Publications by authors named "Iva Christova"

Background: Mixed infections can worsen disease symptoms. This study investigated the impact of mixed infections with viral and bacterial pathogens in patients positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods: Using the in-house multiplex PCR method, we tested 337 SARS-CoV-2 positive samples for co-infections with three bacterial and 14 other viral pathogens.

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  • Acquired 16S rRNA methyltransferases (16S-RMTases) enable high resistance to aminoglycosides and are linked to resistance against other antibiotics like β-lactams and quinolones.
  • A study conducted on over 10,000 bacterial isolates from 2006 to 2023 found that 1.4% of them carried various methyltransferase genes alongside other significant resistance genes.
  • The research highlighted the diverse origins of these resistance genes in different plasmids and indicated that their ability to acquire more resistance genes poses a significant long-term public health risk.
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Toscana virus (TOSV) is an arthropod-borne virus transmitted by sandflies and is mainly found in countries around the Mediterranean basin. In this article, we present the findings of a seroprevalence study on TOSV in Bulgaria. We aim to assess the current epidemiological situation regarding TOSV in the country and raise clinical awareness.

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  • Lyme Borreliose (LB) is a tick-borne infection that is becoming more common in Bulgaria, identified as the leading tick-borne disease in the area.
  • A study analyzed 1,892 serum samples to determine the seroprevalence of LB, finding an overall rate of 5.4%, with variations influenced by factors like age, sex, and whether individuals live in rural or urban settings.
  • The results showed higher seroprevalence in older adults (8.4% in those over 65), males (8.4%), and rural residents (10.2%), emphasizing the need for better diagnostic methods and public health awareness in combating LB.
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: Monkeypox (mpox) is currently the most common orthopoxvirus (OPXV) zoonotic disease, and, since 2022, there has been atypical person-to-person transmission observed in non-endemic countries. The present study aimed to investigate the frequency of monkeypox virus (MPXV) and OPXV DNA detection in recommended and alternative clinical materials taken during the acute and convalescent phases of infection in Bulgarian patients. : The study included laboratory investigation by real time PCR of 181 clinical samples from 42 Bulgarian patients with possible mpox infections.

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After two seasons of absence and low circulation, influenza activity increased significantly in the winter of 2022-2023. This study aims to characterize virological and epidemiological aspects of influenza infection in Bulgaria during the 2022-2023 season and perform a phylogenetic/molecular analysis of the hemagglutinin () and neuraminidase () sequences of representative influenza strains. Influenza A and B viruses generate new genetic groups/clades each season, replacing previously circulating variants.

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  • - During summer 2023, Europe saw a small uptick in mpox cases after a major outbreak in 2022, marked by peaks happening at different times in various countries!* - The demographic makeup of the new cases was similar to those from previous reports, maintaining the same trends.
  • - All collected case sequences from this recent resurgence belonged to clade IIb, highlighting the need for ongoing control efforts to eliminate mpox in the region.
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  • * Seasonal respiratory viruses were detected using multiplex PCR and next-generation sequencing, highlighting the highest coinfection rate (15%) in patients 16 years and younger.
  • * Whole-genome sequencing revealed various genetic groups among the detected viruses and multiple amino acid substitutions, emphasizing the need for understanding viral interactions for effective treatment and prevention strategies.
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  • Carbapenemase-producing Enterobacteriaceae, specifically the ESCPM group, are increasingly recognized as major causes of hospital-acquired infections but lack systematic genomic tracking.
  • A study analyzed 36 clinical isolates from Bulgaria, identifying various carbapenemase genes, with NDM-1 and VIM-4 being the most common.
  • The majority of these resistance genes were found on self-conjugative plasmids, indicating a high potential for gene transfer and reinforcing the need for better infection control protocols.
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  • Respiratory syncytial virus (RSV) is a significant cause of respiratory infections, and a study in Bulgaria aimed to assess its prevalence and genetic diversity alongside other viruses from 2020 to 2023.
  • Out of 3,047 patients with respiratory issues, 59.5% tested positive for viral pathogens, with RSV being the second most common at 10.9%, especially affecting children under 5 years old.
  • The research found a marked increase in RSV cases in the 2022-2023 season, with specific genetic strains identified, indicating a resurgence post-COVID-19 restrictions.
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The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has brought about significant challenges worldwide. In this study, we present a comprehensive analysis of the genomic epidemiology and lineage dynamics of SARS-CoV-2 in Bulgaria over a three-year period. Through extensive genomic sequencing and data analysis, we investigated the evolution of the virus, the emergence of variants of concern (VOCs), and their impact on the country's pandemic trajectory.

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The first recombinant SARS-CoV-2 variants were identified in 2022, causing public health concerns. The importance of recombinant variants has increased especially since the WHO designated the recombinant variant XBB and its lineages as subvariants that require monitoring on 20 November 2022. In this study, we provide the first insights into the new SARS-CoV-2 variant named XAN, a recombinant composed of Omicron sub-lineages BA.

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The prevalence of hepatitis E virus (HEV) in the Bulgarian population remains underestimated. The aim of the present study was to evaluate age and gender trends in HEV prevalence in the heterogeneous Bulgarian population. Stored serum samples from blood donors and different patient sub-populations-kidney recipients (KR), patients with Guillain-Barre syndrome (GBS), Lyme disease (LD), patients with liver involvement and a clinical diagnosis other than viral hepatitis A and E (non-AE), hemodialysis (HD) and HIV-positive patients (HIV)-were retrospectively investigated for markers of past and recent/ongoing HEV infection.

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  • Mpox is a zoonotic disease due to the Mpox virus, which was first noted outside its typical regions in Central and West Africa on May 21, 2022.
  • A study involving 647 patients across 16 countries found the majority of cases were young males, mostly homosexual-bisexual, with symptoms like rashes, fever, and lymphadenopathy.
  • The findings highlight the need for increased awareness and swift public health responses to manage Mpox’s spread beyond endemic regions.
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Objectives: Cytokine dysregulation has been proposed as one of the main culprits for severe COVID-19 and poor prognosis. We examined the parallel presence of lymphopoietic, proinflammatory, Th1, Th2, regulatory cytokines, and chemokines in the serum of 47 patients with mild, moderate, and severe COVID-19 and evaluated the association between cytokine concentrations and disease severity.

Methods: A multiplex quantitative cytokine analysis ProcartaPlex™ immunoassay was applied, using the Luminex 200X detection system (Invitrogen).

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Social distancing, mask-wearing, and travel restrictions during the COVID-19 pandemic have significantly impacted the spread of influenza viruses. The objectives of this study were to analyze the pattern of influenza virus circulation with respect to that of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Bulgaria during the 2021-2022 season and to perform a phylogenetic/molecular analysis of the hemagglutinin (HA) and neuraminidase (NA) sequences of representative influenza strains. Influenza infection was confirmed using real-time reverse transcription polymerase chain reaction in 93 (4.

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Introduction: This study aimed to determine the prevalence, viral profile, and clinical features of coinfections with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and other respiratory viruses.

Methods: Nasopharyngeal samples and clinical data of 221 hospitalized patients and 21 outpatients were collected and analyzed. Real-time reverse transcription-polymerase chain reaction was used to detect SARS-CoV-2, influenza virus, respiratory syncytial virus (RSV), human metapneumovirus (HMPV), parainfluenza virus (PIV) 1,2,3, rhinovirus (RV), adenovirus (AdV), bocaviruses (BoV), and seasonal coronaviruses (OC43, 229E, NL63, and HKU1).

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The evolution of the emerging SARS-CoV-2 variants carrying mutations in the spike protein raises concerns about the possibility of accelerated transmission in the ever-evolving COVID-19 pandemic worldwide. AY.4.

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Installing efficient protective immunity by anti-SARS-CoV-2 vaccines is the only current means to overcome coronavirus disease 2019 pandemics. The cellular and humoral immune responses induced with an messenger RNA (mRNA) (BNT162b2) or with a vector (ChAdOx1nCoV-19) vaccine among Bulgarian healthcare workers (n = 123, aged 23-71 years) were studied in the course of 16 weeks after priming. Receptor-binding domain (RBD)-blocking Abs and SARS-CoV-2 RBD immunoglobulin A  (IgA) were evaluated in parallel with interferon gamma (IFNγ)-producing virus-specific T cells.

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Freely available healthcare, universally accessible to the population of citizens, is a key ideal for European welfare systems. As labor migration of the twentieth century gave way to the globalized streams of the twenty-first century, new challenges to fulfilling these ideals have emerged. The principle of freedom of movement, together with large-scale forced migration have led to large scale movements of people, making new demands on European healthcare systems which had previously been largely focused on meeting sedentary local populations' needs.

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West Nile fever (WNF) is a vector-borne infection caused by a Flavivirus-West Nile virus (WNV). WNV is transmitted by mosquitoes, and birds are the major natural reservoir. A recent increase in the number of the WNF cases has been reported in Europe, the Balkans, and Bulgaria.

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We are living in times where a viral disease has brought normal life in much of the world to a halt. The novel coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 2019 (COVID-19) started in December 2019 in Wuhan, China initially and in a short time crossed the European borders. After mitigating the epidemic in China, Italy became one of the most COVID-19 affected countries worldwide.

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Background: West Nile virus (WNV) lineage 2, and especially the Hungarian clade, predominates in Europe. Most of the Hungarian clade strains cluster into 2 groups: Central/South-West European and Balkan.

Objectives: Since there was not any study on WNV in mosquitoes in Bulgaria, the present study was designed to test Culex spp.

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We illustrate the potential for specialist laboratory networks to be used as preparedness and response tool through rapid collection and sharing of data. Here, the Emerging Viral Diseases-Expert Laboratory Network (EVD-LabNet) and a laboratory assessment of chikungunya virus (CHIKV) in returning European travellers related to an ongoing outbreak in Thailand was used for this purpose. EVD-LabNet rapidly collected data on laboratory requests, diagnosed CHIKV imported cases and sequences generated, and shared among its members and with the European Centre for Disease Prevention and Control.

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A case of a 66-year-old man with West Nile neuroinvassive disease manifested with fever, weakness, fatigue, consciousness disorders and underlying diabetes mellitus type 2 and cardiovascular diseases is presented. Laboratory data showed elevated erythrocyte sedimentation rate and fibrinogen. Serological tests revealed West Nile virus specific antibodies of class IgM and IgG in serum.

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