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Parainfluenza Virus Clinical Presentation

  • Author: Subhash Chandra Parija, MBBS, MD, PhD, FRCPath, DSc; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
Updated: Oct 07, 2015


Human parainfluenza viruses (HPIVs) have been associated with every type of upper and lower respiratory tract illness, including common cold with fever, laryngotracheobronchitis (croup), bronchiolitis, and pneumonia. HPIVs are also a cause of community-acquired respiratory tract infections of variable severity in adults. The incubation period of HPIV infection generally lasts 1-7 days. Weinberg et al found that HPIV accounted for 6.8% of all hospitalizations for fever, acute respiratory illnesses, or both in children younger than 5 years.[13]

All HPIV types are strongly correlated with specific clinical syndromes, ages, and times of year, though the lack of epidemiologic data on HPIV-4a and HPIV-4b has so far prevented a clear understanding of the true clinical significance of these serotypes. HPIV-1 and HPIV-2 are the pathogens most commonly associated with croup, and HPIV-3 is the pathogen most commonly associated with bronchiolitis and pneumonia in infants and young children.[14]

Patients with HPIV 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 why symptoms are worse at night are unknown.

HPIV infections can also present as bronchiolitis or pneumonia. The typical presentation includes the following[15] :

  • Fever
  • Coryza
  • Tachypnea
  • Coughing
  • Wheezing

Physical Examination

HPIV infection is associated with a broad range of findings, which may include fever, nasal congestion, pharyngeal erythema, nonproductive to minimally productive cough, inspiratory stridor, rhonchi, rales, and wheezing.


Croup is a generic term that encompasses a heterogeneous group of illnesses affecting the larynx, trachea, and bronchi. It affects about 3% of children in a given year, usually between ages 6 months and 3 years.[16] HPIV-1 is the most common cause of croup; between them, HPIV-1, HPIV-2, and HPIV-3 account for almost 75% of all cases. Symptoms of croup include fever, hoarse barking cough, laryngeal obstruction, and inspiratory stridor.

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


All 5 serotypes of HPIV can cause bronchiolitis, but the ones most commonly associated with this condition are HPIV-1 and HPIV-3, each of which appears to cause 10-15% of bronchiolitis cases in nonhospitalized children. The incidence of bronchiolitis peaks during the first year of life (with 81% of cases occurring during this period) and then declines dramatically until it virtually disappears by school age. Predominant features include fever, expiratory wheezing, tachypnea, retractions, rales, and air trapping.


HPIV-1 and HPIV-3 each cause about 10% of outpatient pneumonia cases, but as with bronchiolitis, HPIV-3 causes a larger percentage of cases in hospitalized patients. HPIV-2 and HPIV-4 can both cause pneumonia, but the incidence of disease attributable to these serotypes is not well described. HPIV-1 infection has been associated with secondary bacterial pneumonias in elderly persons. Features of pneumonia include fever, rales, and evidence of pulmonary consolidation.


More than 25% of the agents identified as causing tracheobronchitis have been HPIVs. (HPIV-3 is more commonly associated with tracheobronchitis than HPIV-1 or HPIV-2 is.) Tracheobronchitis is the most common feature seen in persons with HPIV-4 infections.

Other infections

HPIVs routinely cause otitis media, pharyngitis, and conjunctivitis coryza, and these can occur either singly or in combination with a lower respiratory tract infection (LRTI). HPIV-3 is the most frequently reported HPIV associated with otitis media.

Infections in immunocompromised patients

The growing number of patients who receive intense immunosuppression after undergoing transplantation of bone marrow and solid organs has highlighted the role of HPIVs as potential opportunistic pathogens.

HPIV-2 causes giant cell pneumonia in persons with severe combined immunodeficiency diseases (SCIDs). HPIV-3 has been found in persons with SCIDs and acute myeloid leukemia (AML), as well as in patients who have undergone bone marrow transplantation (BMT). The natural history of HPIV in patients infected with HIV is generally less severe than that in transplant recipients.



Complications of HPIV infection may include the following:

  • Acute respiratory distress syndrome (ARDS) and exacerbation of nephritic syndrome
  • Serious morbidity in immunocompromised hosts (eg, transplant recipients) – Posttransplant HPIV infection is a cause of serious lower respiratory tract involvement in both adults and children who undergo BMT
  • Rare complications, including Guillain-Barré syndrome and meningitis

Long-term ribavirin therapy has been helpful in case reports.[17]

Contributor Information and Disclosures

Subhash Chandra Parija, MBBS, MD, PhD, FRCPath, DSc Director-Professor of Microbiology, Head of Department of Microbiology, Jawaharlal Institute, Postgraduate Medical Education and Research, India

Subhash Chandra Parija, MBBS, MD, PhD, FRCPath, DSc is a member of the following medical societies: Royal College of Pathologists, Indian Society for Parasitology, Indian Medical Association, National Academy of Medical Sciences (India), Indian Association of Medical Microbiologists, Indian Association of Biomedical Scientists, Indian Association of Pathologists and Microbiologists, Indian Academy of Tropical Parasitology

Disclosure: Received salary from Jawaharlal Institute of Postgraduate Medical education & Research , Pondicherry , India for employment.


Thomas J Marrie, MD Dean of Faculty of Medicine, Dalhousie University Faculty of Medicine, Canada

Thomas J Marrie, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, Association of Medical Microbiology and Infectious Disease Canada, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.

Chief Editor

Mark R Wallace, MD, FACP, FIDSA Clinical Professor of Medicine, Florida State University College of Medicine; Clinical Professor of Medicine, University of Central Florida College of Medicine

Mark R Wallace, MD, FACP, FIDSA is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, International AIDS Society, Florida Infectious Diseases Society

Disclosure: Nothing to disclose.


Jeffrey D Band, MD Professor of Medicine, Oakland University William Beaumont School of Medicine; Director, Division of Infectious Diseases and International Medicine, Corporate Epidemiologist, William Beaumont Hospital; Clinical Professor of Medicine, Wayne State University School of Medicine

Disclosure: Nothing to disclose.

Richard B Brown, MD, FACP Chief, Division of Infectious Diseases, Baystate Medical Center; Professor, Department of Internal Medicine, Tufts University School of Medicine

Richard B Brown, MD, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Chest Physicians, American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, and Massachusetts Medical Society

Disclosure: Nothing to disclose.

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.

Ashir Kumar, MD, MBBS, FAAP Professor Emeritus, Department of Pediatrics and Human Development, Michigan State University College of Human Medicine

Ashir Kumar, MD, MBBS, FAAP is a member of the following medical societies: American Association of Physicians of Indian Origin and Infectious Diseases Society of America

Disclosure: Nothing to disclose.

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: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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.

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

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