eMedicine Specialties > Pediatrics: General Medicine > Infectious Disease

Parainfluenza Virus Infections

Roy M Vega, MD, Assistant Professor of Pediatrics, Albert Einstein College of Medicine; Director, Pediatric Emergency Services, Department of Emergency Medicine, Bronx Lebanon Hospital Center, Bronx, NY

Updated: Aug 28, 2009

Introduction

Background

Human parainfluenza viruses (PIVs) account for a large percentage of pediatric respiratory infections, including upper respiratory tract infections (URTIs), laryngotracheobronchitis (croup), bronchiolitis, and pneumonia. Human parainfluenza viruses is the major cause of croup (type 1 is most frequent, followed by type 3 and type 2). Human parainfluenza viruses are divided into 4 types, all of which are classified as paramyxoviruses. Infections from types 1 and 3 account for most disease. 

Transmission electron micrograph of parainfluenza virus. Transmission electron micrograph of parainfluenza virus. Two intact particles and free filamentous nucleocapsid.

Pathophysiology

The virus colonizes the nose and the nasopharynx; then, it invades the epithelium, resulting in cell damage, edema, and loss of cilia. A fibrinous exudate develops with downward spread of cell damage and edema. The resulting airway obstruction and laryngeal muscle spasm account for the typical symptoms of croup. The incubation period is 1-7 days.

Frequency

United States

Outbreaks of parainfluenza disease occur regularly throughout fall and mid winter. Parainfluenza virus type 1 causes biennial epidemics in the United States.

Mortality/Morbidity

Most children with croup have mild infections that are usually managed on an outpatient basis. Approximately 41,000 individuals per year are admitted to the hospital for parainfluenza virus infections. Precautions are necessary within hospitals to prevent further spread.^{[3 ]}Only 1-5% of patients admitted to the hospital need artificial airway support.

Age

Parainfluenza-related laryngotracheobronchitis commonly affects children aged 3 months to 3 years. Parainfluenza virus infection can also account for bronchiolitis in infants and children younger than 2 years.

Clinical

History

• Patients with parainfluenza virus (PIV) infection typically present with a history of coryza and low-grade fever. They then develop the classic barking cough associated with croup.
• Symptoms of croup include the following:
  • Fever
  • Barking cough
  • Coryza
  • Stridor
  • Retractions
  • Tachypnea (when lower airways become involved)
  • Irritability
• Children with croup are usually more symptomatic at night. Coughing often awakens them from sleep. The reasons for worsening of symptoms at night are unknown.
• Parainfluenza infections can also present as bronchiolitis. The typical presentation includes fever, coryza, tachypnea, coughing, and wheezing.^{[4 ]}

Physical

• Croup scoring systems have been developed to aid in grading the severity of infection.
• Factors in such scoring systems include stridor, retractions, air entry, color, and level of consciousness.
• Croup scoring systems were developed prior to the advent of pulse oximetry. Pulse oximetry may be beneficial in grading severity of illness, response to management, and disposition.

Differential Diagnoses

Epiglottitis
Retropharyngeal Abscess

Other Problems to Be Considered

Tracheitis
Pneumonia

Workup

Laboratory Studies

• Viral cultures in patients with parainfluenza virus (PIV) infection usually require 4-7 days to yield results, which limits their clinical applicability in the acute setting. Cultures can be helpful from an epidemiological standpoint.
• Immunofluorescent and enzyme immunoassay methods can be performed to test nasopharyngeal washings; however, they are not readily available and vary in sensitivity.
• The WBC count on CBC count samples is usually normal; however, lymphocytosis may be noted.

Imaging Studies

• Posteroanterior (PA) radiography of the neck may reveal the classic steeple sign (ie, narrowing of the proximal portion of the trachea, indicative of subglottic edema); however, this finding is absent in approximately 50% of cases.
• Lateral soft tissue films of the neck are normal in most cases. Lateral neck films can be useful if the diagnosis is unclear, especially if conditions such as foreign body aspiration, retropharyngeal abscess, or epiglottitis are in the differential diagnosis.

Treatment

Medical Care

Management of croup caused by parainfluenza virus (PIV) infection depends on the severity of disease.

• Prehospital care
  • Prehospital care includes fever control and attempts to alleviate respiratory symptoms and patient anxiety.
  • Respiratory symptoms commonly improve with benign measures such as sitting in a bathroom with a steaming shower and allowing vapor droplets to soothe inflamed airways. Another option includes exposing the child to the cool night air. Often, the patient's symptoms resolve en route to the hospital. Attempts at calming or distracting the child can be beneficial.
  • Antipyretics may assist with fever control. Moderate or severe croup requires medical evaluation in the office or emergency department.
• Emergency department care
  • Mild croup: Management of mild croup consists of cool blow-by oxygen mist, fever control, and observation to determine whether the airway appears compromised.
  • Moderate croup
    • Cool oxygen mist and steroids are common therapies. Controlled trials for the palliation of croup symptoms have yielded conflicting results, and routine use of dexamethasone in this disease remains controversial. Dexamethasone was traditionally intramuscularly administered; however, recent studies have documented the use of oral steroids.
    • In patients who fail to improve, administration of racemic epinephrine with a nebulizer has been beneficial. If racemic epinephrine alleviates symptoms, observe the patient for a minimum of 3 hours to ensure the patient's condition does not worsen (eg, due to possible rebound laryngospasm as the racemic epinephrine dose wears off). If asymptomatic at this time, the patient can be discharged with proper follow-up care.
    • In patients with moderate croup, oral intake may be lacking; therefore, evaluate the patient's hydration status. Intravenous fluids may be required.
  • Severe croup
    • Perform the same measures as in moderate croup. Observe for signs of impending respiratory failure.
    • Repeat racemic epinephrine nebulization may be needed, in addition to intensive care monitoring. Racemic epinephrine nebulizations can be repeated at 1-hour to 2-hour intervals as needed. Fortunately, fewer than 5% of patients who are admitted require artificial airway support (endotracheal intubation).

Medication

No specific antiviral agents are available for treating parainfluenza virus (PIV) infections; however, medications are available to treat the respiratory symptoms associated with croup. The medications include corticosteroids and nebulized epinephrine to treat airway inflammation and edema.

Glucocorticoids

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. They modify the body's immune response to diverse stimuli. Anti-inflammatory drugs (specifically dexamethasone) help reduce the inflammation and subglottic edema of croup. Despite delayed onset of action, the high potency and prolonged intramuscular half-life of dexamethasone make it the preferred corticosteroid for croup.

Dexamethasone (Decadron)

Criterion standard anti-inflammatory drug for reducing airway edema that occurs in croup. Other glucocorticoids have been used, including prednisone and prednisolone. Dexamethasone is thought to decrease inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Dosing

Adult

10 mg PO/IV/IM qd

Pediatric

0.6 mg/kg PO/IM qd prn; not to exceed 10 mg/d

Interactions

Possible decreased effects with coadministration of barbiturates, phenytoin, or rifampin; decreases effect of salicylates and vaccines

Contraindications

Documented hypersensitivity; immunosuppressed patients receiving corticosteroids; varicella

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in hyperthyroidism, osteoporosis, cirrhosis, nonspecific ulcerative colitis, peptic ulcer, diabetes, and myasthenia gravis; tuberculosis; untreated systemic infections; ocular herpes simplex virus

Budesonide (Pulmicort Respules)

Nebulized budesonide has been found to be beneficial in treating croup.

Dosing

Adult

Not applicable

Pediatric

2-4 mg/d inhaled via nebulizer divided qd/bid

Interactions

Ketoconazole may increase plasma levels of budesonide; cimetidine may increase bioavailability of budesonide

Contraindications

Documented hypersensitivity; immunosuppressed patients receiving corticosteroids; varicella; patients may develop PO thrush

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Tuberculosis, untreated systemic infections, ocular herpes simplex virus

Prednisolone (Delta-Cortef, Pediapred)

Many practitioners administer liquid prednisolone for patients with croup in lieu of dexamethasone. Prednisolone has not been proven superior to dexamethasone.

Dosing

Adult

Not applicable

Pediatric

1-2 mg/kg/d PO qd or divided bid

Interactions

Decreases effects of salicylates and toxoids (for immunizations); phenytoin, carbamazepine, barbiturates, and rifampin decrease effects of corticosteroids

Contraindications

Documented hypersensitivity; immunosuppressed patients receiving corticosteroids; varicella

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Caution in hyperthyroidism, osteoporosis, cirrhosis, nonspecific ulcerative colitis, peptic ulcer, diabetes, and myasthenia gravis; tuberculosis; untreated systemic infections; ocular herpes simplex virus

Bronchodilators

When delivered by air or oxygen-powered devices, epinephrine is directly delivered to respiratory mucosal surfaces and smooth muscle. Because nebulizers deliver the medication directly to the target organ, fewer systemic adverse effects are encountered in comparison with oral or parenteral administration.

Epinephrine, racemic solution (Vaponefrin, microNefrin)

Very effective in reversing upper airway edema when administered with a nebulizer. Proposed mechanism of action is alpha-adrenergic receptor-mediated vasoconstriction of edematous tissues.

Dosing

Adult

Mix 0.5 mL with 3 mL 0.9% NaCl (normal saline) and inhale via nebulizer q1-2h prn

Pediatric

Mix 0.05 mL/kg with 3 mL 0.9% NaCl (normal saline) and inhale via nebulizer q1-2h prn; not to exceed 0.5 mL/dose

Interactions

Inhaled anesthetics may enhance cardiac irritability; nonselective beta-blockers block the beta effects of epinephrine leaving unopposed alpha effects (eg, hypertension)

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Tachycardia, especially with HR >200 BPM; consider cardiac monitoring if multiple doses required

L-epinephrine (Adrenalin)

In concentrations of 1:1000, may be substituted for racemic epinephrine for nebulized administration.

Dosing

Adult

5 mL nebulized q1-2h prn; mix with 3 mL 0.9% NaCl

Pediatric

<4 years: Mix 2.5 mL with 3 mL 0.9% NaCl (normal saline) and inhale via nebulizer
>4 years: Administer as in adults

Interactions

Inhaled anesthetics may enhance cardiac irritability; nonselective beta-blockers block the beta effects of epinephrine leaving unopposed alpha effects (eg, hypertension)

Contraindications

Documented hypersensitivity

Precautions

Pregnancy

C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus

Precautions

Tachycardia, especially with HR >200 BPM, consider cardiac monitoring if multiple doses required

Follow-up

Further Inpatient Care

Indications for hospitalization in patients with parainfluenza virus (PIV) infection include the following:

• Stridor or retractions present at rest despite therapy
• Need for repeated doses of racemic epinephrine
• Rebound laryngospasm in patients who receive racemic epinephrine
• Signs of respiratory distress
• Inadequate oral intake or dehydration

Further Outpatient Care

• Use cool mist vaporizers.
• Administer acetaminophen or ibuprofen for fever.
• Increase oral fluid intake.

Deterrence/Prevention

• No vaccine is currently available for parainfluenza virus.
• Passively acquired maternal antibodies from breast feeding may be protective in the first few months of life.
• Handwashing and contact precautions can limit the spread of disease to others.

Complications

• Posttransplant parainfluenza virus infection is a cause of serious lower respiratory tract involvement in both adults and children who undergo bone marrow transplantation.
• Long-term ribavirin therapy has been helpful in case reports.^{[5 ]}

Prognosis

• Patients with parainfluenza infections generally do well, with resolution of symptoms in 7-10 days.
• On occasion, the infection spreads to the lower respiratory tract, causing bronchiolitis or viral pneumonia.
• Denudation of respiratory epithelium places patients at a slightly increased risk of bacterial superinfection. Evaluate any patient recovering from croup who deteriorates suddenly for possible bacterial tracheitis.

Patient Education

• For excellent patient education resources, visit eMedicine's Lung and Airway Center. Also, see eMedicine's patient education article Croup.

Miscellaneous

Medicolegal Pitfalls

• A common occurrence in pediatric emergency department charts concerns varied assessment of the patient. All notes on the chart (eg, triage, nursing, resident) should be examined. If the assessments differ from the physician's assessment, the physician should address said differences in his or her notes. At discharge, ensure that proper discharge instructions, both written and oral, are given to the patient.
• Document an examination at time of discharge. For example, "Patient is breathing comfortably, is alert, consolable, without tachypnea, stridor, or retractions." A pulse oximetry reading can also be included if available.
• If the patient has a pediatrician or other primary care provider, attempt to contact them to ensure proper follow-up care. The pediatrician can also be consulted on management issues if the physician has concerns or doubts.
• For any concerns about stability for discharge, always err on the side of admission.

Multimedia

Media file 1: Transmission electron micrograph of parainfluenza virus. Transmission electron micrograph of parainfluenza virus. Two intact particles and free filamentous nucleocapsid.

References

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2. Manning A, Russell V, Eastick K, et al. Epidemiological profile and clinical associations of human bocavirus and other human parvoviruses. J Infect Dis. Nov 1 2006;194(9):1283-90. [Medline].

3. [Guideline] Standard precautions in hospitals. In: Betsy Lehman Center for Patient Safety and Medical Error Reduction, JSI Research and Training Institute, Inc. Prevention and control of healthcare-associated infections in Mass. Part 1: final recommendations of the Expert Panel. Massachusetts Department of Public Health; 2008 Jan 31. p. 42-9. [Full Text].

4. Lopez Perez G, Morfín Maciel BM, Navarrete N, Aguirre A. Identification of influenza, parainfluenza, adenovirus and respiratory syncytial virus during rhinopharyngitis in a group of Mexican children with asthma and wheezing. Rev Alerg Mex. May-Jun 2009;56(3):86-91. [Medline].

5. Stankova J, Carret AS, Moore D, et al. Long-term therapy with aerosolized ribavirin for parainfluenza 3 virus respiratory tract infection in an infant with severe combined immunodeficiency. Pediatr Transplant. Mar 2007;11(2):209-13. [Medline].

6. Barkin RM. Respiratory disorders. In: Pediatric Emergency Medicine Concepts Clinical Practice. 1993.

7. Cressman WR, Myer CM 3rd. Diagnosis and management of croup and epiglottitis. Pediatr Clin North Am. Apr 1994;41(2):265-76. [Medline].

8. Cruz MN, Stewart G, Rosenberg N. Use of dexamethasone in the outpatient management of acute laryngotracheitis. Pediatrics. Aug 1995;96(2 Pt 1):220-3. [Medline].

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10. Donaldson D, Poleski D, Knipple E, et al. Intramuscular versus oral dexamethasone for the treatment of moderate-to-severe croup: a randomized, double-blind trial. Acad Emerg Med. Jan 2003;10(1):16-21. [Medline].

11. Kairys SW, Olmstead EM, O'Connor GT. Steroid treatment of laryngotracheitis: a meta-analysis of the evidence from randomized trials. Pediatrics. May 1989;83(5):683-93. [Medline].

12. Klassen TP, Watters LK, Feldman ME, et al. The efficacy of nebulized budesonide in dexamethasone-treated outpatients with croup. Pediatrics. Apr 1996;97(4):463-6. [Medline].

13. Prendergast M, Jones JS, Hartman D. Racemic epinephrine in the treatment of laryngotracheitis: can we identify children for outpatient therapy?. Am J Emerg Med. Nov 1994;12(6):613-6. [Medline].

14. Rittichier KK, Ledwith CA. Outpatient treatment of moderate croup with dexamethasone: intramuscular versus oral dosing. Pediatrics. Dec 2000;106(6):1344-8. [Medline].

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17. Wendt CH, Weisdorf DJ, Jordan MC, Balfour HH Jr, Hertz MI. Parainfluenza virus respiratory infection after bone marrow transplantation. N Engl J Med. Apr 2 1992;326(14):921-6. [Medline].

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Keywords

parainfluenza virus infection, PVI, croup, upper respiratory tract infection, laryngotracheobronchitis, URTI, severe acute respiratory syndrome, SARS, pneumonia, parainfluenza virus, coryza, cough, bronchiolitis, paramyxovirus, human bocavirus, treatment, diagnosis

Contributor Information and Disclosures

Author

Roy M Vega, MD, Assistant Professor of Pediatrics, Albert Einstein College of Medicine; Director, Pediatric Emergency Services, Department of Emergency Medicine, Bronx Lebanon Hospital Center, Bronx, NY
Roy M Vega, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Medical Editor

Ashir Kumar, MBBS, MD, FAAP, Professor, Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University; Consulting Staff, Department of Pediatrics, EW Sparrow Hospital
Ashir Kumar, MBBS, MD, FAAP is a member of the following medical societies: American Academy of Pediatrics, American Association of Physicians of Indian Origin, American Federation for Clinical Research, American Society for Microbiology, Infectious Diseases Society of America, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Joseph Domachowske, MD, Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York-Upstate Medical University
Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa
Disclosure: Nothing to disclose.

CME Editor

Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

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