Dynamic of SARS-CoV-2 spread in Bulgaria, 2020-2022

The COVID-19 pandemic is associated with high morbidity and significant mortality worldwide. The objective of this study was to track the circulation pattern of SARS-CoV-2 in Bulgaria over three consecutive years (2020-2022) and to analyze the involvement of SARS-CoV-2 in cases of co-infections. A total of 98 247 clinical samples were tested for SARS-CoV-2 using a Real-Time RT-PCR method and 25.2% of them were positive. The positive rate for SARS-CoV-2 was greater among hospitalized patients compared to outpatients (p<0.05). Approximately 48.3% of all SARS-CoV-2-positive cases were male and 51.7% were female (p<0.05). SARS-CoV-2 positivity was highest in the group of oldest adults (≥65 years) (average 40.6%), and lowest in the group of youngest children (0-5 years) (average 9.4%). Several peaks in the spread of SARS-CoV-2 infections were observed. Among the 1 463 SARS-CoV-2 positive clinical samples examined for the presence of other respiratory viruses, 109 (7.5%) cases of co-infections were found. The greatest variety of co-infections with SARS-CoV-2 and other respiratory viruses was detected during the Omicron wave. Surveillance of SARS-CoV-2 is important to continue in the future in order not to miss the emergence of new genetic variants with increased infectivity, virulence or immune escape

Global disparities in SARS-CoV-2 genomic surveillance

Genomic sequencing is essential to track the evolution and spread of SARS-CoV-2, optimize molecular tests, treatments, vaccines, and guide public health responses. To investigate the global SARS-CoV-2 genomic surveillance, we used sequences shared via GISAID to estimate the impact of sequencing intensity and turnaround times on variant detection in 189 countries. In the first two years of the pandemic, 78% of high-income countries sequenced >0.5% of their COVID-19 cases, while 42% of low- and middle-income countries reached that mark. Around 25% of the genomes from high income countries were submitted within 21 days, a pattern observed in 5% of the genomes from low- and middle-income countries. We found that sequencing around 0.5% of the cases, with a turnaround time <21 days, could provide a benchmark for SARS-CoV-2 genomic surveillance. Socioeconomic inequalities undermine the global pandemic preparedness, and efforts must be made to support low- and middle-income countries improve their local sequencing capacity