Research Articles (Statistics)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1835

A collection containing some of the full text peer-reviewed/ refereed articles published by researchers from
the Department of Statistics

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Spatiotemporal models with confounding effects : application on under-five mortality across four sub-Saharan African countries
(Frontiers Media, 2025-01) Fenta, Haile Mekonnen; Chen, Ding-Geng (Din); Zewotir, Temesgen T.; Rad, Najmeh Nakhaei
BACKGROUND : Different strategies have been developed to minimize under-five mortality (U5M) in sub-Saharan African (sSA) countries; however, it is still a major health concern for children in the region. Spatiotemporal modeling is important for areal data collected over time. However, when the number of time points and spatial areas is large and the areas are disconnected, fitting the model becomes computationally complex because of the high number of required parameters to be estimated. Therefore, the main aim of this study is to adopt a spatiotemporal dynamic model that includes the confounding effects between time, space, and their interactions with fixed covariates, with a special emphasis on U5M across disconnected sSA countries. METHOD : We used nationally publicly representative Demographic and Health Survey (DHS) data for the period from 2000 to 2020. Bayesian spatiotemporal hierarchical modeling with an integrated nested Laplace approximation (INLA) program was used to model the spatiotemporal distribution of U5M among children across 37 districts located in four disconnected sSA regions: Ethiopia, Nigeria, Zimbabwe, and Ghana. RESULTS : A total of 170,356 under-five children from 37 districts were considered, and 15,467 died before the age of five. The relative risk of U5M in the first DHS was 2.02, which sharply decreased to 0.5 in the recent phase. The proportion of improved access to water, sanitation, clean fuel use, urbanization, and access to health facilities in the district had a significant negative association with U5M. The higher the proportion of these covariates, the lower is the prevalence of childhood mortality. CONCLUSION : This study revealed evidence of strong spatial, temporal, and interaction effects that influence under-five mortality risk across districts. Improving the women’s literacy index, access to improved water, the use of clean fuel, and the wealth index are associated with an improvement in the risk of mortality among under-five children across the districts. Districts in Nigeria and Ethiopia have the highest risk of U5M; hence, districts in these countries require special attention.
Determinants of community-acquired pneumonia among under-five children in Awi Zone, Northwest Ethiopia
(Frontiers Media, 2025-05) Birhan, Nigussie Adam; Workineh, Alene Yirsaw; Wolde, Zelalem Meraf; Abich, Emebiet; Alemayehu, Gedif Mulat; Nigussie, Atalaye; Alemu, Yenew; Messfin, Chalachew Alemi; Belay, Denekew Bitew
BACKGROUND : Globally, community-acquired pneumonia is the leading cause of death in under-five children, accounting for 7.6 million deaths. Among these deaths, approximately 99% occur in low and middle-income countries. The present study aimed to assess the magnitude of community-acquired pneumonia and its associated factors among under-five children in Awi Zone. METHODS : A community cross-sectional study was conducted on 1,368 participants from March to July 2023. A multistage sampling method was used. Data were entered into Epi-Data and exported to STATA for analysis. Bivariable and multivariable logistic regressions were used. Variables with a p-value of < 0.05 were considered statistically significant. RESULTS : The percentage of community-acquired pneumonia among under-five children was 11.33% (95% CI: 9.75-13.12%). Primary education [AOR = 0.38; 95% CI:0.15, 0.95], stunting [AOR = 4.80; 95% CI: 2.31, 9.94], diarrhea [AOR = 3.75; 95% CI: 1.96, 7.18], acute lower respiratory tract infection [AOR = 14.57, 95% CI: 3.18, 66.78], acute upper respiratory tract infection [AOR = 9.06; 95% CI: 2.03, 40.42], and presence of separate kitchen [AOR = 0.38, 95% CI: 0.20, 0.72] were associated with community-acquired pneumonia. CONCLUSION : In this study, the percentage of community-acquired pneumonia was relatively high. Hence, we recommend adequate health education in areas such as nutritional intervention, the prevention and early treatment of diarrhea and acute respiratory tract infections (ARTI), and preventing indoor air pollution to reduce the risk of community-acquired pneumonia.
Determinants of child malnutrition and morbidity in Ethiopia : a structural equation modeling approach
(Frontiers Media, 2025-04) Warssamo, Birhanu Betela; Belay, Denekew Bitew; Chen, Ding-Geng (Din)
BACKGROUND : Childhood malnutrition and morbidity remain significant public health challenges in Ethiopia, highlighting the need to assess the risk factors contributing to these issues for effective prevention and control strategies. Thus, this study aims to investigate the underlying risk factors by employing a structural equation model to analyze malnutrition as a mediator in the relationship between selected factors and morbidity. METHODS : The study utilized data from the 2016 Ethiopia Demographic and Health Survey and a sample of 8,560 under-five children were considered. The structural equation model was used to examine the association between child malnutrition, morbidity, and potential risk factors. The structural equation model makes it possible to analyze malnutrition as a mediator of the association between selected risk factors and morbidity. RESULTS : Out of the 8,560 sampled children, 12.80% were wasted, 34.75% were stunted, 23.91% were underweight, 13.9% had fever, 11.2% had diarrhea, and 59.7% had anemia. Birth interval, wealth index household, place of delivery, size of child at birth, number of children, and socioeconomic condition had a significant direct effect on childhood malnutrition and morbidity. The time to get water, toilet facility, and child is a twin variables had direct effects on childhood malnutrition and had no significant direct effects on childhood morbidity. Time to get water, birth interval, toilet facility, wealth index of household, child is a twin, place of delivery, size of child, and number of children exhibited an indirect effect on morbidity through malnutrition. CONCLUSIONS : The study revealed that there was a high prevalence of malnutrition and morbidity among under-five children in Ethiopia. Time to get water in min, place of delivery, size of child, and number of children showed a significant indirect and total effect on morbidity through malnutrition and socioeconomic conditions showed a significant total effect on morbidity via malnutrition. Implementing and extending programs such as community-based nutrition interventions for early childhood is critical, as early malnutrition showed long-term effects on growth and immunity, particularly in the regions of Affar, Dire Dawa, Gambela, Harari, Amhara, and Somali.
Exploring the impact of a maternal support grant to improve mental health and food security amongst pregnant women in South Africa during the COVID-19 pandemic
(Wiley, 2024-09) Laurenzi, Christina A.; Menyatsoe, Masedi; Shuaib, Mustafa; Edwards, Amanda; Gemmell, Kelly; Geffen, Hayli; Tomlinson, Mark; Muller, Anna‐Marie; Manda, S.O.M. (Samuel); Mabaso, Kopano M.
Social protection during pregnancy may support pregnant women struggling to meet basic needs to ensure a healthy pregnancy and buffer negative impacts of multiple adversities. We assessed the effect of a bimonthly digital food voucher, delivered to pregnant women during the COVID-19 pandemic in the Cape Town area, on their mental health, hunger, and dietary diversity. Pregnant women from antenatal clinics in specific high-poverty areas were invited to join the voucher program; a subset was recruited for in-depth telephone interviews. Interviews were conducted before, during, and after voucher distribution. Generalized estimating equations were fit to examine whether each outcome was associated with voucher exposure over time. Of the 205 participants, most were aged 25–34, not recently employed, with at least one child in their household. Approximately 1/3 were first-time mothers and 32% reported mental health difficulties. Voucher exposure over 12 months was associated with significant reductions in mental health symptoms at midline and endline. Maternal hunger was reduced at midline and endline. High mental health scores were significantly associated with increased maternal hunger after adjusting for potential confounders. This study provides preliminary evidence for income support during pregnancy to shape positive health outcomes in South Africa.
Generalized bivariate Kummer-beta distribution with marginals defined on the unit interval
(Public Library of Science, 2024-10-28) Shabgard, Sina; IranmaneshID, Anis; Rad, Najmeh Nakhaei; Nagar, Daya K.; Nadarajah, Saralees
In this paper, a generalized bivariate Kummer-beta distribution is proposed. The name derives from the fact that its particular cases include univariate Kummer-beta distributions. This distribution generalizes a number of existing bivariate beta distributions, including Nadarajah’s bivariate distributions, Libby and Novick’s bivariate beta distribution and a central bivariate Kummer-beta distribution. Various properties associated with this newly introduced distribution are derived. The derived properties include product moments, marginal densities, marginal moments, conditional densities, conditional moments, Rényi entropy and Shannon entropy. Motivated by possible applications in economics, genetics, hydrology, meteorology, nuclear physics, and reliability, we also derive distributions of the product and the ratio of the components following the proposed distribution. Parameter estimation by maximum likelihood method is discussed by deriving expressions for score functions. Inference based on maximum likelihood estimation supposes that the maximum likelihood estimators have zero bias and zero mean squared errors. A simulation study is performed to check this for finite samples.
Additive modeling of zonal level crop production in Ethiopia
(Nature Research, 2025-04) Mare, Yidnekachew; Zewotir, Temesgen; Belay, Denekew Bitew
Crop production is the main source of food security and income for smallholder private farmers in Sub-Saharan countries. To have a sustainable source of food security and economy, it is important to identify covariates that affect crop production linearly and nonlinearly. Annual agricultural sample survey data of eight Meher seasons, from 2012/13 to 2019/20, is used in this study with the main objective of identifying the set of covariates that have linear and nonlinear effects on crop production and estimating their effects using an additive mixed effects model. The minimum, mean, and maximum crop production across the country for the study period were 1.616, 8.693, and 147.843 quintals, respectively, and 50% of the farmers produced less than 6.95 quintals. The histogram, kernel density, and P-P plots suggested that log-transformed crop production is approximately normally distributed. From the competing models’ summary statistics, information criteria values, and analysis of variance tests, relaxing the linearity assumption and including a random effect in the model has improved model performance, suggesting the additive mixed effects model best fits the data on hand. Gambella, SNNP, and Oromia regions have significantly different overall mean crop production than the reference in Dire Dawa town. Covariates like year, proportion of female farmers, household age, and UREA fertilizer used have a significant nonlinear effect, while covariates like proportion of educated farmers, area used, and proportion of farmers who received credit service have a significant linear effect on log crop production. The basic model assumptions are not violated, so the final additive mixed effects model can be used for prediction and inference purposes. We recommend farmers use more croplands, indigenous seeds, and UREA fertilizer; practice pure agriculture; and participate in local farmers associations. Policies regarding the participation of female and educated farmers, the implementation and effectiveness of credit services and extension programs, private investors to participate in crop production, and the provision of farm inputs to the elderly farmers should be revised.
Behaviour of commercial layer hens in enriched cages and floor systems examined using human and video-based observations
(South African Society for Animal Science, 2025-06) Chilemba, Timothy.; Van Marle-Koster, Este; Masenge, Andries; Cromhout, M.; Nkukwana, Thobela T.; evm.koster@up.ac.za
There is considerable pressure to eliminate the use of conventional cages in commercial layer hen production systems. However, the assessment of alternative systems that can ensure the hen's ability to perform natural behaviours, while simultaneously enhancing farm productivity and economic efficiency, remains incomplete. This study assessed layer behaviour in a floor system and in enriched cages on a commercial layer farm using human and video-based observations. The study focused on dust bathing, nesting, feather pecking, and perching behaviours, and on the formation of mud balls on the feet. A large proportion (72.9%) of the hens exhibited dust-bathing behaviour, with an average duration of 22.63 minutes. Feather pecking was exhibited by 35.4% of layers in the enriched cages, compared to 58.3% of layers in the floor system. Overall, feather pecking was the least observed behaviour. Layers in enriched cages used perches more (47%) than layers in the floor system (27%), and a negative association was found between body weight and perching in layers in the floor system. At the end of the six-week trial period, 41.67% of the hens had developed mud balls on their toes that exceeded 3 cm in length. The results of this study provide evidence of the relationships between poultry behaviour, welfare, and production. Video-based observations confirmed that farm managers may not be able to identify certain welfare-related behavioural aspects unless they are closely monitored. The results of this study may be used to inform stakeholders about behaviour and welfare considerations in the management of commercial layers.
Identifying the associated risk factors of time to first antenatal care contacts among pregnant women in Somalia : a survival frailty approach
(Bentham Science Publishers, 2025-01) Belay, Denekew Bitew; Fentaw, Kenaw Derebe; Ali, Mahad Ibrahim; Rad, Najmeh Nakhaei; Chen, Ding-Geng (Din)
BACKGROUND : Antenatal care (ANC) utilization offers a wide range of interventions, such as education, counseling, screening, treatment, monitoring, and supporting the health of pregnant women, making it a significant opportunity for expectant mothers. This study aims to investigate the time to the first ANC contact among pregnant women and to identify associated factors by employing the Accelerated Failure Time (AFT) model using different frailty distributions. METHODS : This study used Somalia's Health and demographic survey data. A sample of 3138 women of reproductive age (15-49 years) were included in the study and accelerated failure time (AFT) models with different frailty distributions were compared using information criteria to select the best model. RESULTS : Among the women included in this study, only 33.1% of them received their first ANC contacts within the recommended time during their pregnancy. A gamma frailty model with log-logistic as base-line distribution was found to be the best model for the time-to-first ANC utilization for our data. The final model, based on the log-logistic gamma frailty, identified marital status, mother's occupation, wanted pregnancy, region, parity, wealth index, education level of mother, persons deciding on mother health care, and media exposure are significant (p-value <0.05) predictors of time to the first ANC contact in Somalia. The final model evidenced a high degree of heterogeneity at an individual level regarding the time to the first ANC utilization in Somalia. CONCLUSION : The median time for the first ANC contact among pregnant women was 6.2 months. To ensure accurate analysis and better policy recommendation, different candidate models were compared, and the univariate gamma frailty model with a log-logistic baseline was found to be the most appropriate approach for analyzing time to the first ANC contact among pregnant women. Maternal and child health policies and initiatives must better focus on women's development and implement interventions aimed at increasing the timely initiation of prenatal care services. More specific policy measures, such as targeted educational campaigns, improved pregnancy services, and efforts to minimize regional disparities, should be prioritized as urgent intervention mechanisms.
Meta-analysis of the prevalence of tuberculosis in cattle and zoonotic tuberculosis in humans in sub-Saharan Africa
(BioMed Central, 2025-04) Ngwira, Alfred; Manda, S.O.M. (Samuel); Karimuribo, Esron Daniel; Kimera, Sharadhuli Iddi
BACKGROUND : Tuberculosis (TB) in cattle negatively affects the cattle economy in Africa, with zoonotic TB posing drug-resistance issues in humans. The burden of TB in cattle and zoonotic TB in humans in sub-Saharan Africa (SSA) is not well understood. This study aimed to determine the prevalence of both TB in cattle and zoonotic TB in humans in SSA through meta-analysis. METHODS : Research on TB prevalence was sourced from multiple databases. A random effects meta-analysis model estimated TB prevalence in SSA and its regions, while meta-regression identified risk factors. The analysis included 114 studies for cattle and 59 for humans. RESULTS : The estimated TB prevalence in cattle was 5.06% (95% CI: 3.76–6.78), with a higher burden in West Africa. The prevalence was greater on farms than at abattoirs. Among humans, M. bovis prevalence was 0.73% (95% CI: 0.53–1.01), increasing to 1.56% (95% CI: 1.04–2.33) in TB incident cases, especially in the West and East Africa. Higher prevalence was noted among livestock workers, and in drug-resistant cases. Significant factors influencing TB prevalence varied for cattle and humans, including country, diagnostic methods, and study populations. CONCLUSION : Focusing interventions on farms and livestock workers could help reduce the disease burden.
Factors that affected South African students’ sense of self-perceived academic competence during the COVID-19 lockdown and the rapid transition to online learning
(MDPI, 2025-02) Law-Van Wyk, Eloise; Visser, Maretha; Masenge, Andries; eloise.law-vanwyk@up.ac.za
The COVID-19 pandemic lockdown restrictions had significant impacts on the well-being and academic functioning of students worldwide. When universities closed campuses and moved teaching and learning online, students faced numerous challenges. The researchers conducted a study to establish which factors most affected South African students’ academic competence during the initial months of lockdown and the shift to online learning. Using an online survey that focused on students’ wellness, perceived academic competence and coping behaviour, data were collected from 3239 university students. Multiple linear regression showed that students’ subjective sense of intellectual wellness, coping behaviour, satisfaction with support from the university, and mental health were strong predictors of academic competence. Other factors that influenced students’ academic competence were emotional and spiritual wellness, perceptions of safety and security, and hopefulness. Females, undergraduates, and Faculty of Law students reported higher perceptions of academic competence. These findings have practical implications for universities as they identify factors that contribute to students’ academic competence, especially during times of crisis and online learning. Academic and support services staff at universities may find the findings valuable when developing policies to provide appropriate resources and services to promote and sustain students’ academic functioning.
Prevalence and associated factors of immunization among under-five children in Somalia
(BioMed Central, 2025-03) Belay, Denekew Bitew; Ali, Mahad Ibrahim; Chen, Ding-Geng (Din); Jama, Umalkhair Abdi
BACKGROUND : Children worldwide can live lives free from various illnesses and disabilities due to vaccination. For instance, vaccination has eliminated smallpox, a deformative and frequently fatal illness that claimed an estimated 300 million lives in the twentieth century. However, due to a lack of access to immunization and other health services, 14.3 million infants in 2022 still did not receive their first dose of the Diphtheria-Tetanus-Pertussis (DTP) vaccine, and an additional 6.2 million received only a portion of the scheduled dose. This study aimed to assess prevalence and determinant factors of immunization among under-five children in Somalia using Somalia Health and Demographic Survey (SHDS) Data. METHODS : The study design was cross-sectional, utilizing the SHDS 2020 data. A total of 3916 under-five children who fulfilled the inclusion criteria were included in this study. Count regression models were employed to explore factors associated with the number of vaccinations received per child. RESULTS : In this study, 9.14% of children did not receive any vaccination during their childhood. Different candidate count regression models were compared. Using AIC and BIC, the Negative-binomial (NB) regression model was found to be the best fit. From this model, we found that women ages 20–24 (IRR = 1.192, 95% CI: 1.083, 1.313) and 25–29 (IRR = 1.180, 95% CI: 1.068, 1.305) had a higher number of vaccinations per child compared to women in the 15–19 age group. Women who attended primary education (IRR = 1.090, 95% CI: 1.034, 1.150) and secondary education (IRR = 1.157, 95% CI: 1.058, 1.266) had a higher number of vaccinations per child compared to uneducated women) also correlated with increased vaccination Parity (IRR = 1.090, 95% CI: 1.031–1.153), and wealth quantile (IRR = 1.110, 95% CI: 1.012, 1.217) positively influenced vaccination attendance. Regional disparities were also found to be significant, with Togdheer, Sool, Sanaag, Bari, Nugaal, Bay, Bakool, Mudug, Hiiraan and Galgaduud significantly different from Awdal region. In Negative-Binomial, age, region, residence, educational level, wealth quantile, child size at birth, parity and birth order emerged as key predictors, revealing complex determinants of vaccination utilization in Somalia. CONCLUSIONS : A large proportion of children did not complete the full vaccination schedule. Socio-demographic factors, such as age, region, residence, educational level, wealth quantile, child size at birth, parity, and birth order, had a significant impact on the number of children vaccinated in Somalia. These findings underscore the importance of targeted interventions for addressing these factors. Implementing initiatives based on these conclusions has the potential to enhance vaccination coverage and child health outcomes.
Improved runs-rules precedence charts for monitoring the process location parameter
(Springer, 2025-04) Human, Schalk William; Malela-Majika, Jean-Claude; Kritzinger, Pierre; malela.mjc@up.ac.za
Runs-rules are typically incorporated into control charts to increase their sensitivity to detect small process shifts. However, a drawback of this approach is that the resulting charts are unable to detect large shifts quickly. In this paper, improved runs-rules are introduced to the nonparametric precedence chart to address this limitation by maintaining the sensitivity to small process shifts, while improving the ability to detect large shifts in the process. Performance comparisons between the proposed precedence charts and the precedence charts with standard runs-rules are made in terms of their respective run-length characteristics. The results reveal that the precedence charts with improved runs-rules are superior to the competing charts in detecting large shifts in the process, while maintaining the same sensitivity in the detection of small shifts. A real-life example from the engineering field is given to demonstrate the application and implementation of the new charts.
A power-cardioid candidate for wind direction modelling motivated by two South African case studies
(Springer, 2025-04) Van Wyk-de Ridder, Delene; Rad, Najmeh Nakhaei; Arashi, Mohammad; Ferreira, Johan; Bekker, Andriette, 1958-; johan.ferreira@up.ac.za
Wind energy claims a positive image globally; therefore, accurate modelling of wind direction at generation sites accurately can enhance the potential of this green energy source. The uncertain nature of wind direction can be modelled through probability distributions; in this paper, we propose a flexible yet simple distribution, namely the Power-Cardioid distribution, as an alternative and implementable candidate to model wind direction. After discussing some characteristics, the performance of the Power-Cardioid distribution is evaluated via a simulation study and applied to datasets of two wind farms in South Africa. The numerical results demonstrate that this distribution is a promising and exciting new candidate compared to well-known models within circular statistics.
Development and validation of a knowledge, attitudes and practices (KAP) questionnaire for healthcare professionals on environmental sustainability in healthcare in Southern Africa
(F1000 Research Ltd, 2024-10) Lister, Helga Elke; Mostert, Karien; Botha, Tanita; Field, Emma; Knock, Danté; Mubi, Natasha; Odendaal, Stefani; Rohde, Megan; Maric, Filip
BACKGROUND: The triple planetary crisis of climate change, environmental pollution, and biodiversity loss is increasingly driving poor health outcomes worldwide. Healthcare systems and services are often not environmentally sustainable and compound the problem, while healthcare professionals are also recognised as key leaders in advancing sustainable healthcare. To adopt this leadership position, healthcare professionals’ knowledge, attitudes, and practices regarding environmental sustainability in healthcare must be established. This article reports the development and validation of a new instrument for this purpose that corresponds to the specificities of the Southern African context. METHODS: Questionnaire development followed a seven-stage process. Information was obtained from a 2021 study titled ‘South African Healthcare Professionals’ Knowledge, Attitudes, and Practices Regarding Environmental Sustainability in Healthcare: A Mixed Methods Study’ to develop the instrument. Information was also sourced from the literature regarding environmental sustainability and healthcare to generate the first questionnaire with 29 items. The following stages included two rounds of expert input, separated by a pilot study with the target population to receive feedback regarding the instrument’s structure, relevance, and length. Content validity was determined through statistical analysis. RESULTS: Feedback was received from nine experts in stage two and 13 pilot study participants in stage four and incorporated to improve the questionnaire. In stage six, the questionnaire was rated by seven experts. The content validity index of the questionnaire was calculated at two different stages, after which the indices were compared. Following a final edit, the questionnaire has 24 questionnaire items. The closing analysis calculated the scale content validity index average (S-CVI/Ave) of 0,922; this indicates that the final questionnaire has excellent content validity. CONCLUSION: A questionnaire that assesses the knowledge, attitudes and practices of healthcare professionals regarding environmental sustainability in Southern Africa has been developed and validated. This questionnaire can now be used for further studies in Southern Africa.
Robust PCA with Lw,∗ and L2,1 norms : a novel method for low-quality retinal image enhancement
(MDPI, 2024-07) Likassa, Habte Tadesse; Chen, Ding-Geng (Din); Chen, Kewei; Wang, Yalin; Zhu, Wenhui
Please read abstract in the article.
An optimised rabies vaccination schedule for rural settlements
(Elsevier, 2025-03) Botes, Rian Hendrik; Fabris-Rotelli, Inger Nicolette; Mahloromela, Kabelo; Chen, Ding-Geng (Din); inger.fabris-rotelli@up.ac.za
Please read abstract in the article.
Mortality trends and causes of death in a South African hospital complex pre- and during COVID-19
(AOSIS, 2025-03) Tshabalala, Khanyisile; Fabris-Rotelli, Inger Nicolette; Basu, Debashis; Myburgh, Magriet; Abdullah, Fareed; khanyisile.tshabalala@ up.ac.za
BACKGROUND : Before coronavirus disease 2019 (COVID-19), global health was improving, with declining mortality trends. The pandemic disrupted this progress, increasing mortality in South Africa between April 2020 and March 2022. Pre-pandemic data establishes a baseline for assessing COVID-19’s impact on all-cause mortality. OBJECTIVES : This study examines changes in hospital-based mortality trends in a Gauteng hospital complex from April 2018 to March 2022, addressing the scarcity of such studies during the COVID-19 era. METHOD : A retrospective review of 7815 deaths from April 2018 to March 2022 was conducted. Chi-squared tests were used to analyse deaths by age group and gender, with correlations reported. RESULTS : Mortality rates rose from 3.2% in 2018–2019, peaked at 5.1% in 2020–2021, and declined to 4.2% in 2021–2022. Patients aged 15 years–64 years had the highest death rates, with an increase among those over 65. Male deaths exceeded female deaths, with the smallest difference observed in 2020–2021. Leading causes of death included diseases of the circulatory and respiratory systems, neoplasms, digestive system diseases, and infectious and parasitic diseases. CONCLUSION : The study highlights COVID-19’s impact on mortality, showing variations by year, age, gender, and disease. Contribution: Excess non-COVID-19 deaths likely stemmed from disrupted healthcare services. These findings underscore the need for ongoing monitoring of hospital mortality to identify pandemic-related service disruptions and guide interventions to strengthen healthcare services, improve access to care, and enhance referral systems during unexpected disasters.
Contest competition and injury in adult male sub-Antarctic fur seals
(Springer, 2024-05) Bester, Marthan Nieuwoudt; Rossouw, G.J.; Van Staden, Paul Jacobus; mnbester@zoology.up.ac.za
We recorded intra-sexual behaviour of adult male sub-Antarctic fur seals Arctocephalus tropicalis at Gough Island, Southern Ocean, during the 1975/76 summer breeding season. Our re-analysed data address male ‘contest competition’, which relates to the costs of intra-sexual disputes, including fights. We considered the risks/benefits of fighting through investigation of injuries (n = 353) sustained by adult males (n = 124) in fights. Injuries were predominantly on the forequarters, especially around the insertion areas of the front flippers (41%) with its sparse pelage, compared to the neck and chest areas combined (29%), an area which is well protected by thick pelage. The infliction of serious, sometimes debilitating, injuries to competitors increases a male’s access to females. Injuries predominate in injured, defeated males that gather at non-breeding sites, suggesting that injuries inflicted by dominant males were successful in excluding competing males from breeding sites.
Partial proportional odds of child polio vaccination status among children aged 12–23 Months in Ethiopia
(Wiley, 2025-04) Belay, Alebachew Taye; Belay, Denekew Bitew; Yilema, Seyifemickael Amare; Moyehodie, Yikeber Abebaw
BACKGROUND : The poliovirus is mostly transmitted by the fecal–oral route and can cause viremia after replication in the gastrointestinal tract. The current global coverage of polio immunization is 85%, against the 90% target, while the total coverage of inactivated polio vaccine (IPV) coverage in sub-Saharan Africa is 73%. Only 30% of the children living in rural areas of Ethiopia were fully vaccinated at the appropriate ages in 2016 EDHS (Ethiopian Demographic and Health Survey) data. This study evaluated the prevalence and factors associated with the vaccination status of children aged 12 and 23 months in Ethiopia. METHODS : The Ethiopian Mini Demographic and Health Survey 2019 (Mini EDHS, 2019) was used for this study. The partial proportional ordinal logistic regression model was used to determine the risk factors associated with the polio vaccination status of children aged 12 and 23 months using SAS version 9.40 statistical software at a 5% level of significance. RESULTS : The prevalence of polio vaccination status of children showed that about 33.00% of children never received vaccination, 21.20% were partially vaccinated, and 45.70% were fully vaccinated. The age of mother (AOR [adjusted odds ratio] = 1.06, 95% CI: 1.025, 1.094), age of mother at the first birth (AOR = 0.94, 95% CI: 0.909, 0.976), rural residence (AOR = 0.66; 95% CI: 0.499, 0.867), higher education (AOR = 1.25; 95% CI: 1.241, 1.730), at least four and more ANC (AOR = 2.34; 95% CI: 1.845, 2.968), and ANC visits in health facilities (AOR = 2.33, 95% CI: 1.902, 2.864) had a significant effect on child polio vaccination. CONCLUSION : The coverage of full polio vaccination in Ethiopia was below 50%, which is below the global and regional percentage. Policies and programs must be formulated and implemented with a strong focus on women who have not used ANC visits, residents in rural areas, and uneducated women in child vaccination must be considered in Ethiopia.
The impact of past and current district-level climatic shifts on maize production and the implications for South African farmers
(Springer, 2025-02) Mangani, Robert; Mazarura, Jocelyn; Matlou, Solly; Marquart, Arnim; Archer, Emma Rosa Mary; Creux, Nicky; nicole.creux@fabi.up.ac.za
South Africa’s climate studies generally focus on coarser provincial levels, which aid policy recommendations, but have limited application at the farm level. District level climate studies are essential for farmer participation in climate change mitigation strategies and management. Our study aimed to investigate historical climate data for trends and their influence on maize yields at the magisterial level. Six sites were selected from three major maize-producing provinces in South Africa: Mpumalanga, Northwest, and Free State. Magisterial districts in each province were selected from different Köppen-Geiger climate zones. The climate variables assessed by the Mann–Kendall trend test included maximum or minimum temperature, rainfall, number of extreme high-temperature days, rainfall onset and cessation from 1986 to 2016. The average maximum temperatures were observed to have significant upward trends in most locations, except for Schweizer-Reneke and Bethlehem. The fastest rate of change was observed at Klerksdorp (0.1 °C per 30 years of study), while the Schweizer-Reneke district was the slowest (0.05 °C per 30 years of study). No significant changes were observed in rainfall onset, cessation, or total rainfall in Schweizer-Reneke, Standerton, and Bethlehem, which are scattered across the different provinces. The other districts in each province showed significant changes in these parameters. Rainfall accounted for the significant variation in maize yields over the study period, explaining between 18 and 40% of the variation in the North West, and between 1 and 17% in the Free State. These findings highlight the importance of understanding location-specific changes at a finer scale, which can help farming communities adjust agronomic practices and adapt to local climate shifts.

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