Human Adenovirus 4 is a species E adenovirus within the genus *Mastadenovirus*. This non‑enveloped icosahedral virus has a linear double‑stranded DNA genome and is a well‑known cause of acute respiratory disease, especially in congregate settings like military training camps.
Structure and Pathogenesis
Type 4 adenovirus particles are approximately 90 nanometres in diameter and consist of a proteinaceous icosahedral capsid surrounding the viral genome. The capsid is composed of hexon and penton base proteins with projecting fiber proteins that mediate attachment to host cell receptors such as coxsackie‑adenovirus receptor (CAR) and alpha v integrins. Following receptor‑mediated endocytosis, virions uncoat and deliver their DNA into the nucleus. Early gene expression triggers host shutoff, immune evasion and replication of the viral genome using a virus‑encoded DNA polymerase. Late gene products include structural proteins that assemble into new virions. Cell lysis releases progeny virus, allowing spread via aerosols and fomites.
Clinical Impact and Prevention
Adenovirus 4 is historically associated with outbreaks of acute respiratory disease among military recruits, causing fever, sore throat, cough and pneumonia. The virus can also circulate in civilian populations, leading to pharyngitis, conjunctivitis or bronchitis, but outbreaks are less common. Transmission occurs through respiratory droplets and contaminated surfaces. Most infections are self‑limited, though severe disease can occur in immunocompromised hosts. A live oral vaccine targeting adenovirus types 4 and 7 has been administered to U.S. military personnel to prevent training‑associated outbreaks. Laboratory diagnosis relies on PCR or viral culture, and management is supportive; cidofovir may be used in severe cases. Human adenovirus 4 underscores the importance of specific adenovirus types in closed communities and the value of targeted vaccination in high‑risk groups. Understanding its transmission and disease manifestations aids in prevention and control measures. Related Terms: human adenovirus 7, acute respiratory disease, adenovirus vaccine, species E, respiratory infections