Bacterial and Viral Co-Infections in COVID-19 Patients: Etiology and Clinical Impact.

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.

Resurgence of influenza with increased genetic diversity of circulating viruses during the 2022-2023 season.

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.

Prevalence and clinical impact of mono- and co-infections with endemic coronaviruses 229E, OC43, NL63, and HKU-1 during the COVID-19 pandemic.

Introduction: Endemic human coronaviruses (eHCoVs) are found worldwide and usually result in mild to moderate upper respiratory tract infections. They can lead to more severe illnesses such as croup, bronchiolitis, and pneumonia in vulnerable populations. During the coronavirus disease 2019 (COVID-19) pandemic, information on HCoV prevalence and incidence and clinical impact of co-infections of HCoV with SARS-CoV-2 was lacking.

Severe SARS-CoV-2 and respiratory syncytial virus co-infection in two children.

The Coronavirus Disease 2019 (COVID-19) caused by a novel coronavirus (SARS-CoV-2) affects mainly older adults. Those with comorbidities are at a higher risk of severe disease and even death. The symptomatic infection rate of children is lower, manifestations are milder, and severe forms are scarce.

Genomic Epidemiology and Lineage Dynamics of SARS-CoV-2 in Bulgaria: Insights from a Three-Year Pandemic Analysis.

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.

Early Detection of the Recombinant SARS-CoV-2 XAN Variant in Bulgaria: Initial Genomic Insights into Yet Another Piece of the Growing Puzzle of Recombinant Clades.

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.

Rhinovirus Genotypes Circulating in Bulgaria, 2018-2021.

Rhinoviruses (RV) are one of the most common causative agents of respiratory infections, with significant socioeconomic impact. RV infections are not notifiable in Bulgaria, and little is known about the different RV genotypes circulating in the country. This study aims to investigate the diversity of RV genotypes that were circulating in Bulgaria in the period 2018-2021 in samples from ILI/ARI patients.

Low prevalence of influenza viruses and predominance of A(H3N2) virus with respect to SARS-CoV-2 during the 2021-2022 season in Bulgaria.

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.

Periostin and IFN-γ levels in serum and nasopharyngeal aspirate in infants with viral-induced wheezing - 2 year follow-up.

Background: The present study assesses the immune response in children with viral-induced wheezing by examining the two factors-interferon-gamma (IFN-γ) and periostin in serum and nasopharyngeal aspirate (NPA). The aim was to find a pattern with the severity and frequency of wheezing episodes.

Methods: Sixty-nine infants (40 boys and 29 girls), with a mean age of 11.

Clinical significance and role of coinfections with respiratory pathogens among individuals with confirmed severe acute respiratory syndrome coronavirus-2 infection.

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).

Initial introduction and spread of the SARS-CoV-2 AY.4.2.1 Delta variant in Bulgaria, a genomic insight.

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.

Prevalence and Genetic Characteristics of Human Bocaviruses Detected in Patients with Acute Respiratory Infections in Bulgaria.

Нuman bocaviruses (hBoVs) are often associated with acute respiratory infections (ARIs). Information on the distribution and molecular epidemiology of hBoVs in Bulgaria is currently limited. The objectives of this study were to investigate the prevalence and genetic characteristics of hBoVs detected in patients with ARIs in Bulgaria.

The Prevalence and Genetic Characterization of Human Metapneumovirus in Bulgaria, 2016-2019.

Introduction: We investigated the prevalence of human metapneumovirus (hMPV) among patients with acute respiratory infections in Bulgaria, and performed genetic characterization of the F gene of these strains.

Methods: Nasopharyngeal swabs collected from patients of a range of ages were tested by using real-time PCR for 12 respiratory viruses. The F gene was sequenced, and phylogenetic and amino acid analyses of the F gene/protein were performed.

Genetic characterisation of the influenza viruses circulating in Bulgaria during the 2019-2020 winter season.

Influenza viruses have a high potential for genetic changes. The objectives of this study were to analyse influenza virus circulation in Bulgaria during the 2019/2020 season, to perform a phylogenetic and molecular analyses of the haemagglutinin (HA) and neuraminidase (NA) sequences of representative influenza strains, and to identify amino acid substitutions compared to the current vaccine strains. Seasonal influenza viruses A(H3N2), A(H1N1)pdm09 and B/Victoria-lineage were detected using a real-time RT-PCR in 323 (23.

Predominance of ON1 and BA9 genotypes of respiratory syncytial virus (RSV) in Bulgaria, 2016-2018.

The objectives of this study were to investigate the prevalence of respiratory syncytial virus (RSV) infections in Bulgaria, to characterize the genetic diversity of the RSV strains, and to perform amino acid sequence analysis of the RSV G protein. Clinical, epidemiological data and nasopharyngeal swabs were prospectively collected from children aged less than 5 years presenting with acute respiratory infections from October 2016 to September 2018. Real-time polymerase chain reaction for 12 respiratory viruses, and sequencing, phylogenetic, and amino acid analyses of the RSV G gene/protein were performed.

"Are changes in breast density during the menstrual cycle relevant? To what?".

Purpose: Cancers can be hidden by high breast density (BDen)- the masking effect (ME). BDen is also a modifiable and highly prevalent breast cancer risk (BCR) factor. The purposes of this study were to determine how much glandular volume (GVol), breast volume (BVol) and their ratio: BDen change during the menstrual cycle, and if these changes could affect ME or be relevant to results of interventional studies aiming to diminish BCR using these parameters as surrogates.

Genetic diversity of influenza A viruses circulating in Bulgaria during the 2018-2019 winter season.

Influenza viruses evolve rapidly and change their antigenic characteristics, necessitating biannual updates of flu vaccines. The aim of this study was to characterize influenza viruses circulating in Bulgaria during the 2018/2019 season and to identify amino acid substitutions in them that might impact vaccine effectiveness. Typing/subtyping of influenza viruses were performed using real-time Reverse Transcription-PCR (RT-PCR) and results of phylogenetic and amino acid sequence analyses of influenza strains are presented.

Predominance of influenza B/Yamagata lineage viruses in Bulgaria during the 2017/2018 season.

In this study, we investigated the antigenic and genetic characteristics of influenza viruses circulating in Bulgaria during the 2017/2018 season. The detection and typing/subtyping of influenza viruses were performed using real-time RT-PCR. Results of antigenic characterisation, phylogenetic and amino acid sequence analyses of representative influenza strains are presented.

Viral pathogens associated with acute lower respiratory tract infections in children younger than 5 years of age in Bulgaria.

Acute lower respiratory infections (ALRIs) are a leading cause of morbidity and hospital admissions in children. This study aimed to determine the viral etiology of these infections in children aged < 5 years during three successive epidemic seasons in Bulgaria. Nasopharyngeal and throat specimens were collected from children with bronchiolitis and pneumonia during the 2015/2016, 2016/2017, and 2017/2018 seasons.

Predominance of influenza A(H3N2) viruses during the 2016/2017 season in Bulgaria.

Purpose: Influenza viruses are characterised by high variability, which makes them able to cause annual epidemics. The aim of this study is to determine the antigenic and genetic characteristics of influenza viruses circulating in Bulgaria during the 2016/2017 season.

Methodology: The detection and typing/subtyping of influenza viruses were performed using real time RT-PCR.

Prevalence and genetic characterisation of respiratory syncytial viruses circulating in Bulgaria during the 2014/15 and 2015/16 winter seasons.

The respiratory syncytial virus (RSV) is a leading cause of acute respiratory illnesses (ARI) in infants and young children. The objectives of this study were to investigate the RSV circulation among children aged <5 years in Bulgaria, to identify the RSV-A and RSV-B genotypes and to perform an amino acid sequence analysis of second hypervariable region (HVR2) of the G gene. During the 2014/15 and 2015/16 winter seasons, nasopharyngeal specimens of 610 children aged <5 years with ARI were tested using Real Time RT-PCR for influenza viruses, RSV, metapneumovirus, parainfluenza viruses, rhinoviruses and adenoviruses.