Browsing by Author "Bulimo, Wallace"

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    Assessing antigenic drift and phylogeny of influenza A (H1N1) pdm09 virus in Kenya using HA1 sub-unit of the hemagglutinin gene
    (Public Library of Science, 2020) Opanda, Silvanos; Bulimo, Wallace; Gachara, George; Ekuttan, Christopher; Amukoye, Evans
    Influenza A (H1N1) pdm09 virus emerged in North America in 2009 and has been established as a seasonal strain in humans. After an antigenic stasis of about six years, new antigenically distinct variants of the virus emerged globally in 2016 necessitating a change in the vaccine formulation for the first time in 2017. Herein, we analyzed thirty-eight HA sequences of influenza A (H1N1) pdm09 strains isolated in Kenya during 2015–2018 seasons, to evaluate their antigenic and molecular properties based on the HA1 sub-unit. Our analyses revealed that the A (H1N1) pdm09 strains that circulated in Kenya during this period belonged to genetic clade 6B, subclade 6B.1 and 6B.2. The Kenyan 2015 and 2016 isolates differed from the vaccine strain A/California/07/2009 at nine and fourteen antigenic sites in the HA1 respectively. Further, those isolated in 2017 and 2018 correspondingly varied from A/Michigan/45/2015 vaccine strain at three and fifteen antigenic sites. The predicted vaccine efficacy of A/California/07/2009 against Kenyan 2015/2016 was estimated to be 32.4% while A/Michigan/45/2015 showed estimated vaccine efficacies of 39.6% - 41.8% and 32.4% - 42.1% against Kenyan 2017 and 2018 strains, respectively. Hemagglutinationinhibition (HAI) assay using ferret post-infection reference antiserum showed that the titers for the Kenyan 2015/2016 isolates were 2–8-fold lower compared to the vaccine strain. Overall, our results suggest the A (H1N1) pdm09 viruses that circulated in Kenya during 2015/2016 influenza seasons were antigenic variants of the recommended vaccine strains, denoting sub-optimal vaccine efficacy. Additionally, data generated point to a swiftly evolving influenza A (H1N1) pdm09 virus in recent post pandemic era, underscoring the need for sustained surveillance coupled with molecular and antigenic analyses, to inform appropriate and timely influenza vaccine update.
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    Prevalence and Genotypic Diversity of High-Risk Human Papillomavirus among Women of Reproductive Age in Kilifi County, Kenya
    (Cureus, 2025-04) Kariuki, Hellen W.; Nyamari, Celestine K.; Waweru, Peter M.; Makazi, Patrick M.; Mureithi, Marianne W.; Bulimo, Wallace; Wanjala, Erick; McKinnon, Lyle; Kariuki, Humphrey N.; Onyambu, Frank G.
    Background Human papillomavirus (HPV) is the most common sexually transmitted infection and the primary cause of cervical cancer, a leading cause of cancer-related deaths among women in Kenya. Although many HPV infections resolve on their own, some high-risk types may persist and gradually develop into cervical cancer over several years, providing opportunities for early detection and intervention. However, in low-resource settings like Kilifi County, HPV testing is limited, and alternative screening methods like visual inspection with acetic acid (VIA) are commonly used despite their limitations. Objective This study aimed to assess the prevalence and genotype distribution of high-risk HPV (HR-HPV) among women of reproductive age in Kilifi County, Kenya, to inform targeted public health interventions. Methodology This study was nested within a more extensive cross-sectional study on female genital schistosomiasis and human immunodeficiency virus (HIV). We focus on a stratified sample of 320 women aged 15-50 from Rabai and Magarini sub-counties, Kilifi, Kenya, identified as Schistosoma haematobium hotspots. Participants provided informed consent, and pregnant women were excluded. Clinical data was collected and sociodemographic data collected via questionnaires, while high vaginal and cervical swabs were selfcollected for HPV testing, screening for 24 HR-HPV genotypes. Results Data from 261 women were analyzed. The overall HR-HPV prevalence was 48.7%, with the Magarini subcounty showing a higher prevalence (31.4%) compared to Rabai (17.2%). The most prevalent HPV genotypes were HPV 18 (25.3%), HPV 45 (22.6%), and HPV 16 (12.6%). Co-infections were common, particularly with HPV 18 and 45. HPV 16 was more prevalent in the Rabai subcounty, while HPV 18 and 45 were more common in the Magarini subcounty. Significant associations were found between sexual partnership type, leukocyte levels, and HPV positivity. Conclusion Kilifi County exhibits a high prevalence of HR-HPV, with genotype variations across sub-counties, suggesting differences in risk factors and access to preventive measures. Self-sampling and communitybased screening effectively increased participation and diversity in the study population, highlighting the need for targeted, age-specific screening programs and comprehensive HPV genotyping to enhance cervical cancer prevention strategies in the region.
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    Serotype and Genetic Diversity of Human Rhinovirus Strains that Circulated in Kenya in 2008
    (Wiley Open Access, 2016) Milanoi, Sylvia; Ongus, Juliette R.; Gachara, George; Coldren, Rodney; Bulimo, Wallace
    Background: Human Rhinoviruses (HRVs) are a well-established cause of the common cold and recent studies indicated that they may be associated with severe acute respiratory illnesses (SARIs) like pneumonia, asthma and bronchiolitis. Despite global studies on the genetic diversity of the virus, the serotype diversity of these viruses across diverse geographical regions in Kenya has not been characterized. Objectives: This study sought to characterize the serotype diversity of HRV strains that circulated in Kenya in 2008. Methods: A total of 517 archived nasopharyngeal samples collected in a previous respiratory virus surveillance program across Kenya in 2008 were selected. Participants enrolled were outpatients who presented with influenza-like (ILI) symptoms. Real time RT-PCR was employed for preliminary HRV detection. HRV positive samples were amplified using RT-PCR and thereafter the nucleotide sequences of the amplicons were determined followed by phylogenetic analysis. Results: Twenty five percent of the samples tested positive for HRV. Phylogenetic analysis revealed that the Kenyan HRVs clustered into three main species comprising HRV A (54%), HRV-B (12%) and HRV C (35%). Overall, 20 different serotypes were identified. Intra-strain sequence homology among the Kenyan strains ranged from 58% to 100% at the nucleotide level and 55% to 100% at the amino acid level. Accepted Article This article is protected by copyright. All rights reserved. Conclusion: These results show that a wide range of HRV serotypes with different levels of nucleotide variation were present in Kenya. Furthermore, our data show that HRVs contributed substantially to influenza-like illness in Kenya in 2008.