Respiratory Viruses

Clinical Background

Viral respiratory tract infections are the most common diseases affecting humans throughout the world.

Epidemiology

Incidence
- More than 5 million children under the age of 6 experience lower respiratory infections (LRI) each year in the U.S.
- Between 50-90% of LRI in children are caused by viruses
- Viruses are the fourth leading cause of hospital-treated pneumonia in otherwise healthy adults
Age
- Peak incidence in childhood years
- Second peak in >55 year olds

Organisms

Although a wide variety of viral agents are capable of causing lower respiratory infections (LRI) in adults and children, RSV, influenza A and B, parainfluenza 1, 2, and 3 and adenovirus cause 80-90% of LRI
- Of particular importance are RSV and influenza, agents that are associated with significant morbidity and mortality and for which therapies are available

Risk Factors

Age - (<2 years of age or >55 years of age )
Immunocompromised
Preexisting chronic medical condition

Clinical presentation

Infants, the elderly, and individuals with compromised cardiac, pulmonary or immune systems are at greatest risk for serious complications from these viruses
Nonspecific symptoms of cough, fever, sore throat, rhinorrhea, hoarseness, bronchitis, croup, and bronchiolitis
Clinical presentation often does not distinguish viruses

See Also

Adenovirus

Enterovirus - EV

Influenza

Parainfluenza Virus 1, 2, 3

Respiratory Syncytial Virus - RSV

Tests

Tests generally appear in the order most useful for common clinical situations

Test name: Respiratory Virus Mini Panel by RT-PCR

ARUP #: 0060764

Methodology: Reverse Transcription Polymerase Chain Reaction

Use:

Identify respiratory virus responsible for disease; includes testing for influenza A & B and respiratory syncytial virus (RSV)

PCR is a rapid and highly sensitive test for viruses

PCR is also the most expensive test

Limitations:

A negative result does not rule out the presence of PCR inhibitors in the patient specimen or respiratory viral DNA concentrations below the level of detection by the assay

Test name: Viral Culture

ARUP #: 0065008

Methodology: Cell Culture

Use:

Order if DFA test result is negative

Considered the gold standard for identifying viral agent responsible for infection

Limitations:

Viral culture requires about 24-72 hours with most agents

Test name: Respiratory Viruses DFA

ARUP #: 0060289

Methodology: Direct Fluorescent Antibody Stain

Use:

Rapid test for detecting adenovirus, influenza A and B, respiratory syncytial virus and parainfluenza 1, 2 and 3 viruses

Significantly more rapid and less expensive than PCR

Limitations:

The adequacy of the direct specimen significantly influences the sensitivity of the DFA

Naso-pharyngeal aspirate or other respiratory secretion must contain intact respiratory epithelium to be deemed adequate for examination

Inadequate specimen collection and too few cells on the slide may lead to failure of direct smears to detect respiratory viruses Excess mucus or lumpy smears can cause:

False-positives by nonspecifically trapping the antibody reagent
False-negatives by clumping the cells, thereby masking the virus antigens

Follow-up:

Viral Culture of DFA-negative specimens is strongly recommended

Refer to Respiratory Viruses DFA with Reflex to Viral Culture

Additional Tests Available

Test name: Respiratory Viruses DFA with Reflex to Viral Culture

ARUP #: 0060281

Methodology: Direct Fluorescent Antibody Stain

Comments:

Test name: Respiratory Culture (Includes Gram Stain 0060101)

ARUP #: 0060122

Methodology: Standard reference procedures for bacterial stain, aerobic culture, and identification. Sinus swabs or aspirates should be ordered as a Wound Culture (0060132).

Comments:

Additional Information

In general, the sensitivity of DFA testing for influenza, parainfluenza and respiratory adenovirus improves with specimen type (eg, true sputum and nasopharyngeal are better than throat swabs).

References

General References

Brice GT, Drews SJ, Low DE. Respiratory virus panels for global surveillance of emerging infectious diseases. J Clin Virol. 2007;40 Suppl 1:S58-S60.

Carman WF, Mahony JB. The pathogens. J Clin Virol. 2007;40 Suppl 1:S5-S10.

Crowe JE Jr, Williams JV. Immunology of viral respiratory tract infection in infancy. Paediatr Respir Rev. 2003;4(2):112-119.

Ginocchio CC. Detection of respiratory viruses using non-molecular based methods. J Clin Virol. 2007;40 Suppl 1:S11-S14.

Henrickson KJ. Cost-effective use of rapid diagnostic techniques in the treatment and prevention of viral respiratory infections. Pediatr Ann. 2005;34(1):24-31.

Ieven M. Currently used nucleic acid amplification tests for the detection of viruses and atypicals in acute respiratory infections. J Clin Virol. 2007;40(4):259-276.

Mahony JB. The clinical need for the RVP test. J Clin Virol. 2007;40 Suppl 1:S36-S38.

Mazzulli T. Value of RVP in clinical settings: intensive care. J Clin Virol. 2007;40 Suppl 1:S55-S57.

Mizgerd JP. Acute lower respiratory tract infection. N Engl J Med. 2008;358(7):716-727.

Monto AS. Occurrence of respiratory virus: time, place and person. Pediatr Infect Dis J. 2004;23(1 Suppl):S58-S64.

Templeton KE. Why diagnose respiratory viral infection?. J Clin Virol. 2007;40 Suppl 1:S2-S4.

References from the ARUP Institute for Clinical and Experimental Pathology Research®

Petti CA, Hillyard D. Value of RVP in clinical settings: older adults. J Clin Virol. 2007;40 Suppl 1:S53-S54.

Taggart EW, Hill HR, Martins TB, Litwin CM. Comparison of complement fixation with two enzyme-linked immunosorbent assays for the detection of antibodies to respiratory viral antigens. Am J Clin Pathol. 2006;125(3):460-466.

Medical Reviewers

Carney, Heather, M.D. Assistant Medical Director, Transfusion Services at ARUP Laboratories; Pathology, University of Utah

Hillyard, David R., M.D. Medical Director, Molecular Infectious Diseases at ARUP Laboratories; Associate Professor, Pathology, University of Utah

Petti, Cathy A., M.D. Medical Director, Infectious Diseases at ARUP Laboratories; Assistant Professor, Pathology and Medicine, University of Utah

She, Rosemary C., M.D. Assistant Medical Director, Infectious Diseases at ARUP; Clinical Assistant Professor, Clinical Pathology, University of Utah

Comprehensive Review: September 2008
Last Update: September 2008