Publications by authors named "Sammy Wambua"

Rift Valley fever virus (RVFV) is an adaptable arbovirus that can be transmitted by a wide variety of arthropods. Widespread urban transmission of RVFV has not yet occurred, but peri-urban outbreaks of RVFV have recently been documented in East Africa. We previously reported low-level exposure in urban communities and highlighted the risk of introduction via live animal influx.

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Background: The white teatfish, Holothuria fuscogilva, is widely distributed in coastal areas, including waters around coral reefs and seagrasses in the Indo-Pacific. In Kenya, the species is distributed in shallow reefs with higher landings reported from the Vanga-Shimoni-Gazi seascape on the Kenyan south coast. Despite its high exploitation for export and its vulnerable and endangered statuses under IUCN and CITES respectively, Kenya's H.

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Coral reefs face an increased number of environmental threats from anthropomorphic climate change and pollution from agriculture, industries and sewage. Because environmental changes lead to their compositional and functional shifts, coral reef microbial communities can serve as indicators of ecosystem impacts through development of rapid and inexpensive molecular monitoring tools. Little is known about coral reef microbial communities of the Western Indian Ocean (WIO).

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Background: Although nonoptimal vaginal bacteria and inflammation have been associated with increased HIV risk, the upstream drivers of these phenotypes are poorly defined in young African women.

Setting: Mombasa, Kenya.

Methods: We characterized vaginal microbiome and cytokine profiles of sexually active young women aged 14-24 years (n = 168) in 3 study groups: those engaging in formal sex work, in transactional sex, and nonsex workers.

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Background: Persistent infection with high-risk types of human papillomavirus (HPV) is the preeminent factor driving the development of cervical cancer. There are large gaps in knowledge about both the role of pregnancy in the natural history of HPV infection and the impact of HPV on pregnancy outcomes.

Methods: This single-site prospective cohort substudy, nested within an international multisite randomized controlled trial, assessed prevalence, incident cases, and persistence of type-specific HPV infection, and the association between persistence of high-risk HPV infection with pregnancy outcomes among HIV-infected pregnant women in Kenya, including HIV transmission to infants.

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Adolescents and young people are arguably the most dynamic and challenging group among populations living with HIV. The adherence to anti-retroviral treatment (ART) is often low among HIV-positive youth, thus creative and context specific interventions are necessary. We aimed at evaluating the usability and effectiveness of the pilot digital peer support platform - ELIMIKA, implemented in Mombasa, Kenya.

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Introduction: One of the major characteristics of HIV-1 is its extreme genetic diversity. A key factor in assessing the sensitivity of a molecular-based assay measuring HIV-1 RNA viral load (VL) in plasma is its ability to detect/quantify all (or most of) relevant HIV-1 genetic subtype/recombinant forms accurately.

Areas Covered: This review provides an overview of the current commercially available quantitative real-time assays (the Abbott RealTime HIV-1, Roche TaqMan HIV-1 versions 1.

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Both the sickle cell trait (HbAS) and alpha(+)-thalassaemia are common in many tropical areas. While their individual haematological effects are well described, few studies describe their effects when inherited together. We present data from the Kenyan coast, which suggest that HbAS and alpha(+)-thalassaemia may interact to produce specific effects on haematological parameters.

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Background: The alpha-thalassaemias are the commonest genetic disorders of humans. It is generally believed that this high frequency reflects selection through a survival advantage against death from malaria; nevertheless, the epidemiological description of the relationships between alpha-thalassaemia, malaria, and other common causes of child mortality remains incomplete.

Methods And Findings: We studied the alpha+-thalassaemia-specific incidence of malaria and other common childhood diseases in two cohorts of children living on the coast of Kenya.

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The hemoglobinopathies, disorders of hemoglobin structure and production, protect against death from malaria. In sub-Saharan Africa, two such conditions occur at particularly high frequencies: presence of the structural variant hemoglobin S and alpha(+)-thalassemia, a condition characterized by reduced production of the normal alpha-globin component of hemoglobin. Individually, each is protective against severe Plasmodium falciparum malaria, but little is known about their malaria-protective effects when inherited in combination.

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Background: The gene for sickle hemoglobin (HbS) is a prime example of natural selection. It is generally believed that its current prevalence in many tropical populations reflects selection for the carrier form (sickle cell trait [HbAS]) through a survival advantage against death from malaria. Nevertheless, >50 years after this hypothesis was first proposed, the epidemiological description of the relationships between HbAS, malaria, and other common causes of child mortality remains incomplete.

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Background: Malaria resistance by the sickle cell trait (genotype HbAS) has served as the prime example of genetic selection for over half a century. Nevertheless, the mechanism of this resistance remains the subject of considerable debate. While it probably involves innate factors such as the reduced ability of Plasmodium falciparum parasites to grow and multiply in HbAS erythrocytes, recent observations suggest that it might also involve the accelerated acquisition of malaria-specific immunity.

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Although hemoglobinopathies such as alpha+ thalassemia and the sickle cell trait might contribute to anemia in African children, we hypothesized that they might also enhance iron absorption under circumstances of critical availability, and that this could attenuate their hematologic effects. We found no support for this hypothesis in a cohort of children living on the coast of Kenya.

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Although the alpha+ thalassemias almost certainly confer protection against death from malaria, this has not been formally documented. We have conducted a study involving 655 case patients with rigorously defined severe malaria and 648 controls, frequency matched on area of residence and ethnic group. The prevalence of both heterozygous and homozygous alpha+ thalassemia was reduced in both case patients with severe malaria (adjusted odds ratios [ORs], 0.

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