Patients with COVID-19 infection have distinct oropharyngeal microbiota composition and diversity metrics according to disease severity. However, these findings are not consistent across the literature. We conducted a multicenter, prospective study in patients with COVID-19 requiring outpatient versus inpatient management to explore the microbial abundance of taxa at the phylum, family, genus, and species level, and we utilized alpha and beta diversity indices to further describe our findings. We collected oropharyngeal washing specimens at the time of study entry, which coincided with the COVID-19 diagnosis, to conduct all analyses. We included 43 patients in the study, of whom 16 were managed as outpatients and 27 required hospitalization. Proteobacteria, Actinobacteria, Bacteroidetes, Saccharibacteria TM7, Fusobacteria, and Spirochaetes were the most abundant phyla among patients, while 61 different families were detected, of which the Streptococcaceae and Staphylococcaceae families were the most predominant. A total of 132 microbial genera were detected, with Streptococcus being the predominant genus in outpatients, in contrast to hospitalized patients, in whom the Staphylococcus genus was predominant. LeFSe analysis identified 57 microbial species in the oropharyngeal washings of study participants that could discriminate the severity of symptoms of COVID-19 infections. Alpha diversity analysis did not reveal a difference in the abundance of bacterial species between the groups, but beta diversity analysis established distinct microbial communities between inpatients and outpatients. Our study provides information on the complex association between the oropharyngeal microbiota and SARS-CoV-2 infection. Although our study cannot establish causation, knowledge of specific taxonomic changes with increasing SARS-CoV-2 infection severity can provide us with novel clues for the prognostic classification of COVID-19 patients.

Parvovirus B19 is a DNA virus. Most parvoviruses infect animals; Parvovirus B19 infects humans. Parvovirus B19 is mainly transmitted through respiratory droplets during close contact, but additional routes such as transmission through contaminated blood products and vertical transmission from mother to fetus have also been documented. Infections occur throughout the year, with a seasonal increase between late winter and early summer. Clinical symptoms depend on age, and on patients’ immune status. Healthy, immunocompetent individuals experience asymptomatic or mild infections including a febrile rash; serious complications rarely appear, such as rheumatoid-like arthritis or acute myocarditis. Clusters of myocarditis cases following Parvovirus B19 infections appeared in a daycare in Thessaloniki in 2024. To molecularly and phylogenetically characterize Parvovirus B19 strains detected during a pediatric outbreak associated with elevated troponin levels and myocarditis in Northern Greece, and to compare these strains with isolates from adult cases with mild symptoms in order to explore potential associations between viral genetic variability and cardiac involvement. MinION sequencing protocol was performed for nine whole blood samples, seven belonging to children with myocarditis, and two to adults presenting mild symptoms. Statistical analysis was performed with QualiMap 2.3 and relevant tools. Phylogenetic analysis identified distinct viral groups originating from the samples investigated. A distinct branch was formed by the reference genome and the ones of the adults’ samples, while samples from children with myocarditis provided discrete branches differing from the reference one. The findings demonstrate a clear association between Parvovirus B19 infection and myocarditis in the pediatric cases analyzed. The detected viral strains, including variants identified in several samples, support the role of Parvovirus B19 as a contributing factor in post-infectious cardiac involvement. Although these results reinforce the clinical relevance of Parvovirus B19 in childhood myocarditis, expanding the sample size would allow for a more robust characterization of circulating strains and confirmation of the observed patterns.