Browsing by Subject "transmission"

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  • Skarp, C. P. A.; Hanninen, M-L; Rautelin, Hilpi I (2016)
    The incidence of human infections caused by Campylobacter jejuni and Campylobacter coil, the main bacterial agents of gastrointestinal disease, has been increasing worldwide. Here, we review the role of poultry as a source and reservoir for Campylobacter. Contamination and subsequent colonization of broiler flocks at the farm level often lead to transmission of Campylobacter along the poultry production chain and contamination of poultry meat at retail. Yet Cainpylobacter prevalence in poultry, as well as the contamination level of poultry products, vary greatly between different countries so there are differences in the intervention strategies that need to be applied. Temporal patterns in poultry do not always coincide with those found in human infections. Studies in rural and urban areas have revealed differences in Campylobacter infections attributed to poultry, as poultry seems to be the predominant reservoir in urban, but not necessarily in rural, settings. Furthermore, foreign travel is considered a major risk factor in acquiring the disease, especially for individuals living in the northern European countries. Intervention strategies aimed at reducing Campylobacter colonization in poultry and focused at the farm level have been successful in reducing the number of Campylobacter cases in several countries. Increasing farm biosecurity and education of consumers are likely to limit the risk of infection. Overall, poultry is an important reservoir and source of human campylobacteriosis, although the contribution of other sources, reservoirs and transmission warrants more research. Clinical Microbiology and Infection (C) 2015 The Authors. Published by Elsevier Ltd on behalf of European Society of Clinical Microbiology and Infectious Diseases.
  • Pett, Helmi; Bradley, John; Okebe, Joseph; Dicko, Alassane; Tiono, Alfred B.; Goncalves, Bronner P.; Stone, Will; Chen, Ingrid; Lanke, Kjerstin; Neuvonen, Mikko; Mustaniemi, Anna-Liina; Eziefula, Alice C.; Gosling, Roly; D'Alessandro, Umberto; Drakeley, Chris; Niemi, Mikko; Bousema, Teun (2019)
    Single-dose primaquine (PQ) clears mature gametocytes and reduces the transmission of Plasmodium fakiparurn after artemisinin combination therapy. Genetic variation in CYP2D6, the gene producing the drug-metabolizing enzyme cytochrome P450 2D6 (CYP2D6), influences plasma concentrations of PQ and its metabolites and is associated with PQ treatment failure in Plasmodium vivax malaria. Using blood and saliva samples of varying quantity and quality from 8 clinical trials across Africa (n = 1,076), we were able to genotype CYP2D6 for 774 samples (72%). We determined whether genetic variation in CYP2D6 has implications for PQ efficacy in individuals with gametocytes at the time of PQ administration (n = 554) and for safety in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals treated with PQ (n = 110). Individuals with a genetically inferred CYP2D6 poor/intermediate metabolizer status had a higher gametocyte prevalence on day 7 or 10 after PQ than those with an extensive/ultrarapid CYP2D6 metabolizer status (odds ratio [OR] = 1.79 [95% confidence interval {CI}, 1.10, 2.90]; P = 0.018). The mean minimum hemoglobin concentrations during follow-up for G6PD-deficient individuals were 11.8 g/dl for CYP2D6 extensive/ultrarapid metabolizers and 12.1 g/dl for CYP2D6 poor/intermediate metabolizers (P = 0. 803). CYP2D6 genetically inferred metabolizer status was also not associated with anemia following PQ treatment (P = 0.331). We conclude that CYP2D6 poor/intermediate metabolizer status may be associated with prolonged gametocyte carriage after treatment with single-low-dose PQ but not with treatment safety.
  • Mull, Nathaniel; Jackson, Reilly; Sironen, Tarja; Forbes, Kristian M. (2020)
    The number of documented American orthohantaviruses has increased significantly over recent decades, but most fundamental research has remained focused on just two of them: Andes virus (ANDV) and Sin Nombre virus (SNV). The majority of American orthohantaviruses are known to cause disease in humans, and most of these pathogenic strains were not described prior to human cases, indicating the importance of understanding all members of the virus clade. In this review, we summarize information on the ecology of under-studied rodent-borne American orthohantaviruses to form general conclusions and highlight important gaps in knowledge. Information regarding the presence and genetic diversity of many orthohantaviruses throughout the distributional range of their hosts is minimal and would significantly benefit from virus isolations to indicate a reservoir role. Additionally, few studies have investigated the mechanisms underlying transmission routes and factors affecting the environmental persistence of orthohantaviruses, limiting our understanding of factors driving prevalence fluctuations. As landscapes continue to change, host ranges and human exposure to orthohantaviruses likely will as well. Research on the ecology of neglected orthohantaviruses is necessary for understanding both current and future threats to human health.
  • Ghafari, Mahan; Lumby, Casper K.; Weissman, Daniel B.; Illingworth, Christopher J. R. (2020)
    The transmission bottleneck is defined as the number of viral particles that transmit from one host to establish an infection in another. Genome sequence data have been used to evaluate the size of the transmission bottleneck between humans infected with the influenza virus; however, the methods used to make these estimates have some limitations. Specifically, viral allele frequencies, which form the basis of many calculations, may not fully capture a process which involves the transmission of entire viral genomes. Here, we set out a novel approach for inferring viral transmission bottlenecks; our method combines an algorithm for haplotype reconstruction with maximum likelihood methods for bottleneck inference. This approach allows for rapid calculation and performs well when applied to data from simulated transmission events; errors in the haplotype reconstruction step did not adversely affect inferences of the population bottleneck. Applied to data from a previous household transmission study of influenza A infection, we confirm the result that the majority of transmission events involve a small number of viruses, albeit with slightly looser bottlenecks being inferred, with between 1 and 13 particles transmitted in the majority of cases. While influenza A transmission involves a tight population bottleneck, the bottleneck is not so tight as to universally prevent the transmission of within-host viral diversity. IMPORTANCE Viral populations undergo a repeated cycle of within-host growth followed by transmission. Viral evolution is affected by each stage of this cycle. The number of viral particles transmitted from one host to another, known as the transmission bottleneck, is an important factor in determining how the evolutionary dynamics of the population play out, restricting the extent to which the evolved diversity of the population can be passed from one host to another. Previous study of viral sequence data has suggested that the transmission bottleneck size for influenza A transmission between human hosts is small. Reevaluating these data using a novel and improved method, we largely confirm this result, albeit that we infer a slightly higher bottleneck size in some cases, of between 1 and 13 virions. While a tight bottleneck operates in human influenza transmission, it is not extreme in nature; some diversity can be meaningfully retained between hosts.
  • Venkat, Vinaya (Helsingin yliopisto, 2021)
    The COVID-19 pandemic has brought into discussion the role of airborne transmission in infectious diseases. Many studies on enveloped viruses such as influenza suggest that respiratory viruses can be transmitted with large or small droplets formed when the patients talk, breathe, sneeze or cough. This comes under the category of direct contact. These droplets may also be transmitted indirectly as fomites through contact with contaminated surfaces. It has been difficult to prove that aerosols' transmission as the methods to capture virus in the air are not very sensitive. SARS-CoV-2 is a novel coronavirus affecting millions of people since 2019, and it has been challenging to contain the spread of this virus. Hence it is of vital importance to understand the transmission of the virus through aerosol and droplets. In this study, aerosol samples were collected from patients in the Surgical Hospital in Helsinki and patients at home in quarantine using various bioaerosols sampling devices like Biospot, Dekati, Button, and Andersen samplers, and passive sampling techniques to capture aerosols and droplets in the air. Such samples were subjected to cell culture on TMPRSS2 expressing Vero E6 cells to check for infectious viruses and RT-PCR using the N-gene targeting method to detect the presence of SARS-CoV-2 RNA in the samples. Out of the 32 saliva samples collected, 19 samples were tested positive by RT-PCR, but cell culture was not always positive. Bioaerosol samples collected using Dekati, Button, and Biospot samplers were negative by PCR. However, Andersen samplers showed positive results along with various passive aerosol samples collected on MEM, indicating aerosols' production of small sizes that can be transmitted air in the air to far distances and settling due to gravity. A relation between saliva samples and symptom days indicates the decrease in saliva viruses' infectivity with the prolonged infection as seen from the RT-PCR. From these findings, it can be concluded that SARS-CoV-2 can be spread by airborne and fomite transmission, and more so by patients with symptoms day 2-7 who are proven to be more infectious. Additionally, it was inferred that the Six Stage Andersen impactor would be the most efficient for aerosol sampling. Further studies are still needed to understand the characteristics of the spread and extent of infection caused by the variants of SARS-CoV-2.
  • Chen, Ingrid; Diawara, Halimatou; Mahamar, Almahamoudou; Sanogo, Koualy; Keita, Sekouba; Kone, Daouda; Diarra, Kalifa; Djimde, Mousse; Keita, Mohamed; Brown, Joelle; Roh, Michelle E.; Hwang, Jimee; Pett, Helmi; Murphy, Maxwell; Niemi, Mikko; Greenhouse, Bryan; Bousema, Teun; Gosling, Roly; Dicko, Alassane (2018)
    Methods: We conducted an open-label, nonrandomized, dose-adjustment trial of the safety of 3 single doses of primaquine in glucose-6-phosphate dehydrogenase (G6PD)-deficient adult males in Mali, followed by an assessment of safety in G6PD-deficient boys aged 11–17 years and those aged 5–10 years, including G6PD-normal control groups. The primary outcome was the greatest within-person percentage drop in hemoglobin concentration within 10 days after treatment. Results: Fifty-one participants were included in analysis. G6PD-deficient adult males received 0.40, 0.45, or 0.50 mg/kg of SLD-PQ. G6PD-deficient boys received 0.40 mg/kg of SLD-PQ. There was no evidence of symptomatic hemolysis, and adverse events considered related to study drug (n = 4) were mild. The mean largest within-person percentage change in hemoglobin level between days 0 and 10 was −9.7% (95% confidence interval [CI], −13.5% to −5.90%) in G6PD-deficient adults receiving 0.50 mg/kg of SLD-PQ, −11.5% (95% CI, −16.1% to −6.96%) in G6PD-deficient boys aged 11–17 years, and −9.61% (95% CI, −7.59% to −13.9%) in G6PD-deficient boys aged 5–10 years. The lowest hemoglobin concentration at any point during the study was 92 g/L. Conclusion: SLD-PQ doses between 0.40 and 0.50 mg/kg were well tolerated in G6PD-deficient males in Mali.
  • Järvelä, Aleksi; Tahtinen, Tero (2021)
    In this paper, we explore the historical background and the semantic underpinnings of a central, if marginally treated, metaphor of enlightenment and transmission in Chan discourse, "silent accord" . It features centrally in Essentials of the Transmission of Mind (sic)(sic)(sic), a text that gathers the teachings of Chan master Huangbo Xiyun (d. ca. 850), a major Tang dynasty figure. "Silent accord" is related to the concept of mind-to-mind transmission, which lies at the very core of Chan Buddhist self-understanding. However, Chan historiography has shown that this self-understanding was partially a product of the Song dynasty lineage records, historically retroactive syncretic constructs produced by monks and literati as efforts towards doctrinal and political recognition and orthodoxy. There are thus lacunae in the history of Chan thought opened up by the retrospective fictions of Song dynasty, and a lack of reliable, dateable documents from the preceding Tang dynasty era, possibly fraught with later additions. We situate the metaphor "silent accord" in the history of Chan thought by searching for its origins, mapping its functions in Chan literature, arguing for its influence and thereby its role in helping to bridge the ninth century gap.
  • Teinilä, Timo (Helsingfors universitet, 2009)
    The history of tractor in Finland is 100 years old and in the whole world 120 years old. Development of tractors is continually ongoing. During the first decades it concentrated on engines. The introduction of air-filled tyres made it possible to increase speed on the road, which in turn lead to an increase in the number of gears. Most of the inventions within transmissions were made during the 1950s. The first powershift gears, stepless hydrostatic transmissions, fuell-sell tractor, range-gear and the power shuttle were all introduced during this time. Over the next decades these features were improved and presented as new inventions. The hydrostatic-mechanical power split continuously variable transmission (CVT) has become more common in recent years, but the basic invention was already in use elsewhere during the 1910s. The first CVT tractor was the Fendt 926, which was launched in 1995. Later introductions came in 1999, when ZF’s Eccom and the S-Matic both came to the market. Of all the CVT tractors that were introduced to the market up until 2008, only the John Deere IVT ant the Valtra Direct machines were equipped with the manufacturer’s own diesel engines and CVT transmissions. All other CVT tractors were manufactured using five different transmissions and engines. In the coming years, several more transmissions and brands will appear on the market. Mechanical Torotraks and steel belt variators will be available for low-horsepower tractors in the sub-75 kW class. At the same time the number of brands seen in the CVT arena is increasing and the differences in the construction of stepless transmissions will grow. Current CVT transmissions differ from each greatly, with different functional principles, functionality and structure. Transmissions are divided into two main categories on the basis on functional principle, either summing up torque or summing up speed. The functionality division in mostly based on the hydrostatic part. In a full-CVT transmission, the percentage decrease of hydrostatic transmission has s linear relationship with the percentage increase in running speed. The function of the hydrostat in a semi-CVT transmission in to balance the speed differences between different gearing rations. In these transmissions the hydrostatic part of the transmission in around 20–40%. The percentage of hydrostatic transmission in double-CVT transmission varies with the driving speed. Double-CVT transmissions can have several driving speeds where the percentage of mechanical transmission is very close to 100%. The theoretical predictions about how common new features will become is based upon a study of four-wheel tractors in Western Europe and Finland. This can be precisely calculated using Logistic-funktion the result would be better if the source data covered a longer time period. The regular S-curve depicts how common the new features will become in tractors of the future. The real growth area is during the period when the market share of 4wd tractors increase from 10 to 90 %. This shows that the annual growth in Western Europe was 4,0% and in Finland 7,5%. Within the next few years it will become necessary to study further new entrants of the CVT transmission market and to make predictions more precise by means of increasing the amount of source data. The users driving with conventional transmissions could utilise the driving strategies of CVT transmissions. Tractor manufacturers should ensure that their customers are fully educated in the use of their new machines, in order that they develop the correct driving habits. This in an important part of postmarketing strategy.
  • Hofstra, L. Marije; Sauvageot, Nicolas; Albert, Jan; Alexiev, Ivailo; Garcia, Federico; Struck, Daniel; Van de Vijver, David A. M. C.; Asjo, Birgitta; Beshkov, Danail; Coughlan, Suzie; Descamps, Diane; Griskevicius, Algirdas; Hamouda, Osamah; Horban, Andrzej; Van Kasteren, Marjo; Kolupajeva, Tatjana; Kostrikis, Leondios G.; Liitsola, Kirsi; Linka, Marek; Mor, Orna; Nielsen, Claus; Otelea, Dan; Paraskevis, Dimitrios; Paredes, Roger; Poljak, Mario; Puchhammer-Stoeckl, Elisabeth; Sonnerborg, Anders; Stanekova, Danica; Stanojevic, Maja; Van Laethem, Kristel; Zazzi, Maurizio; Lepej, Snjezana Zidovec; Boucher, Charles A. B.; Schmit, Jean-Claude; Wensing, Annemarie M. J.; SPREAD Program; Ristola, M. (2016)
    Background. Numerous studies have shown that baseline drug resistance patterns may influence the outcome of antiretroviral therapy. Therefore, guidelines recommend drug resistance testing to guide the choice of initial regimen. In addition to optimizing individual patient management, these baseline resistance data enable transmitted drug resistance (TDR) to be surveyed for public health purposes. The SPREAD program systematically collects data to gain insight into TDR occurring in Europe since 2001. Methods. Demographic, clinical, and virological data from 4140 antiretroviral-naive human immunodeficiency virus (HIV)-infected individuals from 26 countries who were newly diagnosed between 2008 and 2010 were analyzed. Evidence of TDR was defined using the WHO list for surveillance of drug resistance mutations. Prevalence of TDR was assessed over time by comparing the results to SPREAD data from 2002 to 2007. Baseline susceptibility to antiretroviral drugs was predicted using the Stanford HIVdb program version 7.0. Results. The overall prevalence of TDR did not change significantly over time and was 8.3% (95% confidence interval, 7.2%-9.5%) in 2008-2010. The most frequent indicators of TDR were nucleoside reverse transcriptase inhibitor (NRTI) mutations (4.5%), followed by nonnucleoside reverse transcriptase inhibitor (NNRTI) mutations (2.9%) and protease inhibitor mutations (2.0%). Baseline mutations were most predictive of reduced susceptibility to initial NNRTI-based regimens: 4.5% and 6.5% of patient isolates were predicted to have resistance to regimens containing efavirenz or rilpivirine, respectively, independent of current NRTI backbones. Conclusions. Although TDR was highest for NRTIs, the impact of baseline drug resistance patterns on susceptibility was largest for NNRTIs. The prevalence of TDR assessed by epidemiological surveys does not clearly indicate to what degree susceptibility to different drug classes is affected.