Human adenovirus 55 is an emergent recombinant species B adenovirus that causes severe acute respiratory disease. It is a non‑enveloped, double‑stranded DNA virus with an icosahedral capsid and results from recombination between adenovirus type 11 and type 14.
Structure and Genetic Origin
Human adenovirus 55 shares the typical adenovirus architecture: an icosahedral capsid formed by hexon and penton proteins surrounding a linear double‑stranded DNA genome. The virion has fibers projecting from each vertex that bind cellular receptors, initiating entry. Phylogenetic analyses show that its genome arose from homologous recombination between the hexon gene of adenovirus 11 and the backbone of adenovirus 14, giving it antigenic properties of type 11 while retaining the cell tropism and virulence of type 14. Like other adenoviruses it replicates in the nucleus, using early gene products to subvert host polymerases and late gene products to assemble progeny. The recombinant genome allows the virus to evade pre‑existing immunity in populations previously exposed to either parental strain.
Clinical Impact and Epidemiology
Adenovirus 55 primarily causes outbreaks of acute respiratory disease characterized by fever, cough, sore throat and, in severe cases, pneumonia. It has been implicated in clusters among military recruits, students and hospital settings, and has been reported in Asia, Europe and the Americas. Transmission occurs via respiratory droplets and contaminated surfaces, with incubation periods of 4–8 days. Cases can progress to severe pneumonia requiring hospitalization, especially in young adults and individuals with comorbid conditions. Diagnosis relies on polymerase chain reaction or viral culture. There is no specific antiviral therapy or vaccine; management is supportive, and infection control measures such as hand hygiene, respiratory etiquette and isolation of affected individuals are critical to limit spread. Surveillance is important because recombination events can lead to further evolution and unexpected outbreaks. Adenovirus 55 is an important reminder that genetic recombination can create novel pathogens with enhanced virulence and altered antigenicity. Continued monitoring and preventive measures are essential to mitigate its public health impact. Related Terms: adenovirus, acute respiratory disease, recombination, outbreak, pneumonia