Nonenveloped (Naked) DNA Viruses
• Midsized viruses with a linear double-stranded DNA genome and naked, icosadeltahedral capsid that has fibers extending from the vertices.
1. Fibers extending from viral capsid bind to specific receptors on epithelial and other cells.
2. Primary lytic infection with accompanying inflammation occurs in mucous membranes of the respiratory tract, gastrointestinal tract, conjunctiva, and cornea.
3. Persistent, latent infection in lymphoid tissues (e.g., tonsils, adenoids, and Peyer patches) is common.
B Adenoviral illnesses (Table 21-1)
TABLE 21-1
Common Illnesses Associated with Adenoviruses
| Type of illness | Clinical features |
| Acute febrile pharyngitis | Fever, sore throat, cough, coryza, and other symptoms that may mimic streptococcal infection |
| Most common in young children (<3 yr) | |
| Acute respiratory disease | Rapid onset of fever, cough, sore throat, rhinorrhea, and cervical adenitis |
| Occurs mostly in military recruits | |
| Pharyngoconjunctival fever | Similar to acute pharyngitis but accompanied by conjunctivitis (“pink eye”) |
| Occurs in older children, often in outbreaks associated with use of poorly chlorinated swimming pools | |
| Preauricular lymphadenopathy important diagnostic finding | |
| Atypical pneumonia | Nonproductive cough with pulmonary infiltrates and effusions |
| Seen in children and adults | |
| Epidemic keratoconjunctivitis | Inflamed pebbled conjunctiva (pink eye) in adults similar to conjunctivitis in children but of longer duration and followed by keratitis |
| Usually associated with irritation to eye by dust or other debris | |
| Gastroenteritis | Diarrhea with possible vomiting primarily in infants and young children due to serotypes 40-42 |
| Other serotypes (e.g., 25-28) cause diarrhea in hospitalized patients. | |
| Acute appendicitis | Lymphoid hyperplasia in appendix compromises blood supply leading to acute inflammation. |
1. Incubation period for acute adenoviral illness is 4 to 9 days, but virions may be released for long periods, even after resolution of symptoms.
2. Acute, self-limited illness is the most common manifestation of adenoviral infection.
3. Infections occur primarily in children, military recruits, and immunocompromised individuals.
1. Dense, basophilic intranuclear inclusion body within infected cells is diagnostic of adenoviruses.
2. Adenovirus serotypes can be distinguished by immunoassay, DNA probe, or polymerase chain reaction (PCR) analysis of cultured specimens.
1. As naked capsid viruses, adenoviruses are resistant to drying and detergents and are very contagious.
2. Virions are spread via aerosols, fecal-oral route, fomites, and close contact and in inadequately chlorinated swimming pools.
