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 tract infections (LRTI) each year in the U.S.
- Between 50-90% of LRTIs in children are caused by viruses
- Viruses are the fourth leading cause of hospital-treated pneumonia in otherwise healthy adults
Age – bimodal peaks
- Children <10 years
- Adults >55 years

Organisms

Although a wide variety of viral agents are capable of causing LRTI in adults and children, respiratory syncytial virus (RSV), adenovirus, influenza A and B, and parainfluenza 1, 2, and 3 cause 80-90% of LRTIs
- RSV and influenza are viruses associated with significant annual morbidity and mortality, and which have available therapies
  - RSV causes 50-90% of bronchiolitis infections and 5-40% of pneumonitis infections in children
  - Influenza can cause significant disease in adults and children

Risk Factors

Age – <2 years or >55 years
Compromised immune system
Preexisting chronic medical condition (cardiac, pulmonary, hepatic)

Clinical Presentation

Clinical presentation often does not distinguish viruses
- Nonspecific symptoms of cough, fever, sore throat, rhinorrhea, hoarseness, bronchitis, croup and bronchiolitis
Complications
- Infants, the elderly, and individuals with compromised cardiac, pulmonary or immune systems are at greatest risk for serious complications from LRTI
  - Severe viral pneumonia
  - Acute respiratory failure
  - Secondary bacterial pneumonia

Additional Information

Indications for Laboratory Testing

Tests generally appear in the order most useful for common clinical situations
Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Recommended Use	Limitations
CBC with Platelet Count & Automated Differential 0040003 Method: Automated Cell Count with Flow Cell Differential	Predominance of monocytes and lymphocytes may be diagnostic; white blood cell count is usually not elevated
Respiratory Viruses DFA with Reflex to Viral Culture 0060281 Method: Direct Fluorescent Antibody Stain	Panel includes influenza A and B, parainfluenza (1,2,3), RSV, adenovirus, human metapneumovirus If DFA is negative or inadequate, a viral culture will be added.	The adequacy of the direct specimen significantly influences the sensitivity of the DFA Inadequate specimen collection and too few cells on the slide may lead to failure of direct smears to detect respiratory viruses Other viruses such as HSV or CMV will not be routinely detected in this culture; decreased sensitivity for adenovirus using rapid culture
Respiratory Viruses DFA with Reflex to Respiratory Virus Mini Panel by RT-PCR 2002565 Method: Direct Fluorescent Antibody Stain	Screen for respiratory viruses by DFA with RT-PCR backup with DFA is inadequate or negative for influenza
Respiratory Mini Panel with H1N1 (2009) Typing by RT-PCR 2002559 Method: Reverse Transcription Polymerase Chain Reaction	Detect and type novel H1N1 virus	This test is authorized by FDA under Emergency Use Authorization Authorized only for detection of 2009 H1N1 influenza virus and not for any other viruses or pathogens Test is authorized for duration of declaration of emergency under section 564(b)(1) of the ACT, 21 U.S.C. §360bbb-3(b)(1) Declaration of emergency will expire April 16, 2010, unless terminated or revoked sooner or renewed

Additional Tests Available

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Respiratory Viruses Rapid Culture 2001504 Method: Cell Culture/Immunofluorescence	Respiratory viruses that can be isolated include influenza A & B, RSV, adenovirus, and parainfluenza 1, 2 & 3
Respiratory Viruses DFA 0060289 Method: Direct Fluorescent Antibody Stain	Rapid test for detecting adenovirus, influenza A & B, RSV and parainfluenza 1, 2 & 3 viruses Significantly more rapid and less expensive than PCR
Respiratory Virus Mini Panel by RT-PCR 0060764 Method: Reverse Transcription Polymerase Chain Reaction	Detects and identifies influenza A and B and RSV RT-PCR is a rapid and highly sensitive test for viruses; RT-PCR is also the most expensive test
Viral Culture 0065008 Method: Cell Culture
Respiratory Culture (Includes Gram Stain 0060101) 0060122 Method: Standard reference procedures for bacterial stain, aerobic culture, and identification. Sinus swabs or aspirates should be ordered as a Wound Culture (0060132).

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).