Case 5

1. Describe the modes of adenoviral transmission. 


Adenoviruses causing respiratory tract infection usually are transmitted by respiratory tract secretions through person-to-person contact, fomites, and aerosols. Because adenoviruses are stable in the environment, fomites may be important in their transmission. The conjunctiva can provide a portal of entry. Community outbreaks of adenovirus-associated pharngonconjunctival fever have been attributed to exposure to water from contaminated swimming pools and fomites, such as shared towels. Epidemic keratoconjunctivitis often has been associated with nosocomial transmission in ophthalmologists’ offices. Enteric strains of adenoviruses are transmitted by the fecal-oral route. Nosocomial spread often has resulted from exposure to contaminated hands of health care workers and infected equipment, including pneumotonometers and opthalmologic solutions.

 

 

 

 

 

 

 

2. Describe the clinical manifestations of adenoviral infections.  


The most common site of adenovirus infection is the upper respiratory tract. Manifestations include symptoms of the common cold, pharyngitis, pharyngoconjunctival fever, tonsillitis, otitis media, keratoconjunctivitis, often associated with fever. Life-threatening disseminated infection, severe pneumonia, meningitis, and encephalitis occasionally occur, especially among young infants and immunocompromised hosts. Adenoviruses are infrequent causes of acute hemorrhagic conjunctivitis, a pertussis-like syndrome, croup, bronchiolitis, hemorrhagic cystitis, and genitourinary tract disease.

In children, the best described syndrome attributed to adenoviruses is the so-called pharyngoconjunctival fever. This disease occurs in small outbreaks and seen by physicians at children’s summer camps. It is characterized by conjunctivitis, pharyngitis, rhinitis, cervical adenitis, and temperatures to 380C. The onset is acute, and the fever and other symptoms last 3-5 days. Bulbar and palpebral conjunctivitis may be the only finding, and the palpebral conjunctivae usually have a granular appearance.

A few adenovirus serotypes, types 40 and 41, have been associated with gastroenteritis, and are responsible for about 4% of serious diarrhea in infants and children.

The predominant cause of exudative tonsillitis in infants and toddlers is of adenoviral etiology.

 

 

 

 

 

 

 

3. What is known about the pathogenesis of adenoviral infections? 


The oropharyngeal and nasopharyngeal mucous membranes are the tissues primarily affected early in acute infection.

Adenoviruses appear to be capable of at least three types of interaction with cells.

1) The first is a lytic infection in which the virus goes through an entire replicative cycle. Lytic infection occurs in human epithelial cells and results in cell death and in the production of 10,000 – 1 million progeny viruses per cell, of which 1-5 percent are infectious.

2) The second interaction is a latent or chronic infection. This usually involves lymphoid cells. During latent infection, only small numbers of viruses may be released, and cell death may be outstripped by cell multiplication, thereby resulting in inapparent infection. The mechanisms are not clearly established.

3) The third significant virus – cell interaction occurring with adenoviruses is that of oncogenic transformation. In this situation, only the early steps in virus replication occur. The viral DNA is apparently integrated into and replicated with the cell’s DNA, but no infectious virions are produced. In all three types of infection, virus-specific proteins (T antigens) are synthesized. These antigens give evidence of adenoviral presence even in the absence of infectious virus. The T antigens are detected either by complement fixation or by immunofluorescence assays using serum from hamsters bearing tumors induced by adenovirus.

 

 

 

 

 

 

 

4. What type of isolation should the patient be in while in the hospital? 


For young children with respiratory tract infection, contact and droplets precautions are indicated for the duration of hospitalization. For patients with conjunctivitis, contact precautions in addition to standard precautions are recommended. For diapered and incontinent children with adenoviral gatroenteritis, contact precautions in addition to standard precautions are indicated for the duration of the illness.

 

 

 

 

 

 

 

5. How is the viral infection detected? 


Detection of adenovirus infection by culture or antigen is the preferred diagnostic method.

Adenoviruses associated with respiratory tract disease can be isolated from pharyngeal secretions, eye swabs, and feces by inoculation of specimens into a variety of cell cultures. A pharyngeal isolate is more suggestive of recent infection than is a fecal isolate, which may indicate either prolonged carriage or recent infection.

Adenovirus antigens can be detected in body fluids of infected persons by immunoassay techniques, which are especially useful for diagnosis of diarrheal disease, because enteric adenovirus types 40 and 41 usually cannot be isolated in standard cell cultures. Enteric adenoviruses also can be identified by electron microscopy of stool specimens. Multiple methods to detect group-reactive hexon antigens in body secretions and tissue have been developed. Also, detection of viral DNA can be accomplished with genomic probes, synthetic oligonucleotide probes, or gene amplification by polymerase chain reaction. Serodiagnosis is based on detecting a 4-fold or greater rise in antibodies to a common adenovirus antigen (eg, hexon). Serodiagnosis is used primarily for epidemiologic studies.

 

 

 

 

 

 

 

 

6. Describe the measures for prevention of the spread of adenoviral infection.

Adequate chlorination of swimming pools is recommended to prevent pharyngoconjunctival fever. Epidemic keratoconjunctivitis associated with ophthalmologic practice can be difficult to control and requires use of single-dose medication dispensing and strict attention to hand washing and instrument sterilization procedures. Effective disinfection can be accomplished by immersion of contaminated equiment in a 1% solution of sodium hypochlorite for 10 minutes or by steam autoclaving.

Health care personnel with known or suspected adenoviral conjunctivitis should avoid direct patient contact for 14 days after the onset of disease in their second eye. Because adenoviruses are particularly difficult to eliminate from skin, fomites, and environmental surfaces, assiduous adherence to hand washing and use of disposable gloves when caring for infected patients are recommended.

Children who participate in group child care, particularly children from 6 months through 2 years of age, are at increased risk of adenoviral respiratory tract infections and gastroenteritis. Measures for preventing spread of adenovirus infection in this setting have not been determined, but frequent hand-washing is recommended.