Genetic analysis of human adenovirus type 7 circulating in China during 2014-2025.

OBJECTIVES

Human adenovirus type 7 (HAdV-7) has caused outbreaks of acute respiratory infections (ARIs) among children in multiple countries. This study aimed to investigate the clinical and genetic characteristics of HAdV-7 in hospitalized children with ARIs in China.

METHODS

Respiratory samples were collected from hospitalized children with ARIs at 10 hospitals across Northern and Southern China between 2014 and 2025 for HAdV detection and genotyping. Clinical data of HAdV-7-positive patients were collected for clinical characteristics analysis. The whole genomes of isolated HAdV-7 strains were sequenced for bioinformatics analysis with those selected from GenBank.

RESULTS

Among 250 HAdV-positive samples, 79 (31.60%) were HAdV-7, ranking second only to HAdV-114 (46.80%). Patients primarily presented with fever, cough, and sputum production. Some cases also complicated with gastrointestinal and neurological symptoms, skin rashes, and ocular diseases. Severe pneumonia occurred in 54.43% of patients, with one death. Whole genome sequence phylogenetic analysis revealed that HAdV-7 could be divided into two clusters. Cluster 1, including the prototype strain, had been rarely reported globally since the discovery of HAdV-7. Cluster 2 was the predominant cluster circulating worldwide, including China. Three novel amino acid substitutions were observed in the Loop 1 region of the Hexon protein, which might be associated with the severe disease phenotype and resulted in the emergence of a positive selection site. Recombination analysis identified a recombination event, which occurred as early as 1988. In vitro experiments demonstrated that HAdV-7 had comparable proliferation capacity with other genotypes of the HAdV-B species.

CONCLUSIONS

HAdV-7 was an important pathogen of hospitalized children with ARIs in China, and associated with severe diseases and even death. Cluster 2 was the predominant epidemic cluster worldwide. Although the HAdV-7 genome was relatively conserved and stable, novel amino acid mutations have occurred.