Publications by authors named "Onyango Clayton"

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  • The study investigates the role of meningitis in child mortality under five years old, particularly focusing on data from six sub-Saharan African countries and Bangladesh.
  • It employs post-mortem minimally invasive tissue sampling (MITS) to identify the causes of death and pathogens responsible for meningitis in this age group from December 2016 to December 2023.
  • Findings reveal that meningitis contributed to 7% of child deaths, with common pathogens identified being Acinetobacter baumannii and Klebsiella pneumoniae, particularly affecting neonates and infants.
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  • Researchers conducted surveillance for avian influenza viruses in domestic and wild birds near Lake Victoria, Kenya, due to nearby outbreaks in other countries.
  • They tested over 14,000 specimens and found that 3.9% of poultry samples and 0.2% of wild bird fecal samples were positive for the virus, with most poultry infections being H9N2.
  • Despite not detecting highly pathogenic H5N8, the study emphasizes the risk of HPAI virus introduction and establishment in the region, particularly through live bird markets.
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The epidemiology and circulation patterns of various rhinovirus types within populations remains under-explored. We generated 803 VP4/VP2 gene sequences from rhinovirus-positive samples collected from acute respiratory illness (ARI) patients, including both in-patient and outpatient cases, between 1st January and 31st December 2014 from eleven surveillance sites across Kenya and used phylogenetics to characterise virus introductions and spread. RVs were detected throughout the year, with the highest detection rates observed from January to March and June to July.

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Background: Respiratory syncytial virus (RSV) is one of the main causes of hospitalization for lower respiratory tract infection in children under five years of age globally. Maternal vaccines and monoclonal antibodies for RSV prevention among infants are approved for use in high income countries. However, data are limited on the economic burden of RSV disease from low- and middle-income countries (LMIC) to inform decision making on prioritization and introduction of such interventions.

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  • Kenya introduced the 10-valent pneumococcal conjugate vaccine, Synflorix™, in 2011, and early surveys indicated a decline in vaccine-type pneumococcal colonization among children but there was limited information on its long-term effectiveness.
  • A 2017 cross-sectional survey in Kibera and Asembo involved 504 children under 5, showing a significant reduction in overall pneumococcal colonization compared to 2013, with over 90% of participants having received three doses of the vaccine.
  • Despite the decrease in overall colonization, the prevalence of PCV10-GSK serotypes remained relatively stable, indicating a plateau effect in vaccine-type carriage six years after the vaccine's
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To describe RDS in neonatal deaths at the CHAMPS-Kenya site between 2017 and 2021. We included 165 neonatal deaths whose their Causes of death (COD) were determined by a panel of experts using data from post-mortem conducted through minimally invasive tissue specimen testing, clinical records, and verbal autopsy. Twenty-six percent (43/165) of neonatal deaths were attributable to RDS.

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  • The study investigates SARS-CoV-2 exposure in two distinct populations in Kenya—one urban (Kibera) and one rural (Asembo)—by measuring seroprevalence at two different times in 2021.
  • Results showed an increase in seroprevalence from March to June/July 2021, with urban Kibera reaching 63.9% and rural Asembo 48.7%, highlighting significant geographical disparities.
  • The low vaccination rates at the time (only 1.2% and 1.6%) indicate a need for strengthened public health measures to combat further spread of the virus.
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  • A study in rural Kenya found that 41% of asymptomatic residents had antibodies against the SARS-CoV-2 spike protein, and 82.5% exhibited T cell responses to multiple viral proteins, indicating some level of immunity despite not showing symptoms.
  • The immune response profile in Kenyan participants was distinct from those in Europe and Asia, exhibiting strong reactions to accessory proteins rather than structural ones and a unique cytokine balance (higher IL-10 to IFN-γ ratio).
  • These findings suggest that current methods of measuring COVID-19 prevalence may underestimate infections in asymptomatic populations, and highlight the potential influence of environmental factors on immune responses in Africa.
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Background: To address knowledge gaps regarding diarrheagenic Escherichia coli (DEC) in Africa, we assessed the clinical and epidemiological features of enteroaggregative E. coli (EAEC), enteropathogenic E. coli (EPEC), and Shiga toxin-producing E.

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Background: Non-typhoidal Salmonella (NTS) is a common cause of gastroenteritis in young children, with limited data on NTS serovars and antimicrobial resistance in Africa.

Methods: We determined the prevalence of Salmonella spp. and frequency of antimicrobial resistance among serovars identified in stools of 0-59 month-old children with moderate-to-severe diarrhea (MSD) and controls enrolled in the Vaccine Impact on Diarrhea in Africa (VIDA) Study in The Gambia, Mali, and Kenya in 2015-2018, and compared with data from the Global Enteric Multicenter Study (GEMS; 2007-2010) and the GEMS-1A study (2011).

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We investigated the first 152 laboratory-confirmed SARS-CoV-2 cases (125 primary and 27 secondary) and their 248 close contacts in Kisumu County, Kenya. Conducted June 10-October 8, 2020, this study included interviews and sample collection at enrolment and 14-21 days later. Median age was 35 years (IQR 28-44); 69.

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Objective: Identifying factors that may influence aflatoxin exposure in children under 5 years of age living in farming households in western Kenya.

Design: We used a mixed methods design. The quantitative component entailed serial cross-sectional interviews in 250 farming households to examine crop processing and conservation practices, household food storage and consumption and local understandings of aflatoxins.

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  • * A study in Kenya evaluated the performance of the Panbio™ Ag RDT against rRT-PCR in 2,245 individuals, revealing overall sensitivity of 46.6% and specificity of 98.5%, with better sensitivity in symptomatic individuals compared to asymptomatic ones.
  • * The findings showed that although the specificity of the Ag RDT was satisfactory, its sensitivity was significantly lower than anticipated, suggesting limited effectiveness in detecting infections, especially after several days of symptoms.
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  • Rhinoviruses (RV) present in humans show a lot of genetic variation, but their behavior in different social environments is not well studied.
  • This research investigated RV dynamics in Kenya by examining genetic sequences from various settings, including households, a school, and health facilities, finding the highest diversity of RV types at the nationwide level.
  • The study underscores the importance of social structures in influencing RV dynamics and suggests that understanding these patterns can improve public health strategies, with future research focusing on whole-genome analysis for deeper insights.
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We estimated the prevalence of extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE), carbapenem-resistant Enterobacterales (CRE), and methicillin-resistant Staphylococcus aureus (MRSA) in communities and hospitals in Kenya to identify human colonization with multidrug-resistant bacteria. Nasal and fecal specimen were collected from inpatients and community residents in Nairobi (urban) and Siaya (rural) counties. Swabs were plated on chromogenic agar to presumptively identify ESCrE, CRE and MRSA isolates.

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  • Existing acute febrile illness (AFI) surveillance systems can be adapted to identify new diseases like COVID-19 by testing patients who show symptoms.
  • The CDC worked with health ministries in five countries (Belize, Ethiopia, Kenya, Liberia, and Peru) to integrate COVID-19 testing into their AFI systems from March 2020 to October 2021, enrolling over 5,500 patients.
  • Testing results showed varying positivity rates for SARS-CoV-2 across countries, demonstrating that AFI surveillance can effectively enhance monitoring and response to emerging infectious diseases.
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  • Kenya's Ministry of Health and the US CDC Kenya have collaborated for 40 years to address various disease threats, including during the COVID-19 pandemic.
  • Together, they implemented joint activities to reduce COVID-19's impact on Kenya's population, including establishing emergency operations centers and enhancing surveillance and training programs.
  • The pandemic prompted the Kenyan government to launch a national public health institute in January 2022 to strengthen public health efforts against current and future health threats.
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Background: We used postmortem minimally invasive tissue sampling (MITS) to assess the effect of time since death on molecular detection of pathogens among respiratory illness-associated deaths.

Methods: Samples were collected from 20 deceased children (aged 1-59 months) hospitalized with respiratory illness from May 2018 through February 2019. Serial lung and/or liver and blood samples were collected using MITS starting soon after death and every 6 hours thereafter for up to 72 hours.

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Background: Minimally invasive tissue sampling (MITS) is an alternative to complete autopsy for determining causes of death. Multiplex molecular testing performed on MITS specimens poses challenges of interpretation, due to high sensitivity and indiscriminate detection of pathogenic, commensal, or contaminating microorganisms.

Methods: MITS was performed on 20 deceased children with respiratory illness, at 10 timepoints up to 88 hours postmortem.

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Background: Lower respiratory tract infections are a leading cause of death in young children, but few studies have collected the specimens needed to define the role of specific causes. The Child Health and Mortality Prevention Surveillance (CHAMPS) platform aims to investigate causes of death in children aged <5 years in high-mortality rate settings, using postmortem minimally invasive tissue sampling and other advanced diagnostic techniques. We examined findings for deaths identified in CHAMPS sites in 7 countries in sub-Saharan Africa and south Asia to evaluate the role of respiratory syncytial virus (RSV).

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We determined incidence of severe acute respiratory syndrome coronavirus 2 and influenza virus infections among pregnant and postpartum women and their infants in Kenya during 2020-2021. Incidence of severe acute respiratory syndrome coronavirus 2 was highest among pregnant women, followed by postpartum women and infants. No influenza virus infections were identified.

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Background: In resource-limited settings, acute respiratory infections continue to be the leading cause of death in young children. We conducted postmortem investigations in children <5 years hospitalized with a clinical diagnosis of respiratory disease at Kenya's largest referral hospital.

Methods: We collected respiratory and other tissues postmortem to examine pathologic processes using histology, molecular and immunohistochemistry assays.

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Background: Brucellosis occurs globally with highly variable incidence in humans from very low in North America and Western Europe to high in the Middle East and Asia. There are few data in Sub-Saharan Africa. This study estimated the incidence of human brucellosis in a pastoralist community in Kenya.

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Understanding respiratory syncytial virus (RSV) circulation patterns is necessary to guide the timing of limited-duration interventions such as vaccines. We describe RSV circulation over multiple seasons in three distinct counties of Kenya during 2006-2018. Kilifi and Siaya counties each had consistent but distinct RSV seasonality, lasting on average 18-22 weeks.

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Article Synopsis
  • This study focused on the causes of severe acute respiratory infections (SARI) in adults across six countries, using advanced testing methods to identify multiple pathogens.
  • Researchers enrolled 2,388 SARI patients and 1,135 asymptomatic adults, finding that 76% of SARI patients had at least one detectable pathogen, commonly Haemophilus influenzae and Streptococcus pneumoniae.
  • The analysis suggested that specific pathogens, including various strains of influenza and RSV, significantly contributed to SARI cases, highlighting the potential benefits of flu vaccination and the need for RSV vaccine development to lessen SARI prevalence.
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