Human Parainfluenza Viruses (HPIV) and Other Parainfluenza Viruses Clinical Presentation

Updated: Sep 30, 2020
  • Author: Subhash Chandra Parija, MD, MBBS, PhD, DSc, FRCPath; Chief Editor: Michael Stuart Bronze, MD  more...
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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 to 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. [19]

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. [20]

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 [21] :

  • 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. [22] 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
  • Fatal pneumonia
  • Prolonged viral shedding
  • Rare complications, including Guillain-Barré syndrome and meningitis

Long-term ribavirin therapy has been helpful in case reports. [23]