Human adenovirus 3 is a non‑enveloped double‑stranded DNA virus and one of the many antigenically distinct members of the Adenoviridae family. Its icosahedral capsid measures about 70 to 90 nm and encloses a linear DNA genome associated with core proteins. This type belongs to species B and is a frequent cause of acute respiratory disease, particularly in young children and in institutional outbreaks.
Biology and pathogenesis
Adenoviruses replicate in the host cell nucleus, producing progeny virions or establishing latent infection depending on the cell type. More than a hundred human adenovirus types exist; type 3 is grouped within species B, which often shows tropism for the respiratory tract. Transmission occurs via droplets, contaminated surfaces or close contact. After infecting epithelial cells of the nasopharynx and conjunctiva, the virus undergoes lytic replication leading to cell destruction and inflammation. Persistence in lymphoid tissue can result in asymptomatic shedding. Host immunity includes neutralising antibodies and cytotoxic T‑cell responses that clear infection, but reinfection with heterologous adenovirus types can occur.
Clinical features and notable facts
HAdV‑3 is well known for causing outbreaks of pharyngitis, fever and conjunctivitis in schools, childcare centres and military camps. Along with types 7 and 21, it has been implicated in severe respiratory disease with significant mortality and morbidity among young children and immunocompromised patients. Patients may present with high fever, sore throat, cough and cervical adenopathy; pneumonia can develop, particularly in infants. Pharyngoconjunctival fever results when infection involves both the upper respiratory tract and the conjunctiva, sometimes linked to swimming pool exposure. Unlike types that primarily cause keratoconjunctivitis (8, 19, 37) or gastroenteritis (40/41), HAdV‑3 is predominantly a respiratory pathogen. Although most infections are self‑limiting, the propensity of HAdV‑3 to cause clusters of respiratory illness warrants attention in communal settings. Preventive measures include good hand hygiene, avoidance of crowded swimming pools and, for high‑risk populations, surveillance during outbreaks. There is no specific antiviral therapy for adenovirus infection, so management is supportive. Related Terms: Human Adenovirus 7, Human Adenovirus 21, Acute respiratory disease, Pharyngoconjunctival fever