Human adenovirus 7 is a non‑enveloped double‑stranded DNA virus classified within species B of the genus Mastadenovirus. Its virion has an icosahedral capsid about 70–90 nm in diameter and a linear genome anchored to terminal proteins. Type 7 is notable for causing severe acute respiratory disease and pneumonia, particularly in children and institutional settings.
Biology and pathogenesis
Adenoviruses comprise more than a hundred antigenically distinct types grouped into species A–G. HAdV‑7 belongs to species B and exhibits a strong tropism for the respiratory epithelium. Transmission occurs via respiratory droplets and contaminated surfaces. After binding to cell receptors, the virus enters by endocytosis and uncoats, delivering its genome to the nucleus where replication and assembly take place. The infection is often productive, but adenoviruses can persist in lymphoid tissues such as the tonsils. Host defence relies on neutralising antibodies and cytotoxic T cells.
Clinical features and notable facts
HAdV‑7 is among the adenovirus types most commonly associated with serious respiratory illness. Outbreaks in hospitals, childcare centres and military training camps have resulted in high rates of pneumonia and even fatalities. In addition to high fever, cough and pharyngitis, patients may develop severe lower respiratory tract disease requiring hospitalisation. A live oral vaccine containing types 4 and 7 is used to protect military recruits and has markedly reduced illness. Compared with type 4, HAdV‑7 tends to cause more severe disease; compared with type 14, which is an emerging serotype associated with outbreaks, type 7 is more established but remains a major cause of morbidity. It does not commonly cause keratoconjunctivitis or gastroenteritis. Because HAdV‑7 can produce significant morbidity and mortality, especially in vulnerable populations, surveillance and vaccination strategies are important in high‑risk settings. Improved hygiene and isolation during outbreaks can mitigate spread. Natural infection generally confers long‑lasting immunity. Related Terms: Human Adenovirus 3, Human Adenovirus 21, Human Adenovirus 14, Adenovirus vaccine