Increased circulation of human adenovirus in 2023: an investigation of the circulating genotypes, upper respiratory viral loads, and hospital admissions in a large academic medical center

An increase in the circulation of human adenoviruses (HAdV) in 2023 was notable. HAdV genotypes circulating were characterized. Viral loads, clinical presentations, and outcomes were associated with the genotypes. Remnant respiratory samples positive for HAdV after standard-of-care testing at the Johns Hopkins Microbiology laboratory (N = 270) were collected for genotyping by next-generation sequencing of the hexon gene. HAdV loads in respiratory samples were assessed using droplet digital PCR. The association between predominant genotypes, outcomes, and viral loads was evaluated. Of a total of 249 samples with characterized HAdV genotypes, 179 (71.9%) were genotype B3. HAdV-B3 was associated with a statistically significant increase in viral loads in respiratory samples, specifically in patients 5 years and younger. Patients infected with HAdV-B3 were primarily in the age group 3–5 years in contrast to patients infected with non-B3 genotypes who were younger than 3 years. Strict criteria for defining HAdV-related admission identified a hospitalization rate of 14.8%. Infections with HAdV-B3 were not associated with an increased likelihood of HAdV-related admissions. The circulation of HAdV-B3 in 2023 after at least 2 years of reduced detection likely contributed to the increased number of cases.