , Bonger ZT , Dagnachew Zeleke E , Mamo BT , Anito AA , Bekele D , Longley AT , Gashaw H , Alemu A , Degefaw D , Wang SH , Huang WT . Vaccine 2024 INTRODUCTION: Standardizing case definitions for priority vaccine safety conditions facilitates uniform evaluation and consolidation of data obtained from different settings. The Brighton Collaboration case definitions (BCCD) were created to support this harmonization and enable classification from level 1 (most certain) to level 5 (not a case) of certainty. Assessing the performance of BCCD in practice is critical, particularly in resource-limited settings, where many new vaccines may be introduced without prior monitoring in high-income countries. We assessed the performance of BCCD in Addis Ababa, Ethiopia, as applicable to COVID-19 and other vaccines. METHODS: Active surveillance was conducted at Tikur Anbessa Specialized Hospital, the largest referral hospital in Ethiopia. During June 1, 2022-May 31, 2023, three trained physicians prospectively identified patients eligible for COVID-19 vaccination (regardless of vaccine receipt) who presented with one or more of eleven pre-specified adverse events of special interest (AESI) from the emergency department and inpatient wards. Standardized data collection forms were used to capture patient information and assign level of certainty (LOC), regardless of vaccination status for COVID-19. We conducted descriptive analysis to characterize cases and the LOCs reached for each AESI. RESULTS: We detected 203 AESI cases. The most detected conditions were thrombosis and thromboembolism (n = 100, 49 %) and generalized convulsions (n = 38, 19 %). Ninety-six percent of the cases were confirmed at levels 1-3 (n = 187) or level 5 (n = 9) LOC. Non-classifiable (level 4) cases were observed for pericarditis (n = 2), encephalitis (n = 2), myelitis (n = 2), and generalized convulsion (n = 1). CONCLUSION: The BCCD were successfully applied in > 95 % of cases in a large referral hospital in Ethiopia, with generalized convulsion, pericarditis, and encephalomyelitis as the exceptions. We recommend further evaluation in other low-resource settings, particularly in rural or non-referral hospitals, to gain additional insights into performance of these definitions for revision or adaptation, as needed. |
Regional and temporal variations in COVID-19 cases and deaths in Ethiopia: Lessons learned from the COVID-19 enhanced surveillance and response
Teka G , Woldeab A , Dereje N , Eshetu F , Gizachew L , Tazu Z , Lisanwork L , Tigabu E , Gebeyehu A , Tayachew A , Biru M , Berkessa T , Keraleme A , Bikale F , Shure W , Agune A , Haile B , Addis B , Moges M , Gonta M , Hailemariam A , Binkley L , Nawaz S , Wang SH , Mekuria Z , Aklilu A , Aliy J , Lulseged S , Girmay A , Patrick A , Amare B , Delelegn H , Daves S , Yimer G , Abate E , Wossen M , Melaku Z , Gebreyes W , Williams DE , Abayneh A . PLOS Glob Public Health 2024 4 (5) e0003175 BACKGROUND: The COVID-19 pandemic is one of the most devastating public health emergencies of international concern to have occurred in the past century. To ensure a safe, scalable, and sustainable response, it is imperative to understand the burden of disease, epidemiological trends, and responses to activities that have already been implemented. We aimed to analyze how COVID-19 tests, cases, and deaths varied by time and region in the general population and healthcare workers (HCWs) in Ethiopia. METHODS: COVID-19 data were captured between October 01, 2021, and September 30, 2022, in 64 systematically selected health facilities throughout Ethiopia. The number of health facilities included in the study was proportionally allocated to the regional states of Ethiopia. Data were captured by standardized tools and formats. Analysis of COVID-19 testing performed, cases detected, and deaths registered by region and time was carried out. RESULTS: We analyzed 215,024 individuals' data that were captured through COVID-19 surveillance in Ethiopia. Of the 215,024 total tests, 18,964 COVID-19 cases (8.8%, 95% CI: 8.7%- 9.0%) were identified and 534 (2.8%, 95% CI: 2.6%- 3.1%) were deceased. The positivity rate ranged from 1% in the Afar region to 15% in the Sidama region. Eight (1.2%, 95% CI: 0.4%- 2.0%) HCWs died out of 664 infected HCWs, of which 81.5% were from Addis Ababa. Three waves of outbreaks were detected during the analysis period, with the highest positivity rate of 35% during the Omicron period and the highest rate of ICU beds and mechanical ventilators (38%) occupied by COVID-19 patients during the Delta period. CONCLUSIONS: The temporal and regional variations in COVID-19 cases and deaths in Ethiopia underscore the need for concerted efforts to address the disparities in the COVID-19 surveillance and response system. These lessons should be critically considered during the integration of the COVID-19 surveillance system into the routine surveillance system. |
Resistance of Anopheles stephensi to selected insecticides used for indoor residual spraying and long-lasting insecticidal nets in Ethiopia
Teshome A , Erko B , Golassa L , Yohannes G , Irish SR , Zohdy S , Yoshimizu M , Dugassa S . Malar J 2023 22 (1) 218 BACKGROUND: Malaria, transmitted by the bite of infective female Anopheles mosquitoes, remains a global public health problem. The presence of invasive Anopheles stephensi, capable of transmitting Plasmodium vivax and Plasmodium falciparum, was first reported in Ethiopia in 2016. The ecology of this mosquito species differs from that of Anopheles arabiensis, the primary malaria vector in Ethiopia. This study aimed to evaluate the efficacy of selected insecticides, which are used in indoor residual spraying (IRS) and selected long-lasting insecticidal nets (LLINs) for malaria vector control against adult An. stephensi. METHODS: Anopheles stephensi mosquitoes were collected as larvae and pupae from Awash Subah Kilo Town and Haro Adi village, Ethiopia. Adult female An. stephensi, reared from larvae and pupae collected from the field, aged 3-5 days were exposed to impregnated papers of IRS insecticides (propoxur 0.1%, bendiocarb 0.1%, pirimiphos-methyl 0.25%), and insecticides used in LLINs (alpha-cypermethrin 0.05%, deltamethrin 0.05% and permethrin 0.75%), using diagnostic doses and WHO test tubes in a bio-secure insectary at Aklilu Lemma Institute of Pathobiology, Addis Ababa University. For each test and control tube, batches of 25 female An. stephensi were used to test each insecticide used in IRS. Additionally, cone bioassay tests were conducted to expose An. stephensi from the reared population to four brands of LLINs, MAGNet™ (alpha-cypermethrin), PermaNet(®) 2.0 (deltamethrin), DuraNet(©) (alpha-cypermethrin) and SafeNet(®) (alpha-cypermethrin). A batch of ten sugar-fed female mosquitoes aged 2-5 days was exposed to samples taken from five positions/sides of a net. The data from all replicates were pooled and descriptive statistics were used to describe features of the data. RESULTS: All An. stephensi collected from Awash Subah Kilo Town and Haro Adi village (around Metehara) were resistant to all tested insecticides used in both IRS and LLINs. Of the tested LLINs, only MAGNet™ (alpha-cypermethrin active ingredient) caused 100% knockdown and mortality to An. stephensi at 60 min and 24 h post exposure, while all other net brands caused mortality below the WHO cut-off points (< 90%). All these nets, except SafeNet(®), were collected during LLIN distribution for community members through the National Malaria Programme, in December 2020. CONCLUSIONS: Anopheles stephensi is resistant to all tested insecticides used in IRS and in the tested LLIN brands did not cause mosquito mortality as expected, except MAGNet. This suggests that control of this invasive vector using existing adult malaria vector control methods will likely be inadequate and that alternative strategies may be necessary. |
System and facility readiness assessment for conducting active surveillance of adverse events following immunization in Addis Ababa, Ethiopia
Zeleke ED , Yimer G , Lisanework L , Chen RT , Huang WT , Wang SH , Bennett SD , Makonnen E . Int Health 2023 BACKGROUND: To help distinguish vaccine-related adverse events following immunization (AEFI) from coincidental occurrences, active vaccine pharmacovigilance (VP) prospective surveillance programs are needed. From February to May 2021, we assessed the system and facility readiness for implementing active AEFI VP surveillance in Addis Ababa, Ethiopia. METHODS: Selected hospitals were assessed using a readiness assessment tool with scoring measures. The site assessment was conducted via in-person interviews within the specific departments in each hospital. We evaluated the system readiness with a desk review of AEFI guidelines, Expanded Program for Immunization Guidelines and Ethiopian Food and Drug Administration and Ethiopian Public Health Institute websites. RESULTS: Of the hospitals in Addis Ababa, 23.1% met the criteria for our site assessment. During the system readiness assessment, we found that essential components were in place. However, rules, regulations and proclamations pertaining to AEFI surveillance were absent. Based on the tool, the three hospitals (A, B and C) scored 60.6% (94/155), 48.3% (75/155) and 40% (62/155), respectively. CONCLUSIONS: Only one of three hospitals assessed in our evaluation scored >50% for readiness to implement active AEFI surveillance. We also identified the following areas for improvement to ensure successful implementation: training, making guidelines and reporting forms available and ensuring a system that accommodates paper-based and electronic-based recording systems. |
Adapting strategies for effective and efficient pediatric HIV case finding in low prevalence countries: risk screening tool for testing children presenting at high-risk entry points in Ethiopia
Teferi W , Gutreuter S , Bekele A , Ahmed J , Ayalew J , Gross J , Kumsa H , Antefe T , Mengistu S , Mirkovic K , Dziuban EJ , Ross C , Belay Z , Tilahun T , Kassa D , Hrapcak S . BMC Infect Dis 2022 22 (1) 480 BACKGROUND: Implementing effective and efficient case-finding strategies is crucial to increasing pediatric antiretroviral therapy coverage. In Ethiopia, universal HIV testing is conducted for children presenting at high-risk entry points including malnutrition treatment, inpatient wards, tuberculosis (TB) clinics, index testing for children of positive adults, and referral of orphans and vulnerable children (OVC); however, low positivity rates observed at inpatient, malnutrition and OVC entry points warrant re-assessing current case-finding strategies. The aim of this study is to develop HIV risk screening tool applicable for testing children presenting at inpatient, malnutrition and OVC entry points in low-HIV prevalence settings. METHODS: The study was conducted from May 2017-March 2018 at 29 public health facilities in Amhara and Addis Ababa regions of Ethiopia. All children 2-14years presenting to five high-risk entry points including malnutrition treatment, inpatient wards, tuberculosis (TB) clinics, index testing for children of positive adults, and referral of orphans and vulnerable children (OVC) were enrolled after consent. Data were collected from registers, medical records, and caregiver interviews. Screening tools were constructed using predictors of HIV positivity as screening items by applying both logistic regression and an unweighted method. Sensitivity, specificity and number needed to test (NNT) to identify one new child living with HIV (CLHIV) were estimated for each tool. RESULTS: The screening tools had similar sensitivity of 95%. However, the specificities of tools produced by logistic regression methods (61.4 and 65.6%) which are practically applicable were higher than those achieved by the unweighted method (53.6). Applying these tools could result in 5863% reduction in the NNT compared to universal testing approach while maintaining the overall number of CLHIV identified. CONCLUSION: The screening tools developed using logistic regression method could significantly improve HIV testing efficiency among children presenting to malnutrition, inpatient, and OVC entry points in Ethiopia while maintaining case identification. These tools are simplified to practically implement and can potentially be validated for use at various entry points. HIV programs in low-prevalence countries can also further investigate and optimize these tools in their settings. |
Enhancing and promoting data management and systematic monitoring for an improved HIV/AIDS programs in Addis Ababa, Ethiopia
Habte D , Zemenfeskudus S , Endale M , Zeidan M , Getachew D , Woldemichael D , Wesene AS , Teklebirhan E , Eyayu F , Zewdie R , Yirga D , Amdino W , Melaku Z , Abayneh SA . BMC Health Serv Res 2022 22 (1) 43 Background: Ethiopia Population-based HIV Impact Assessment findings showed that in Addis Ababa, only 65.2% of people living with HIV (PLHIV) know their status. We present the enhanced HIV/AIDS data management and systematic monitoring experience in Addis Ababa City Administration Health Bureau (AACAHB). Methods: AACAHB established a command-post with leadership and technical team members from the health bureau, 10 sub-city health offices, and non-governmental stakeholders. The command-post improved governance, standardized HIV program implementation, and established accountability mechanism. A web-based database was established at each health facility, sub-city, and AACAHB level. Performance was scored (green, ≥75%; yellow, 50–74%; red, < 50%). The command-post reviewed performance on weekly basis. A mentorship team provided a weekly site-level support at underperforming public and private health facilities. At facility level, quality of data on recording tools such as registers, and individual medical records were maintained through continued review, feedback mechanisms and regular consistency check of data. Percentage and 95% confidence interval were computed to compare the improvement in program performance over time. Results: After 6 months of intervention period, the monthly New HIV case finding in 47 health facilities increased from 422 to 734 (1.7 times) and treatment initiation increased from 302 to 616 (2 times). After 6 months, the aggregate scoring for HIV testing at city level improved from yellow to green, HIV case finding improved from red to green, and treatment initiation improved from red to yellow. An increasing trend was noted in HIV positive case finding with statistically significant improvement from 43.4% [95% Confidence Interval: 40.23–46.59%] in May 2019 to 74.9% [95% Confidence Interval: 72.03–77.6%] in September 2019. Similarly, significant improvement was recorded for new HIV treatment from 30.9% [95% Confidence Interval: 28.01–33.94%] in May 2019 to 62.5% [95% Confidence Interval: 59.38–65.6%] in September 2019. Conclusions: Regular data driven HIV program review was institutionalized at city, sub-city and health facility levels which further improved HIV program monitoring and performance. The performance of HIV case finding and treatment initiation improved significantly via using intensified monitoring, data driven performance review, targeted site-level support based on the gap, and standardized approaches. © 2022, The Author(s). |
Finding children living with HIV in low-prevalence countries: HIV prevalence and testing yield from 5 entry points in Ethiopia
Hrapcak S , Bekele A , Ahmed J , Ayalew J , Gutreuter S , Kumssa H , Antefe T , Mengistu S , Mirkovic K , Dziuban EJ , Ross C , Belay Z , Tilahun T , Kassa D , Teferi W . Pediatr Infect Dis J 2021 40 (12) 1090-1095 BACKGROUND: Limited data in low HIV prevalence settings such as Ethiopia limit policy development and implementation of optimized pediatric testing approaches to close the treatment gap. This study aimed to determine HIV prevalence, testing yield and factors associated with HIV among children at 5 entry points. METHODS: We conducted a cross-sectional study from May 2017 to March 2018 in 29 public health facilities in Amhara and Addis Ababa regions in Ethiopia. Children 2-14 years were enrolled through 5 entry points. Data were obtained from registers, medical records and interviews with caregivers. HIV prevalence and testing yields were calculated for each entry point. Mixed-effects logistic regression analysis identified factors associated with undiagnosed HIV. RESULTS: The study enrolled 2166 children, of whom 94 were HIV positive (40 newly diagnosed). HIV prevalence and testing yield were the highest among children of HIV-positive adults (index testing; 8.2% and 8.2%, respectively) and children presenting to tuberculosis clinics (7.9% and 1.8%) or with severe malnutrition (6.5% and 1.4%). Factors associated with undiagnosed HIV included tuberculosis or index entry point [adjusted odds ratio (aOR), 11.97; 95% CI 5.06-28.36], deceased mother (aOR 4.55; 95% CI 1.30-15.92), recurrent skin problems (aOR 17.71; 95% CI 7.75-40.43), severe malnutrition (aOR 4.56; 95% CI 2.04-10.19) and urban residence (aOR 3.47; 95% CI 1.03-11.66). CONCLUSIONS: Index testing is a critical strategy for pediatric case finding in Ethiopia. Strategies and resources can prioritize minimizing missed opportunities in implementing universal testing for very sick children (tuberculosis, severe malnutrition) and implementing targeted testing in other entry points through use of factors associated with HIV. |
Laboratory development and pilot-scale deployment of a two-part foamed rock dust
Brown CB , Perera IE , Harris ML , Chasko LL , Addis JD , Klima S . J Loss Prev Process Ind 2022 74 U.S. Code of Federal Regulations 30 CFR 75.402 and 75.403 require 80% total incombustible content to be maintained within 40 feet of the coal mine face via the liberal application of rock dust. Unfortunately, this application of rock dust limits miners' visibility downwind and can increase the miners' exposures to a respirable nuisance dust. Wet rock dust applied as a slurry is, at times, used to negate these negative effects. Although this aids in meeting the total incombustible limits, the slurry forms a hard cake when dried and no longer effectively disperses as needed to suppress a coal dust explosion. As a result, a dry rock dust must be reapplied to maintain a dispersible layer. Therefore, researchers from the National Institute for Occupational Safety and Health (NIOSH) have been working towards finding and testing a foamed rock dust formulation that can be applied wet on mine surfaces and remain dispersible once dried which minimizes the likelihood of mine disasters, including mine explosions. The initial tests were aimed at discerning dispersion characteristics of three different foamed rock dusts via the NIOSH-developed dispersion chamber and led to identification of a two-part foam with adequate dispersion characteristics. The current study was conducted to assess the robustness of the two-part foamed rock dust. Through a series of laboratory-scale experiments using the dispersibility chamber, the effects of testing conditions and product formulations on the foam's dispersibility was determined. Some of the tested variables include: exposing the foam to high humidity, varying the component levels of the foamed rock dust, altering the rock dust size distribution, and varying the rock dust types. Further pilot-scale tests examined the atmospheric concentrations of dust via personal dust monitors downwind of foamed rock dust production and application. Additionally, product consistency was recorded during pilot-scale testing at key points in the formulation and application. The results of these experiments will be discussed in this paper. © 2021 |
Seroprevalence and risk factors for SARS-CoV-2 Infection in selected urban areas in Ethiopia: a cross-sectional evaluation during July 2020.
Tadesse EB , Endris AA , Solomon H , Alayu M , Kebede A , Eshetu K , Teka G , Seid BE , Ahmed J , Abayneh SA , Moges B , Gerawork H , Sugerman D , Assefa Z , Abayneh A , Abate E , Taddese L . Int J Infect Dis 2021 111 179-185 BACKGROUND: Ethiopia reported the first case of COVID-19 on 13(th) March, 2020 with community transmission ensuing by mid-May. A national, population-based serosurvey against anti-SARS-CoV-2 IgG was conducted to measure the prevalence of prior COVID-19 infections and better approximate the burden across major towns in Ethiopia. METHODS: We conducted a cross-sectional, population-based serosurvey from June 24 to July 8, 2020 in 14 major urban areas. Two-stage cluster sampling was used to randomly select enumeration areas and households. All persons aged ≥15 years were enrolled. Serum samples were tested by Abbott™ ARCHITECT™ assay for SARS-CoV-2 IgG antibodies. National COVID-19 surveillance data on the median date of the serosurvey is analyzed for comparison. FINDINGS: Adjusted seroprevalence was 3.5% (95% CI: 3.2%-3.8%) after controlling for age, sex and test kit performance. Males (3.7%) and females (3.3%) were nearly equally infected, while middle-aged adults '40-65 years' had the highest (4.0%) prevalence. Gambella (7.5%), Dire Dawa (6.2%) and Jigjiga (6.1%) were the most affected towns. About 6.7% and 8.0% of seropositives had symptoms and chronic underlying illness, respectively. A surveillance system had identified 4,416 RT-PCR confirmed cases in Addis Ababa. INTERPRETATION: This serosurvey shows that a majority of urban Ethiopians remain uninfected with SARS-CoV-2. Most anti-SARS-CoV-2 IgG positive cases were asymptomatic with no underlying illness, keeping case detection to a minimum. |
Factors associated with unawareness of HIV-positive status in urban Ethiopia: Evidence from the Ethiopia population-based HIV impact assessment 2017-2018
Lulseged S , Belete W , Ahmed J , Gelibo T , Teklie H , West CW , Melaku Z , Demissie M , Farhani M , Eshetu F , Birhanu S , Getaneh Y , Patel H , Voetsch AC . PLoS One 2021 16 (8) e0255163 BACKGROUND: The HIV epidemic in Ethiopia is concentrated in urban areas. Ethiopia conducted a Population-based HIV Impact Assessment (EPHIA) in urban areas between October 2017 and April 2018 to measure the status of the country's response to the epidemic. METHODS: We conducted field data collection and HIV testing in randomly selected households using the national, rapid testing algorithm with laboratory confirmation of seropositive samples using a supplemental assay. In addition to self-report on HIV diagnosis and treatment, all HIV-positive participants were screened for a set of HIV antiretroviral (ARV) drugs indicative of the first- and second-line regimens. We calculated weighted frequencies and 95% confidence intervals to assess regional variation in participants' level of unawareness of their HIV-positive status (adjusted for ARV status). RESULTS: We interviewed 20,170 survey participants 15-64 years of age, of which 19,136 (95%) were tested for HIV, 614 (3.2%) tested positive, and 119 (21%) of HIV-positive persons were unaware of their HIV status. Progress towards the UNAIDS first 90 target (90% of people living with HIV would be aware of their HIV status by 2020) substantially differed by administrative region of the country. In the bivariate analysis using log binomial regression, three regions (Oromia, Addis Ababa, and Harari), male gender, and young age (15-24 years) were significantly associated with awareness of HIV positive status. In multivariate analysis, the same variables were associated with awareness of HIV-positive status. CONCLUSION: One-fifth of the HIV-positive urban population were unaware of their HIV-positive status. The number of unaware HIV-positive individuals has a different distribution than the HIV prevalence. National and regional planning and monitoring activities could address this potentially substantial source of undetected HIV infection by increasing HIV testing among young people, men and individuals who do not use condoms. |
Barriers and opportunities for canine rabies vaccination campaigns in Addis Ababa, Ethiopia
Yoak AJ , Haile A , O'Quin J , Belu M , Birhane M , Bekele M , Murphy S , Medley A , Vincent E , Stewart D , Shiferaw ML , Tafese K , Garabed R , Pieracci EG . Prev Vet Med 2021 187 105256 BACKGROUND: Canine rabies is endemic in Ethiopia and presents a significant burden for both animal and human health. We investigate barriers to dog vaccination in Addis Ababa, Ethiopia. These results can be utilized to improve and target future rabies control efforts. METHODOLOGY/PRINCIPLE FINDINGS: During May of 2017, dog owners were surveyed during a free canine rabies vaccination programs that utilized both door-to-door (DtD) and central point (CP) vaccination methods. Surveys collected information on preferences for rabies vaccine delivery and were administered in Amharic. A total of 1057 surveys were completed. Of those surveyed, 62.4 % indicated that their dogs had been vaccinated against rabies within the last year. Commonly reported barriers to vaccination were a lack of awareness that dogs required rabies vaccines (18.1 %) and lack of knowledge about where to find vaccine (15.0 %). The median price owners were willing to pay for vaccination was 25 birr ($0.91 USD) and the median distance willing to travel was 1.0 km; however, 48.9 % of those surveyed during DtD were unwilling to travel at all. We identified 3 classes of respondents who were grouped due to their responses by latent class analysis: 'the Unaware', 'the Vaccinators', and 'the Multiple Barriers'. CONCLUSIONS/SIGNIFICANCE: Although many respondents were willing to pay for rabies vaccine (94.0 %); the preferred cost (median) was less than the actual cost of providing the vaccine. This supports the need for reduced-cost or free vaccine to achieve and sustain the 70 % vaccine coverage target threshold for canine rabies elimination. Additionally, a significant portion (41.5 %) of those surveyed indicated that they were unwilling to travel in order to have their dog vaccinated. The latent class analysis provides useful guidance on how to reach target vaccination. Owners from 'the Unaware' group made up 18.1 % of respondents and their high rate of allowing their dogs to roam identifies them as a prime target for canine health and behavior education. 'The Multiple Barriers' owners reported lower degrees of dog roaming and were substantially more likely to be found by DtD campaigns, possibly because they have limited ability/interest in handling their dogs. These results demonstrate the importance of incorporating DtD vaccination as well as subsidies to maximize vaccine coverage in Addis Ababa. |
Bacteriologically-confirmed pulmonary tuberculosis in an Ethiopian prison: Prevalence from screening of entrant and resident prisoners
Tsegaye Sahle E , Blumenthal J , Jain S , Sun S , Young J , Manyazewal T , Woldeamanuel H , Teferra L , Feleke B , Vandenberg O , Rey Z , Briggs-Hagen M , Haubrich R , Amogne W , McCutchan JA . PLoS One 2019 14 (12) e0226160 BACKGROUND: Pulmonary Tuberculosis (PTB) is a major health problem in prisons. Multiple studies of TB in regional Ethiopian prisons have assessed prevalence and risk factors but have not examined recently implemented screening programs for TB in prisons. This study compares bacteriologically-confirmed PTB (BC-PTB) prevalence in prison entrants versus residents and identifies risk factors for PTB in Kality prison, a large federal Ethiopian prison located in Addis Ababa, through a study of an enhanced TB screening program. METHODS: Participating prisoners (n = 13,803) consisted of 8,228 entrants screened continuously and 5,575 residents screened in two cross-sectional waves for PTB symptoms, demographics, TB risk factors, and medical history. Participants reporting at least one symptom of PTB were asked to produce sputum which was examined by microscopy for acid-fast bacilli, Xpert MTB/RIF assay and MGIT liquid culture. Prevalence of BC-PTB, defined as evidence of Mycobacterium tuberculosis (MTB) in sputum by the above methods, was compared in entrants and residents for the study. Descriptive analysis of prevalence was followed by bivariate and multivariate analyses of risk factors. RESULTS: Prisoners were mainly male (86%), young (median age 26 years) and literate (89%). Prevalence of TB symptoms by screening was 17% (2,334/13,803) with rates in residents >5-fold higher than entrants. Prevalence of BC-PTB detected by screening in participating prisoners was 0.16% (22/13,803). Prevalence in residents increased in the second resident screening compared to the first (R1 = 0.10% and R2 = 0.39%, p = 0.027), but remained higher than in entrants (4.3-fold higher during R1 and 3.1-fold higher during R2). Drug resistance (DR) was found in 38% (5/13) of culture-isolated MTB. Risk factors including being ever diagnosed with TB, history of TB contact and low Body Mass Index (BMI) (<18.5) were significantly associated with BC-PTB (p<0.05). CONCLUSIONS: BC-PTB prevalence was strikingly lower than previously reported from other Ethiopian prisons. PTB appears to be transmitted within this prison based on its higher prevalence in residents than in entrants. Whether a sustained program of PTB screening of entrants and/or residents reduces prevalence of PTB in prisons is not clear from this study, but our findings suggest that resources should be prioritized to resident, rather than entrant, screening due to higher BC-PTB prevalence. Detection of multi- and mono-DR TB in both entrant and resident prisoners warrants regular screening for active TB and adoption of methods to detect drug resistance. |
Face ventilation on a bleederless longwall panel
Schatzel SJ , Gangrade V , Addis JD , Hollerich CA , Chasko LL . Min Metall Explor 2019 36 (3) 531-539 A ventilation study using tracer gas was conducted at a western US coal mine. The objective of the study was to evaluate the movement of longwall face air exchanges between the face and worked-out area and to document the presence or absence of face airflow pathways between these locations. The mine operator uses a bleederless longwall ventilation system with a back return and a blowing mine ventilation system. The study was conducted on an active panel and included both underground and surface monitoring sites. The study used sulfur hexafluoride (SF6) released as a slug on the longwall face and in the front of the gob inby the face. The velocity of the tracer gas movement in the gob was 0.019 m/s (3.7 fpm). The rate of movement for the overall tracer gas slug averaged about 0.0091 m/s (1.8 fpm). A separate tracer gas test initiated with the release of SF6 into the legs of the first shield showed the existence of more than one pathway of face air in the general direction from the headgate towards the tailgate corner. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob. A more detailed characterization of longwall system air and gas movement allows a mine to better assess its ventilation design for controlling gas on the face and in the gob. |
Investigating the impact of caving on longwall mine ventilation using scaled physical modeling
Gangrade V , Schatzel SJ , Harteis SP , Addis JD . Min Metall Explor 2019 36 (4) 729-740 In longwall mining, ventilation is considered one of the more effective means for controlling gases and dust. In order to study longwall ventilation in a controlled environment, researchers built a unique physical model called the Longwall Instrumented Aerodynamic Model (LIAM) in a laboratory at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) campus. LIAM is a 1:30 scale physical model geometrically designed to simulate a single longwall panel with a three-entry headgate and tailgate configuration, along with three back bleeder entries. It consists of a twopart heterogeneous gob that simulates a less compacted unconsolidated zone and more compacted consolidated zone. It has a footprint of 8.94 m (29 ft.) by 4.88 m (16 ft.), with a simulated face length of 220 m (720 ft.) in full scale. LIAM is built with critical details of the face, gob, and mining machinery. It is instrumented with pressure gauges, flow anemometers, temperature probes, a fan, and a data acquisition system. Scaling relationships are derived on the basis of Reynolds and Richardson numbers to preserve the physical and dynamic similitude. This paper discusses the findings from a study conducted in the LIAM to investigate the gob-face interaction, airflow patterns within the gob, and airflow dynamics on the face for varying roof caving characteristics. Results are discussed to show the impact of caving behind the shields on longwall ventilation. |
Epidemiology of measles in the metropolitan setting, Addis Ababa, Ethiopia, 2005-2014: a retrospective descriptive surveillance data analysis
Hassen MN , Woyessa AB , Getahun M , Beyene B , Buluanger L , Ademe A , Bekele A , Addissie A , Kebede A , Jima D . BMC Infect Dis 2018 18 (1) 400 BACKGROUND: Measles is a highly infectious and serious respiratory viral disease which caused by a virus. It is a significant cause of illness and death worldwide. This data analysis was conducted to describe the trend and determine the reporting rate of measles cases in Addis Ababa to make recommendation for the government of the city to strengthening measles control interventions. METHODS: We obtained and extracted ten years (2005-2014) Addis Ababa city's measles surveillance data from national database. We carried out retrospective descriptive data analysis by time, place and person variables. We calculated cumulative and specific reporting rates by dividing measles cases (lab confirmed, epidemiologically linked and compatible cases) to respective population and multiplying by 100,000. We divided average of ten years measles cases to midyear population and multiplied by 100,000 to calculate annualized reporting rate. We analyzed non-measles febrile rash rate by dividing laboratory negative cases to total population and multiplying by 100,000. RESULTS: A total of 4203 suspected measles cases were identified. Among them 1154 (27.5%) were laboratory confirmed, 512 (12.2%) were clinically compatible, 52 (1.2%) were epidemiologically linked cases and the rest 2485 (59.1%) were IgM negative for measles which makes total measles cases 1718 (40.9%). Median age was 5 years with 2-18 years interquartile-range. The annualized measles reporting rate was 5.9, which was 40.2 among > 1 year, 11.5 among 1-4 years, 6.0 among 5-14 years, 4.1 among 15-44 years and 0.01 among >/= 45 years per 100,000 population. Among the total measles cases; 380 (22%) were received at least one dose of measles containing vaccine (MCV) while 415 (24%) cases were not vaccinated and the vaccination status of 923 (54%) cases were not known. CONCLUSION: Our analysis revealed that the reporting rate was higher among young children than older age group. Among all the patients 22% were received at least one dose of measles vaccine whereas 13% were not vaccinated against measles antigen. Routine immunization should be strengthened to reach all children through well monitored vaccine cold chain management. |
Evaluation of fiber optic methane sensor using a smoke chamber
Li M , Dubaniewicz T , Dougherty H , Addis J . Int J Min Sci Technol 2018 28 (6) 969-974 This report presents the results of experiments to evaluate a prototype fiber optic methane monitor exposed to smoke using a smoke chamber to simulate atmospheric conditions in an underground coal mine after a fire or explosion. The experiments were conducted using test fires of different combustible sources commonly found in mines —douglas-fir wood, SBR belt, and Pittsburgh seam coal. The experiments were designed to assess the response of the fiber optic methane sensor to different contaminants, different contaminant levels and different contaminant durations produced from the test fires. Since the prototype methane monitor detects methane by measuring absorption at a specific wavelength, optical power at the absorption wavelength (1650 nm) was measured as a function of smoke concentration and duration. The other sensor response parameter-methane response times-were measured between smoke tests to assess the impact of soot accumulation on the sensor. Results indicate that the sensor screen effectively prevented smoke from obscuring the optical beam within the sensor head, with minimal impact on the system optical power budget. Methane response times increased with smoke exposure duration, attributed to soot loading on the protective screen. |
The single-visit approach as a cervical cancer prevention strategy among women with HIV in Ethiopia: successes and lessons learned
Shiferaw N , Salvador-Davila G , Kassahun K , Brooks MI , Weldegebreal T , Tilahun Y , Zerihun H , Nigatu T , Lulu K , Ahmed I , Blumenthal PD , Asnake M . Glob Health Sci Pract 2016 4 (1) 87-98 INTRODUCTION: Cervical cancer is the second most common form of cancer for women in Ethiopia. Using a single-visit approach to prevent cervical cancer, the Addis Tesfa (New Hope) project in Ethiopia tested women with HIV through visual inspection of the cervix with acetic acid wash (VIA) and, if tests results were positive, offered immediate cryotherapy of the precancerous lesion or referral for loop electrosurgical excision procedure (LEEP). The objective of this article is to review screening and treatment outcomes over nearly 4 years of project implementation and to identify lessons learned to improve cervical cancer prevention programs in Ethiopia and other resource-constrained settings. METHODS: We analyzed aggregate client data from August 2010 to March 2014 to obtain the number of women with HIV who were counseled, screened, and treated, as well as the number of annual follow-up visits made, from the 14 tertiary- and secondary-level health facilities implementing the single-visit approach. A health facility assessment (HFA) was also implemented from August to December 2013 to examine the effects of the single-visit approach on client flow, staff workload, and facility infrastructure 3 years after initiating the approach. RESULTS: Almost all (99%) of the 16,632 women with HIV counseled about the single-visit approach were screened with VIA during the study period; 1,656 (10%) of them tested VIA positive (VIA+) for precancerous lesions. Among those who tested VIA+ and were thus eligible for cryotherapy, 1,481 (97%) received cryotherapy treatment, but only 80 (63%) women eligible for LEEP actually received the treatment. The HFA results showed frequent staff turnover, some shortage of essential supplies, and rooms that were judged by providers to be too small for delivery of cervical cancer prevention services. CONCLUSION: The high proportions of VIA screening and cryotherapy treatment in the Addis Tesfa project suggest high acceptance of such services by women with HIV and feasibility of implementation in secondary- and tertiary-level health facilities. However, success of cervical cancer prevention programming must address wider health system challenges to ensure sustainability and appropriate scale-up to the general population of Ethiopia and other resource-constrained settings. |
Improved specimen-referral system and increased access to quality laboratory services in Ethiopia: The role of the public-private partnership
Kebede Y , Fonjungo PN , Tibesso G , Shrivastava R , Nkengasong JN , Kenyon T , Kebede A , Gadde R , Ayana G . J Infect Dis 2016 213 Suppl 2 S59-64 BACKGROUND: Nonstandardized specimen-transport logistics, lack of laboratory personnel to transport specimens, lack of standard specimen containers, and long turnaround time (TAT) hindered access to quality laboratory services. The objective of the Becton, Dickinson, and Company (BD)-US President's Emergency Plan for AIDS Relief (PEPFAR) Public-Private Partnership (PPP) was to support country-specific programs to develop integrated laboratory systems, services, and quality improvement strategies, with an emphasis on strengthening the specimen-referral system (SRS). METHODS: In 2007, through the Centers for Disease Control and Prevention (CDC), the Ethiopian Public Health Institute (EPHI) joined with the BD-PEPFAR PPP to strengthen laboratory systems. A joint planning and assessment committee identified gaps in the SRS for prioritization and intervention and piloted the system in Addis Ababa and Amhara Region. RESULTS: The PPP established standardized, streamlined specimen logistics, using the Ethiopian Postal Service Enterprise to support a laboratory network in which 554 facilities referred specimens to 160 laboratories. The PPP supported procuring 400 standard specimen containers and the training of 586 laboratory personnel and 81 postal workers. The average TAT was reduced from 7 days (range, 2-14 days) to 2 days (range, 1-3 days) in Addis Ababa and from 10 days (range, 6-21 days) to 5 days (range, 2-6 days) in Amhara Region. CONCLUSIONS: This study highlights the feasibility and untapped potential of PPPs to strengthen laboratory systems. This planned and structured approach to improving specimen referral enhanced access to quality laboratory services. |
Metals exposures of residents living near the Akaki river in Addis Ababa, Ethiopia: A cross-sectional study
Yard E , Bayleyegn T , Abebe A , Mekonnen A , Murphy M , Caldwell KL , Luce R , Hunt DR , Tesfaye K , Abate M , Assefa T , Abera F , Habte K , Chala F , Lewis L , Kebede A . J Environ Public Health 2015 2015 935297 BACKGROUND: The Akaki River in Ethiopia has been found to contain elevated levels of several metals. Our objectives were to characterize metals exposures of residents living near the Akaki River and to assess metal levels in their drinking water. METHODS: In 2011, we conducted a cross-sectional study of 101 households in Akaki-Kality subcity (near the Akaki River) and 50 households in Yeka subcity (distant to the Akaki River). One willing adult in each household provided urine, blood, and drinking water sample. RESULTS: Urinary molybdenum (p < 0.001), tungsten (p < 0.001), lead (p < 0.001), uranium (p < 0.001), and mercury (p = 0.049) were higher in Akaki-Kality participants compared to Yeka participants. Participants in both subcities had low urinary iodine; 45% met the World Health Organization (WHO) classification for being at risk of moderate iodine deficiency. In Yeka, 47% of households exceeded the WHO aesthetic-based reference value for manganese; in Akaki-Kality, only 2% of households exceeded this value (p < 0.001). There was no correlation between metals levels in water samples and clinical specimens. CONCLUSIONS: Most of the exposures found during this investigation seem unlikely to cause acute health effects based on known toxic thresholds. However, toxicity data for many of these metals are very limited. |
Notes from the field: hepatitis E outbreak among refugees from South Sudan - Gambella, Ethiopia, April 2014-January 2015
Browne LB , Menkir Z , Kahi V , Maina G , Asnakew S , Tubman M , Elyas HZ , Nigatu A , Dak D , Maung UA , Nakao JH , Bilukha O , Shahpar C . MMWR Morb Mortal Wkly Rep 2015 64 (19) 537 In early April 2014, two South Sudanese refugees in the Gambella region of western Ethiopia experienced acute onset of jaundice, accompanied by fever. One patient was a pregnant woman aged 24 years evaluated at a routine prenatal clinic visit in Leitchour refugee camp. The second patient was a malnourished boy aged 1 year who resided in Tierkidi refugee camp. The boy died despite hospitalization. During the last 2 weeks of May, four more cases of acute jaundice syndrome (AJS), defined as yellow discoloration of the eyes, were detected in Leitchuor. By mid-June, an additional 50 AJS cases were reported across three large camps in the region, Kule, Leitchuor, and Tierkidi, with 45 (90%) of these cases reported in Leitchuor. Sera collected from a convenience sample of 21 AJS cases were sent to Addis Ababa and Nairobi for real-time polymerase chain reaction testing; 12 (57%) were positive for hepatitis E virus (HEV) RNA. By January 2015, a total of 1,117 suspected cases of hepatitis E meeting the case definition of AJS were reported among refugees in camps across Gambella. |
The Global One Health paradigm: challenges and opportunities for tackling infectious diseases at the human, animal, and environment interface in low-resource settings
Gebreyes WA , Dupouy-Camet J , Newport MJ , Oliveira CJ , Schlesinger LS , Saif YM , Kariuki S , Saif LJ , Saville W , Wittum T , Hoet A , Quessy S , Kazwala R , Tekola B , Shryock T , Bisesi M , Patchanee P , Boonmar S , King LJ . PLoS Negl Trop Dis 2014 8 (11) e3257 Zoonotic infectious diseases have been an important concern to humankind for more than 10,000 years. Today, approximately 75% of newly emerging infectious diseases (EIDs) are zoonoses that result from various anthropogenic, genetic, ecologic, socioeconomic, and climatic factors. These interrelated driving forces make it difficult to predict and to prevent zoonotic EIDs. Although significant improvements in environmental and medical surveillance, clinical diagnostic methods, and medical practices have been achieved in the recent years, zoonotic EIDs remain a major global concern, and such threats are expanding, especially in less developed regions. The current Ebola epidemic in West Africa is an extreme stark reminder of the role animal reservoirs play in public health and reinforces the urgent need for globally operationalizing a One Health approach. The complex nature of zoonotic diseases and the limited resources in developing countries are a reminder that the need for implementation of Global One Health in low-resource settings is crucial. The Veterinary Public Health and Biotechnology (VPH-Biotec) Global Consortium launched the International Congress on Pathogens at the Human-Animal Interface (ICOPHAI) in order to address important challenges and needs for capacity building. The inaugural ICOPHAI (Addis Ababa, Ethiopia, 2011) and the second congress (Porto de Galinhas, Brazil, 2013) were unique opportunities to share and discuss issues related to zoonotic infectious diseases worldwide. In addition to strong scientific reports in eight thematic areas that necessitate One Health implementation, the congress identified four key capacity-building needs: (1) development of adequate science-based risk management policies, (2) skilled-personnel capacity building, (3) accredited veterinary and public health diagnostic laboratories with a shared database, and (4) improved use of existing natural resources and implementation. The aim of this review is to highlight advances in key zoonotic disease areas and the One Health capacity needs. |
An investigation into the seroprevalence of Toxoplasma gondii, Bartonella spp., feline immunodeficiency virus (FIV), and feline leukaemia virus (FeLV) in cats in Addis Ababa, Ethiopia
Tiao N , Darrington C , Molla B , Saville WJ , Tilahun G , Kwok OC , Gebreyes WA , Lappin MR , Jones JL , Dubey JP . Epidemiol Infect 2013 141 (5) 1029-33 Toxoplasma gondii and Bartonella spp. are zoonotic pathogens of cats. Feline immunodeficiency virus (FIV), and feline leukaemia virus (FeLV) are immunosuppressive viruses of cats that can affect T. gondii oocyst shedding. In this study, the prevalence of antibodies to T. gondii, Bartonella spp., FIV, as well as FeLV antigens were determined in sera from feral cats (Felis catus) from Addis Ababa, Ethiopia. Using the modified agglutination test, IgG antibodies to T. gondii were found in 41 (85.4%) of the 48 cats with titres of 1:25 in one, 1:50 in one, 1:200 in six, 1:400 in six, 1:800 in six, 1:1600 in eight, and 1:3200 in 13 cats. Toxoplasma gondii IgM antibodies were found in 11/46 cats tested by ELISA, suggesting recent infection. Antibodies to Bartonella spp. were found in five (11%) of 46 cats tested. Antibodies to FIV or FeLV antigen were not detected in any of the 41 cats tested. The results indicate a high prevalence of T. gondii and a low prevalence of Bartonella spp. infection in cats in Ethiopia. |
Challenges of establishing routine influenza sentinel surveillance in Ethiopia, 2008-2010
Ayele W , Demissie G , Kassa W , Zemelak E , Afework A , Amare B , Cox CM , Jima D . J Infect Dis 2012 206 Suppl 1 S41-5 Ethiopia launched influenza surveillance in November 2008. By October 2010, 176 patients evaluated at 5 sentinel health facilities in Addis Ababa met case definitions for influenza-like illness or severe acute respiratory illness (SARI). Most patients (131 [74%]) were children aged 0-4 years. Twelve patients (7%) were positive for influenza virus. Most patients (109 [93%]) were aged <5 years, of whom only 3 (2.8%) had laboratory-confirmed influenza. Low awareness of influenza by healthcare workers, misperceptions regarding case definitions, and insufficient human resources at sites could have potentially led to many missed cases, resulting in suboptimal surveillance. |
Detonability of natural gas-air mixtures
Gamezo VN , Zipf Jr RK , Sapko MJ , Marchewka WP , Mohamed KM , Oran ES , Kessler DA , Weiss ES , Addis JD , Karnack FA , Sellers DD . Combust Flame 2011 159 (2) 870-881 Direct initiation experiments were carried out in a 105 cm diameter tube to study detonation properties and evaluate the detonability limits for mixtures of natural gas (NG) with air. The natural gas was primarily methane with 1.5–1.7% of ethane. A stoichiometric methane–oxygen mixture contained in a large plastic bag was used as a detonation initiator. Self-supporting detonations with velocities and pressures close to theoretical CJ values were observed in NG–air mixtures containing from 5.3% to 15.6% of NG at atmospheric pressure. These detonability limits are wider than previously measured in smaller channels, and close to the flammability limits. Detonation cell patterns recorded near the limits vary from large cells of the size of the tube to spiral traces of spin detonations. Away from the limits, detonation cell sizes decrease to about 20 cm for 10% NG, and are consistent with existing data for methane–air mixtures obtained in smaller channels. Observed cell patterns are very irregular, and contain secondary cell structures inside primary cells and fine structures inside spin traces. |
Methane-air detonation experiments at NIOSH Lake Lynn Laboratory
Zipf Jr RK , Gamezo VN , Sapko MJ , Marchewka WP , Mohamed KM , Oran ES , Kessler DA , Weiss ES , Addis JD , Karnack FA , Sellers DD . J Loss Prev Process Ind 2011 26 (2) 295-301 The methane-air detonation experiments are performed to characterize high pressure explosion processes that may occur in sealed areas of underground coal mines. The detonation tube used for these studies is 73m long, 105cm internal diameter, and closed at one end. The test gas is 97.5% methane with about 1.5% ethane, and the methane-air test mixtures varied between 4% and 19% methane by volume. Detonations were successfully initiated for mixtures containing between 5.3% and 15.5% methane. The detonations propagated with an average velocity between 1512 and 1863m/s. Average overpressures recorded behind the first shock pressure peak varied between 1.2 and 1.7MPa. The measured detonation velocities and pressures are close to their corresponding theoretical Chapman-Jouguet (CJ) detonation velocity (DCJ) and detonation pressure (PCJ). Outside of these detonability limits, failed detonations produced decaying detached shocks and flames propagating with velocities of approximately 1/2 DCJ. Cell patterns on smokefoils during detonations were very irregular and showed secondary cell structures inside primary cells. The measured width of primary cells varied between 20cm near the stoichiometry and 105cm (tube diameter) near the limits. The largest detonation cell (105cm wide and 170cm long) was recorded for the mixture containing 15.3% methane. |
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