Low prevalence of influenza viruses and predominance of A(H3N2) virus with respect to SARS-CoV-2 during the 2021-2022 season in Bulgaria.
J Med Virol
; 95(2): e28489, 2023 02.
Article
in English
| MEDLINE | ID: covidwho-2267040
ABSTRACT
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 (4.2%) of the 2193 patients with acute respiratory illness tested wherein all detected viruses were subtyped as A(H3N2). SARS-CoV-2 was identified in 377 (24.3%) of the 1552 patients tested. Significant differences in the incidence of influenza viruses and SARS-CoV-2 were found between individual age groups, outpatients/inpatients, and in the seasonal distribution of cases. Two cases of coinfections were identified. In hospitalized patients, the Ct values of influenza viruses at admission were lower in adults aged ≥65 years (indicating higher viral load) than in children aged 0-14 years (p < 0.05). In SARS-CoV-2-positive inpatients, this association was not statistically significant. HA genes of all A(H3N2) viruses analyzed belonged to subclade 3C.2a1b.2a. The sequenced viruses carried 11 substitutions in HA and 5 in NA, in comparison to the vaccine virus A/Cambodia/e0826360/2020, including several substitutions in the HA antigenic sites B and C. This study revealed extensive changes in the typical epidemiology of influenza infection, including a dramatic reduction in the number of cases, diminished genetic diversity of circulating viruses, changes in age, and seasonal distribution of cases.
Keywords
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Main subject:
Influenza Vaccines
/
Influenza, Human
/
COVID-19
Type of study:
Experimental Studies
/
Observational study
/
Randomized controlled trials
Topics:
Vaccines
Limits:
Adult
/
Child
/
Humans
Country/Region as subject:
Europa
Language:
English
Journal:
J Med Virol
Year:
2023
Document Type:
Article
Affiliation country:
Jmv.28489
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