Adenoviruses

Double-stranded, linear DNA enclosed in a naked icosadeltahedral capsid. Highly resistant to gastrointestinal secretions, such as gastric acid and bile, and resistance to drying and mild chlorine treatments. Transmission occurs via aerosols, the fecal-oral route (via fingers or contaminated pool water, for example), and fomites, such as pool towels. Crowded areas, such as camps or military bases provide excellent environments for adenovirus transmission. Adenovirus can cause lytic and latent infections, and, in non-human animals, oncogenic infections. Capsid proteins are arranged in icosahedral formation around the viral genome. There are 12 vertices with viral attachment proteins projecting from them. Vertex comprises a penton base with hexon capsid proteins on each side. The penton base inhibits host cell processes, which induces tissue damage. Fiber protein projects from penton base; the viral attachment protein is part of the fiber. The fiber mediates attachment to the host cell; it is the target of neutralizing antibodies. Adenoviruses are endemic. Most infections are asymptomatic, asymptomatic carriers unknowingly spread the virus. Infections are most severe in immunosuppressed patients, including some children. Adenoviruses 1-7 are most common. Entry occurs via the respiratory tract or the conjunctiva. Active lytic infection of muco-epithelial cells can take different forms, depending on the adenovirus present. Follicular conjunctivitis, aka, pinkeye is characterized inflammation of the tissue overlying the eye and eyelids. Acute febrile pharyngitis can occur with or without conjunctivitis (called pharyngo-conjunctival fever); this is common in schoolchildren, but can also occur in adults. It is usually mild and self-limiting. Acute respiratory disease can include tracheo-bronchitis or pneumonia; outbreaks are associated with adenovirus types 4 and 7, which are spread in close quarters, such as military bases. Gastroenteritis occurs in some patients. Adenoviruses cause an estimated 15% of gastroenteritis cases that require hospitalization, especially in infants. Latent infection in lymphoid cells occurs following active infection immunocompetent individuals. Immunosuppressed individuals, viremia and systemic infections can occur. This includes patients with congenital immunodeficiencies and transplant recipients. Systemic infection can lead to pneumonia, meningoencephalitis, or hepatitis. We can see nuclear inclusions that indicate the presence of adenovirus in liver cells of an individual who developed hepatitis.

• Hand-washing
• Chlorination of pools, which can reduce adenovirus transmission.
• New military recruits are vaccinated against adenoviruses types 4 and 7.
• There are no specific drugs to treat adenovirus infection; however, cidofovir and ribavirin are sometimes prescribed.

Images: “Adenovirus - Infectious Disease and Antimicrobial Agents.” Accessed July 3, 2018. http://www.antimicrobe.org/new/v01.asp. “Liver Tx Topic.” Accessed July 2, 2018. http://tpis.upmc.com/tpislibrary/HB/H00034f.html. “Adenovirus - Infectious Disease and Antimicrobial Agents.” Accessed July 3, 2018. http://www.antimicrobe.org/new/v01.asp.