Parainfluenza Virus

Human parainfluenza viruses

Human parainfluenza viruses (HPIV) are among the most common causes of respiratory tract infection especially in young children. HPIV is a member of the Paramyxoviridae family of viruses. There are 4 types of HPIV (PIV 1-4).¹  HPIV has an RNA genome enclosed in a capsid surrounded by a lipid envelope. Much of the pathology caused by HPIV is related to damage of the lining of the small airways of the respiratory tract.

HPIV infection ^{2, 3}

HPIV is a very common virus infection that often resembles the common cold with mild symptoms such as a runny nose, coughing and low-grade fever. HPIV is responsible for many cases of bronchiolitis and pneumonia in young children. Those at greatest risk of severe infection include premature infants and children with heart or lung disease. Although all 4 types cause disease, most significant infections are caused by HPIV-1 and HPIV-3 whereas HPIV-4 is the least common cause of disease. HPIV-1 is the major cause of the syndrome referred to as “croup” which is laryngotracheitis in infants and young children.

Transmission

HPIV is readily spread from contact with respiratory secretions from infected individuals or contaminated surfaces and objects. The incubation period of HPIV infection ranges from 2-7 days and pediatric patients generally recover in 7-10 days.^{2, 3} Half of all infants become infected during their first year of life, while virtually all have been infected by the age of six.3 HPIV infections can occur any time of year, but most infections occur during fall through spring.^{2, 3}  

Medical Management of HPIV infection ^{2, 3}

Management of an HPIV infection is generally focused on symptomatic therapy. When an HPIV infection becomes more serious and progresses to bronchiolitis, patient management goals are to relieve respiratory distress, alleviate airway obstruction, and improve oxygen levels.

Diagnosis

Clinicians are not able to accurately diagnose HPIV infection based on signs and symptoms alone. There are many other viruses that infect the respiratory tract and there is a large overlap of symptoms among these infections. There are a number of methods available to laboratories to detect HPIV in respiratory specimens from patients.⁴ Traditionally, laboratories used viral culture to detect parainfluenza virus and improvements in virus culture technique susing immunofluorescence have reduced time to results to 48-72 hours. There are no rapid point-of-care tests available for HPIV. Molecular methods such as reverse transcription polymerase chain reaction (RT-PCR)-based tests are the most sensitive methods to detect HPIV. 

Prevention of HPIV infection

There is no vaccine for available for HPIV. Prevention of HPIV infection depends on the behavior of child care providers and health care providers to reduce the spread of HPIV by practicing good medical hygiene.

References

¹ Frost HM, Robinson CC, Dominquez SR.  Epidemiology and clinical presentation of parainfluenza type 4 in children: a 3-year comparative study toparainfluenza types 1-3. J. Infect. Disease. 2014 Mar 1; 209(5):695-702.

² http://www.cdc.gov/parainfluenza

³ http://emedicine.medscape.com/article/224708-overview

⁴ Mahoney, James B. Detection of Respiratory Viruses by Molecular Methods. Clin Microbiology Rev. 2008, 21(4): 716. DOI: 10: 1128/CMR 00037-17.