Human adenovirus 55 (HAdV‑55) is an emergent recombinant genotype of species B adenoviruses. It is a non‑enveloped virus with an icosahedral capsid about 70‑90 nm and a linear double‑stranded DNA genome. Genetic analyses show that HAdV‑55 arose from recombination between adenovirus types 14 and 11. This virus primarily targets the respiratory tract and has caused severe pneumonia in otherwise healthy individuals.
Biology and pathogenesis
Like other adenoviruses, HAdV‑55 enters the body through inhalation of respiratory droplets or contact with contaminated surfaces. It binds to cellular receptors in the respiratory epithelium and replicates in the nucleus, leading to lytic destruction of infected cells. The recombinant genome confers properties from both parental types: the fibre and penton base genes resemble those of HAdV‑14, while the hexon gene is similar to HAdV‑11. This combination may contribute to its enhanced virulence. Host defence depends on neutralising antibodies and T cell responses, but many people lack immunity to this novel type.
Clinical features and outbreaks
HAdV‑55 infections typically present with high fever, cough, dyspnoea and radiographic evidence of pneumonia. Many patients progress to acute respiratory distress syndrome requiring intensive care. Outbreaks have been reported among military trainees and in community settings across Asia and Europe. Large clusters in China during 2011–2014 resulted in hundreds of cases of severe pneumonia with significant mortality. Because the virus is novel, there is no licensed vaccine; infection control measures and early recognition are vital to limit transmission. Supportive respiratory care is the mainstay of treatment, and antiviral agents such as cidofovir may be considered for severe disease.
Human adenovirus 55 illustrates the ability of adenoviruses to evolve through recombination and cause severe respiratory illness. Continued surveillance, rapid diagnostics and strict infection control are essential to mitigate its impact.
Related Terms: Human Adenovirus 14, Human Adenovirus 11, Human Adenovirus 7, Human Adenovirus 21