What are the key points to cover in a lecture about adenovirus, including its types, transmission, clinical manifestations, diagnosis, treatment, and prevention strategies?

Adenovirus Lecture: Key Clinical Points

Viral Structure and Characteristics

Adenoviruses are double-stranded DNA viruses with specific tropism for respiratory epithelium, functioning in an extrachromosomal manner without integrating into the host genome. 1 This structural characteristic distinguishes them from retroviruses and has important implications for both natural infection and their use as gene therapy vectors. 1

• The virus demonstrates remarkable environmental stability, surviving on surfaces for up to 28 days in a desiccated state, making it extremely contagious. 2
• Adenovirus does not require host cell replication for gene transfer and expression, unlike retroviruses. 1

Transmission Mechanisms

Transmission occurs through three primary routes: respiratory droplets, direct contact with infected individuals or contaminated personal items, and fomite transmission from environmental surfaces. 2

• Direct contact transmission happens through sharing towels, pillows, bedding, and eating utensils. 2
• The extended surface survival period (up to 28 days) makes fomite transmission particularly concerning in healthcare and childcare settings. 2
• Patients remain infectious for 10-14 days from symptom onset, with active viral shedding throughout this period. 3, 2, 4

Clinical Manifestations by System

Respiratory Disease

Upper respiratory tract infection is the most common presentation, featuring fever, rhinorrhea, congestion, sore throat, sneezing, and cough. 1, 3

• Lower respiratory involvement manifests as bronchiolitis, pneumonia, or croup, particularly in children. 3
• Parainfluenza-like croup syndrome can occur with certain serotypes. 1
• Exacerbations of chronic obstructive pulmonary disease and asthma have been documented in adults. 1, 3

Ocular Disease

Follicular conjunctival reaction with subconjunctival hemorrhage, chemosis, and watery discharge characterizes adenoviral conjunctivitis. 3

• Epidemic keratoconjunctivitis presents with marked lid swelling, chemosis, epithelial sloughing, or membranous conjunctivitis in severe cases. 3
• Adenovirus contributes to 5-20% of acute conjunctivitis cases. 3
• Severe eye pain or vision changes indicate corneal involvement requiring immediate evaluation. 2

Gastrointestinal Disease

Adenovirus serotypes 40 and 41 cause gastroenteritis, contributing to 5-20% of hospitalizations for childhood diarrhea. 3

• Enteric adenoviruses may not be recovered in routine viral culture, requiring specialized detection methods. 1
• Signs of dehydration from persistent diarrhea require immediate medical attention. 2

Dermatologic Manifestations

Rash occurs in approximately one-third of children with adenovirus infection but is rare in adults. 3

• Rash patterns vary considerably: petechial, maculopapular, diffuse erythema, or other morphologies. 3
• The rash typically appears later in the disease course, with median onset of 5 days after symptom onset. 3
• Distribution is variable, potentially involving extremities, trunk, face, or rarely palms and soles. 3

Diagnostic Approach

Specimen Collection

Nasopharyngeal swabs or respiratory secretions in viral transport medium are optimal specimens for respiratory disease. 1, 3

• Conjunctival swabs are appropriate for ocular disease. 3
• Stool specimens require specialized cultures or molecular assays for enteric adenoviruses. 1
• All specimens should be transported at room temperature within 2 hours. 1

Testing Modalities

Rapid immunodiagnostic testing has 88-89% sensitivity and 91-94% specificity for adenovirus conjunctivitis and can prevent misdiagnosis. 3

• PCR testing provides highly sensitive and specific detection of adenovirus DNA when available. 3
• Viral conjunctivitis in the presence of upper respiratory infection can often be diagnosed clinically without additional testing. 3
• Culture may take 4-7 days for detection and is less commonly used now. 1

Treatment Strategies

Immunocompetent Patients

Supportive care remains the cornerstone of management, including hydration, antipyretics, and respiratory support as needed. 3, 4

• No specific antiviral therapy is indicated for self-limited gastroenteritis or upper respiratory infections. 4
• Monitor for clinical deterioration over 7-10 days, which is the typical illness duration. 3, 4

Immunocompromised or Severely Ill Patients

Cidofovir is the treatment of choice for life-threatening adenovirus infections in severely ill or immunocompromised children, despite the lack of randomized controlled trials. 4

• The dosing regimen is 5 mg/kg IV once weekly for 2 weeks, then once every other week. 4
• Mandatory monitoring of renal function is required due to considerable nephrotoxicity risk. 4

Prevention and Infection Control

Hand Hygiene

Hand hygiene with soap and water is essential, as alcohol-based sanitizers alone are insufficient against adenovirus. 2

Environmental Disinfection

Disinfecting surfaces daily using dilute bleach solution (1:10 household bleach to water ratio) is the only reliably effective disinfectant against adenovirus. 2, 4

Isolation Precautions

Isolate infected children in hospitals and daycare settings to prevent outbreaks, maintaining isolation for 10-14 days from symptom onset. 4

• Avoid close contact, particularly face-to-face interaction within 6 feet. 2
• Separate personal items including towels, pillows, bedding, and eating utensils. 2

Prognostic Factors

Poor outcomes are associated with specific adenovirus serotypes, particularly types 3 and 7. 4

• Age under 1 year with myocarditis shows 5-year survival of only 66% with adenovirus versus 95% without. 4
• Working in healthcare or childcare settings increases transmission risk to vulnerable populations. 2

Critical Pitfalls to Avoid

Underestimating contagiousness results in inadequate infection control, as the virus survives for weeks on surfaces. 3

• Do not rely solely on alcohol-based hand sanitizers; soap and water are required. 2
• Do not assume patients are no longer infectious after fever resolves; the infectious period extends 10-14 days from symptom onset. 3, 2, 4
• Do not overlook the need for specialized testing for enteric adenoviruses, as they may not be recovered in routine viral culture. 1