Abstract:
Relevance. SARS-CoV-2 infection remains a major public health challenge because of the
continuing evolution of the virus and the emergence of genetic variants that affect transmission
and disease control. Genomic monitoring is essential for epidemiological surveillance and for
identifying circulating variants.
Aim of the study. To identify SARS-CoV-2 variants circulating in the Republic of Moldova
and to perform phylogenetic analysis of the detected isolates, with the aim of improving COVID19 surveillance and morbidity control measures.
Objectives of the study. To provide a phylogenetic characterization of SARS-CoV-2
isolates detected in the Republic of Moldova; to study SARS-CoV-2 evolution by identifying
substitutions, insertions, and deletions and comparing them with global viral genome diversity; to
analyze SARS-CoV-2 circulation dynamics and the emergence of new genetic variants, including
the relationship between viral genotypes and epidemiological data; to assess wastewater
monitoring as a method for predicting epidemiological trends in SARS-CoV-2 infection; and to
evaluate the impact of different SARS-CoV-2 genotypes in order to support proposals for
improving the laboratory diagnosis of COVID-19.
Scientific novelty and originality. Original data on the genotypic and phenotypic
characteristics of SARS-CoV-2 circulating in the Republic of Moldova were obtained for the first
time using modern genomic sequencing and bioinformatic analysis. The study identified SARSCoV-2 genovariants in clinical and wastewater samples, assessed their position within global
phylogenetic trees, and analyzed the molecular evolution of the virus. The findings contributed to
forecasting epidemic dynamics and optimizing surveillance and control measures for COVID-19.
The obtained study results. The research determined the genetic structure and distribution
of SARS-CoV-2 lineages in the Republic of Moldova during 2021–2025. Dominant mutations
were identified, and their impact on the biological properties of the virus was assessed. The study
also demonstrated the value of wastewater monitoring for early detection of circulating variants,
evaluated the performance of bioinformatic tools used for sequencing-data analysis, and developed
proposals for improving laboratory diagnosis and epidemiological surveillance.
Theoretical background. The study deepens current understanding of the molecular
evolution of SARS-CoV-2 and the mechanisms of viral adaptation, providing a scientific basis for
the development of modern genomic surveillance and epidemiological management strategies.
The research practical value. The findings were applied through the development of goodpractice guidelines in genomic sequencing, the update of the national clinical protocol, and the
integration of the data into the training of students, resident physicians, and specialists in the field.
Implementation of scientific results. The research findings were implemented through the
development of a guide on metagenomic sequencing, preparation of a monograph on nucleic acid
sequencing, update of the National Clinical Protocol on COVID-19, and use of the results in
healthcare institutions, epidemiological surveillance, and university education.
PhD thesis structure. The thesis includes an introduction, four chapters, general
conclusions and recommendations, a bibliography of 189 references, 12 annexes, 94 pages of main
text, 8 tables, and 42 figures. The results have been published in 32 scientific papers.
Keywords: COVID-19; SARS-CoV-2; sequencing; NGS; viral genome; genetic
monitoring; mutation variants; wastewater.
