Human adenovirus 1 is a non‑enveloped double‑stranded DNA virus belonging to the genus Mastadenovirus. It has an icosahedral capsid containing 252 capsomeres and a linear genome anchored to a protein at each end. This virus is classified within species C and typically infects the respiratory epithelium of infants and young children, causing self‑limited fever, sore throat and conjunctivitis. Like other adenoviruses it replicates in the nuclei of epithelial cells and can persist in tonsillar tissue.
Biology and pathogenesis
Adenoviruses possess a sturdy icosahedral capsid measuring about 70 to 90 nm with fibre proteins projecting from each vertex. Their double‑stranded DNA genome is associated with core proteins and replicates in the host cell nucleus, producing progeny virions and sometimes establishing latent infection. More than a hundred antigenically distinct adenoviruses have been identified, with types 1, 2, 5 and others grouped within species C. Human adenovirus 1 is transmitted in respiratory droplets or contact with contaminated surfaces. After reaching the upper respiratory tract it infects epithelial cells, causing lytic replication that leads to sore throat, low‑grade fever and occasionally conjunctival inflammation. In many individuals the virus persists in lymphoid tissue of the nasopharynx or tonsils and may be shed without symptoms. Host immunity involves neutralising antibodies and cytotoxic T cells which help clear infection.
Clinical features and notable facts
HAdV‑1 infection often presents as febrile pharyngitis accompanied by conjunctivitis, a syndrome sometimes referred to as pharyngoconjunctival fever. Children attending daycare and military recruits living in close quarters are frequently exposed, and outbreaks have been reported in communal settings. Unlike types 7 or 14, which are associated with severe pneumonia, HAdV‑1 disease is usually mild and self‑limited. The virus can also be detected in stool samples but is rarely implicated in gastroenteritis; enteric types 40 and 41 are the primary adenoviral causes of paediatric diarrhoea. Vaccines against types 4 and 7 are used to protect recruits; no specific vaccine exists for type 1. Human adenovirus 1 infection is common worldwide, and by early childhood most individuals have developed antibodies. Infections typically resolve without complications, but immunocompromised hosts may experience prolonged viral shedding. In summary, HAdV‑1 is a ubiquitous respiratory adenovirus that exemplifies the ability of adenoviruses to persist in lymphoid tissue and occasionally cause outbreaks in crowded settings. Related Terms: Human Adenovirus 2, Human Adenovirus 3, Respiratory infection, Adenoviridae