At least 60 serotypes of adenovirus are currently described and these are members of 7 species classified A–G. About half of these subgroups produce a variety of clinical syndromes. Adenoviruses show a worldwide distribution and occur throughout the year. These infections are usually self-limited or clinically inapparent and occur most commonly among infants, young children, and military recruits. However, these infections may cause significant morbidity and mortality in immunocompromised persons, such as HIV-infected persons and COPD patients, as well as in patients who have undergone solid organ and hematopoietic stem cell transplantation or cardiac surgery or in those who have received cancer chemotherapy. A few cases of donor-transmitted adenoviral infection have been reported in past years. An outbreak with adenovirus type 55 was reported in 2017 from a neurosurgical unit in China.
Adenoviruses, although a common cause of human disease, also receive particular recognition through their role as vectors in gene therapy and vaccine development.
The incubation period is 4–9 days. Clinical syndromes of adenovirus infection, often overlapping, include the following. The common cold (see Chapter 8-10) is characterized by rhinitis, pharyngitis, and mild malaise without fever. Conjunctivitis is often present. Nonstreptococcal exudative pharyngitis is characterized by fever lasting 2–12 days and accompanied by malaise and myalgia. Lower respiratory tract infection may occur, including bronchiolitis, suggested by cough and rales, or pneumonia. Types 1, 2, 3, 4, and 7 commonly cause acute respiratory disease and atypical pneumonia; coinfections or serial infections are documented to occur. Infections are especially severe in Native American children. Adenovirus type 14 is increasingly reported as a cause of severe and sometimes fatal pneumonia in those with chronic lung disease but is also seen in healthy young adults and military recruit outbreaks. Viral or bacterial coinfections occur with adenovirus in 15–20% of cases. Pharyngoconjunctival fever is manifested by fever and malaise, conjunctivitis (often unilateral), mild pharyngitis, and cervical adenitis. Epidemic keratoconjunctivitis (transmissible person-to-person, most often types 8, 19, and 37) occurs in adults and is manifested by bilateral conjunctival redness, pain, tearing, and an enlarged preauricular lymph node (multiple types may be involved in a single outbreak). Type 53 (a D adenovirus) was the cause of a 2017 outbreak in a Los Angeles County Eye Clinic. Keratitis may lead to subepithelial opacities (especially with the above types). Acute hemorrhagic cystitis is a disorder of children often associated with adenovirus type 11 and 21.
Sexually transmitted genitourinary ulcers and urethritis may be caused by types 2, 8, and 37. Adenoviruses also cause acute gastroenteritis (types 40 and 41), mesenteric adenitis, acute appendicitis, rhabdomyolysis, and intussusception. Rarely, they are associated with encephalitis, meningitis, acute respiratory distress syndrome (ARDS), acute flaccid paralysis, and pericarditis. Adenovirus is commonly identified in endomyocardial tissue of patients with myocarditis and dilated cardiomyopathy. Risk factors associated with severity ...