Human Adenovirus 3 is a member of species B within the genus *Mastadenovirus*. It is a non‑enveloped icosahedral virus with a linear double‑stranded DNA genome. Type 3 adenoviruses are common causes of respiratory tract infections and pharyngoconjunctival fever, particularly in children.
Structure and Replication
Adenovirus 3 virions have an icosahedral capsid built from hexon and penton proteins. Fiber knobs protruding from each penton base attach to cellular receptors such as desmoglein 2 and CD46. After entry via receptor‑mediated endocytosis, the capsid uncoats, and the viral core is transported to the nucleus. Early genes encode proteins that promote viral DNA replication, inhibit apoptosis, and modulate host immune responses. DNA replication uses a viral DNA polymerase and terminal protein primer. Late genes code for structural proteins that assemble with replicated genomes to form new virions. New particles are released when infected cells lyse, allowing spread to adjacent epithelial tissues and through aerosols or contaminated water.
Clinical Features and Epidemiology
Type 3 adenoviruses are associated with upper respiratory infections and outbreaks of pharyngoconjunctival fever—an illness characterized by fever, sore throat, pharyngitis, and conjunctivitis. Transmission occurs by droplets, contaminated swimming pools, or fomites. In children and young adults, adenovirus 3 can cause bronchitis, pneumonia, or conjunctivitis. Immunocompromised patients may develop severe or disseminated disease. Species B adenoviruses, including types 3, 7, 14 and 21, have caused military and institutional outbreaks of acute respiratory disease. Diagnosis relies on PCR or viral culture, and supportive care is the primary therapy; cidofovir may be considered in severe immunocompromised cases. Adenovirus 3 has also been engineered as a vector for gene delivery because of its ability to infect dividing and non‑dividing cells, although adenovirus 5 is more commonly used. Human adenovirus 3 illustrates how specific adenovirus types can cause characteristic clinical syndromes and outbreaks. Awareness of its transmission routes and symptoms helps guide prevention and management, particularly in crowded settings and among vulnerable patients. Related Terms: human adenovirus 1, human adenovirus 7, pharyngoconjunctival fever, viral conjunctivitis, acute respiratory disease