Adenoviruses are DNA viruses classified according to 3 major capsid antigens (hexon, penton, and fiber). There are 7 human adenovirus species (A to G) and 57 serotypes. Different serotypes are associated with different conditions.
Adenoviruses are commonly acquired by contact with respiratory secretions (including those on fingers of infected people) from an infected person or by contact with a contaminated object (eg, towel, instrument). Infection may be airborne or waterborne (eg, acquired while swimming in lakes or in swimming pools without adequate chlorine). Asymptomatic respiratory or gastrointestinal viral shedding may continue for months, or even years.
Symptoms and Signs of Adenovirus Infections
In immunocompetent hosts, most adenovirus infections are asymptomatic. When infections are symptomatic, a broad spectrum of clinical manifestations is possible because most adenoviruses that cause mild disease have affinity for a variety of tissues.
Most symptomatic infections occur in children and cause fever and upper respiratory symptoms, including pharyngitis, otitis media, cough, and exudative tonsillitis with cervical adenopathy that can be difficult to distinguish from group A streptococcal pharyngitis Streptococcal pharyngitis Streptococci are gram-positive aerobic organisms that cause many disorders, including pharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. Symptoms vary with the organ... read more . Adenovirus types 3 and 7 cause a distinct syndrome of conjunctivitis, pharyngitis, and fever (pharyngoconjunctival fever).
Rare adenoviral syndromes in infants include severe bronchiolitis Bronchiolitis Bronchiolitis is an acute viral infection of the lower respiratory tract affecting infants 24 months and is characterized by respiratory distress, wheezing, and/or crackles. Diagnosis is suspected... read more and pneumonia Overview of Pneumonia Pneumonia is acute inflammation of the lungs caused by infection. Initial diagnosis is usually based on chest x-ray and clinical findings. Causes, symptoms, treatment, preventive measures, and... read more . In closed populations of young adults (eg, military recruits), outbreaks of respiratory illness may occur; symptoms include fever and lower respiratory tract symptoms, usually tracheobronchitis but occasionally pneumonia.
Case clusters of severe respiratory disease, caused by specific adenoviruses (particularly types 7, 14, and 55), have occurred in healthy adults.
Adenoviral infections are being increasingly recognized as causes of severe respiratory and other clinical disease in immunocompromised adults.
Epidemic keratoconjunctivitis Etiology is sometimes severe and occurs sporadically and in epidemics. Conjunctivitis is frequently bilateral. Preauricular adenopathy may develop. Chemosis, pain, and punctate corneal lesions that are visible with fluorescein staining may be present. Systemic symptoms and signs are mild or absent. Epidemic keratoconjunctivitis usually resolves within 3 to 4 weeks, although corneal lesions may persist much longer.
Nonrespiratory adenoviral syndromes include hemorrhagic cystitis, diarrhea in infants, and meningoencephalitis.
Most patients recover fully. Even severe primary adenoviral pneumonia is not fatal except for rare fulminant cases, predominantly in infants, military recruits, and immunocompromised patients.
Diagnosis of Adenovirus Infections
For severe disease, polymerase chain reaction (PCR) testing of respiratory secretions and blood
Laboratory diagnosis of adenovirus infection rarely affects management. During the acute illness, the virus can be isolated from respiratory and ocular secretions and frequently from stool and urine. A 4-fold rise in the serum antibody titer can indicate recent adenoviral infection but has little clinical utility.
PCR testing can detect adenovirus DNA in respiratory secretions and blood and is useful when patients have severe disease and a diagnosis is needed.
Treatment of Adenovirus Infections
Treatment of adenovirus infections is symptomatic and supportive. No antiviral agents are proven effective, although ribavirin and cidofovir have been used in immunocompromised patients with varying results.
Prevention of Adenovirus Infections
Vaccines containing live adenovirus types 4 and 7, given orally in an enteric-coated capsule, can prevent most illness caused by these two types. The vaccine was unavailable for a number of years but was reintroduced in 2011. However, it is available only for military personnel. It may be given to patients aged 17 through 50 years and should not be given to women who are pregnant or breastfeeding.
To minimize transmission, health care practitioners should change gloves and wash hands after examining infected patients, sterilize instruments adequately, and avoid using the same ophthalmologic instruments in multiple patients. Adenoviruses are resistant to many common disinfectants; bleach-based products containing 2000 to 5000 ppm chlorine are recommended, as are the US Environmental Protection Agency (EPA) recommended antimicrobial products effective against norovirus. The US Centers for Disease Control and Prevention (CDC) provides specific recommendations for disinfecting ophthalmologic equipment to prevent epidemic keratoconjunctivitis.
Adenoviruses can be spread through contact with secretions from an infected person or contact with a contaminated object.
Most infections are mild; manifestations (eg, fever, upper and lower respiratory symptoms, pharyngitis, conjunctivitis) vary widely depending on the serotype.
Severe illness occurs mainly in infants and immunocompromised patients but occasionally occurs in healthy adults.
Treatment is supportive.
An oral vaccine can reduce incidence of lower respiratory disease but is available only for military personnel.