Parainfluenza virus, Types 1, 2, 3
Diagnosing parainfluenza viral infections
Parainfluenza virus types 1, -2 and -3 can infect and cause disease throughout the upper and lower respiratory tract. Most Parainfluenza virus infections manifest clinically as acute laryngotracheobronchitis (croup) in infants and children, as well as tracheobronchitis, bronchitis, pneumonia and a range of symptoms associated with the upper respiratory tract. Occasionally parainfluenza virus infections can be severe in infants, causing obstruction of airways and respiratory distress which may lead to increased morbidity and mortality in patients with underlying disease such as cystic fibrosis or in immunocompromised patients.
Parainfluenza viruses are spread by direct contact or inhalation of virus-containing droplets shed from the respiratory tract of symptomatic individuals. Nasal secretions can contain high concentrations of virus. The virus multiplies in the ciliated columnar epithelial cells of the upper and lower respiratory tract causing cell necrosis and sloughing. Viral shedding occurs from 1 day before, up to 7 days after the onset of symptoms. Shedding may persist in immunocompromised patients. Parainfluenza viruses have been associated with outbreaks of respiratory tract infections in pediatric wards and geriatric wards resulting in prolonged hospitalization and increased morbidity and mortality. Rapid diagnosis is important in the management of patients and the control of outbreaks.
Parainfluenza viruses are members of the genus Paramyxovirus classified within the family Paramyxoviridae. There are 6 species of Paramyxovirus known to infect man with include Parainfluenza viruses 1, 2, 3 and 4 (subtypes 4a and 4b), Mumps virus and Newcastle Disease virus. Of the 4 Parainfluenza viruses, types 1, 2 and 3 are now recognized as a major cause of acute respiratory disease in infants and children.
A positive result indicates that virus was present in the specimen submitted. Clinical correlation is necessary to determine the significance of this finding as asymptomatic, persistent, or recurrent adenovirus infections can occur.
Negative results may be seen in a number of situations including absence of viral disease, nonviable organisms submitted or suboptimal specimen collection/transport.
Leland, D. S. 2007. Parainfluenza and Mumps Viruses, p. 1352-1360. In Murray, P. R., Baron, E. J., Jorgensen, J. H., Landry, M. L., and Pfaller, M. A. Manual of Clinical Microbiology, 9th ed., vol. 2. ASM Press, American Society for Microbiology, Washington, DC.
Wright, P. F. 2010. Parainfluenza Viruses, p. 2195-2199. In Mandell, D., Bennett, J. E., and Dolin, R. Principles and practice of infectious diseases, 7th ed., vol. 2. Churchill Livingstone, Elsevier, Philadelphia, PA.