Human parainfluenza viruses (HPIVs) are among the most common causes of respiratory tract infection, especially in young children. HPIV is a member of the Paramyxoviridae family of viruses with 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 is a common virus infection that often resembles the common cold with mild symptoms such as a runny nose, coughing and low-grade fever; however, HPIV can cause more severe diseases such as bronchiolitis and pneumonia in young children. Those at greatest risk of severe infection include premature infants and children with heart or lung disease.
There are four types of HPIV (HPIV-1, HPIV-2, HPIV-3 and HPIV-4). Although all four types of HPIV 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 that causes a characteristic bark-like cough, infecting mostly infants and young children. HPIV infections can occur any time of year, but most infections occur from October through April.
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 two to seven days and pediatric patients generally recover in seven to ten days. Half of all infants become infected during their first year of life, while virtually all children have been infected by age six.
There is no vaccine for available for HPIV. Healthcare and childcare providers can help prevent the spread of HPIV by practicing good hygiene and keeping surfaces clean including:
Washing hands frequently
Wiping down surfaces with disinfectant
When possible, avoid close contact with an infected person.
Clinicians are not able to accurately diagnose HPIV infection based on symptoms alone. There are many viruses that cause respiratory infection and create similar symptoms.
Laboratories test for HPIV in several ways. Traditionally, viral culture was used to detect human parainfluenza virus. Improvements in virus culture techniques now allow for results within 48 to 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 and accurate methods to detect HPIV. The direct fluorescent antibody method allows detection of the virus within two to three hours but is labor intensive and requires considerable experience.
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.
References
Frost HM, Robinson CC, Dominquez SR. Epidemiology and clinical presentation of parainfluenza type 4 in children: a 3-year comparative study to parainfluenza types 1-3. J Infect Dis. 2014 Mar 1;209(5):695-702. https://academic.oup.com/jid/article/209/5/695/887957
Mahoney JB. Detection of Respiratory Viruses by Molecular Methods. Clin Microbiol Rev. 2008;21(4):716. https://journals.asm.org/doi/10.1128/CMR.00037-07
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