Parainfluenza Virus Infection

name: Parainfluenza Virus Infection
creation_date: "2026-06-28T00:00:00Z"
description: >
  Parainfluenza virus infection is an acute respiratory infection caused by the
  human parainfluenza viruses (HPIV; enveloped, negative-sense single-stranded
  RNA viruses of the family Paramyxoviridae), divided antigenically and
  genetically into types 1 to 4. HPIV-1 to HPIV-3 are major causes of upper and
  lower respiratory tract infection in infants, young children, the
  immunocompromised, the chronically ill, and the elderly. Each type tends to
  cause somewhat distinct illness: HPIV-1 (and HPIV-2) are the leading viral
  causes of croup (laryngotracheobronchitis), while HPIV-3 is an important cause
  of bronchiolitis and pneumonia in infancy, second only to respiratory syncytial
  virus. The virus infects the ciliated respiratory epithelium and elicits an
  innate antiviral/interferon and inflammatory response that drives much of the
  symptomatic illness.
category: Infectious Disease
parents:
- Viral Respiratory Infection
synonyms:
- Human parainfluenza virus infection
- HPIV infection
- Parainfluenza
disease_term:
  preferred_term: parainfluenza infection
  term:
    id: MONDO:0100197
    label: parainfluenza infectious disease
pathophysiology:
- name: Respiratory Epithelial Infection and Innate Immune Response
  conforms_to: "innate_antiviral_interferon_response#Interferon-Stimulated Gene Antiviral State"
  description: >
    HPIV infects the ciliated epithelium of the upper and lower respiratory tract,
    where viral replication is sensed by the host innate immune system and triggers
    a type I/III interferon and inflammatory cytokine response. Much of the
    symptomatic illness reflects this host antiviral and inflammatory response
    together with epithelial injury. HPIV-1 to HPIV-3 are leading causes of lower
    respiratory tract infection in young children and other vulnerable hosts.
  cell_types:
  - preferred_term: respiratory epithelial cell
    term:
      id: CL:0002632
      label: epithelial cell of lower respiratory tract
  - preferred_term: ciliated airway epithelial cell
    term:
      id: CL:0000064
      label: ciliated cell
  biological_processes:
  - preferred_term: viral genome replication
    term:
      id: GO:0019079
      label: viral genome replication
  - preferred_term: defense response to virus
    term:
      id: GO:0051607
      label: defense response to virus
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  locations:
  - preferred_term: respiratory system
    term:
      id: UBERON:0001004
      label: respiratory system
  - preferred_term: lung
    term:
      id: UBERON:0002048
      label: lung
  evidence:
  - reference: PMID:12692097
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      HPIV-1 to HPIV-3 are major causes of lower respiratory infections in
      infants, young children, the immunocompromised, the chronically ill, and the
      elderly.
    explanation: >-
      Establishes HPIV-1 to HPIV-3 as major causes of lower respiratory tract
      infection in vulnerable hosts. Evidence source is OTHER as this is a review
      article.
  - reference: PMID:12692097
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      These viruses belong to the Paramyxoviridae family
    explanation: >-
      Identifies HPIV as members of the Paramyxoviridae family. Evidence source is
      OTHER as this is a review article.
  downstream:
  - target: Laryngotracheal Inflammation and Subglottic Narrowing
    description: >-
      In the larynx and subglottic airway, HPIV (especially type 1) infection and
      inflammation narrow the airway, producing croup.

- name: Laryngotracheal Inflammation and Subglottic Narrowing
  description: >
    HPIV infection of the larynx, trachea, and subglottic airway produces
    inflammatory edema that narrows the relatively small pediatric subglottis,
    causing the inspiratory stridor and barking cough of croup
    (laryngotracheobronchitis). HPIV-1 is the most frequent viral cause of croup;
    HPIV-2 also causes croup, while HPIV-4 is comparatively more associated with
    lower respiratory tract involvement.
  locations:
  - preferred_term: larynx
    term:
      id: UBERON:0001737
      label: larynx
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:38900074
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with the other serotypes, croup was significantly more common in
      PIV-1 and lower respiratory tract infection was significantly more common in
      PIV-4.
    explanation: >-
      Pediatric cohort data showing croup is significantly more common with HPIV-1
      and lower respiratory tract infection with HPIV-4. Evidence source is
      HUMAN_CLINICAL as this is a clinical cohort study.
  downstream: []
phenotypes:
- category: Respiratory
  name: Croup
  description: >
    Laryngotracheobronchitis with the characteristic barking ("seal-like") cough
    and inspiratory stridor, the hallmark presentation of HPIV-1 infection in young
    children.
  phenotype_term:
    preferred_term: Croup (barking cough)
    term:
      id: HP:0033121
      label: Barking cough
  evidence:
  - reference: PMID:38900074
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Compared with the other serotypes, croup was significantly more common in
      PIV-1 and lower respiratory tract infection was significantly more common in
      PIV-4.
    explanation: >-
      Supports croup as a characteristic, serotype-associated manifestation of
      parainfluenza (most common with HPIV-1). Evidence source is HUMAN_CLINICAL as
      this is a clinical cohort study.
- category: Respiratory
  name: Stridor
  description: >
    Inspiratory stridor from subglottic airway narrowing during croup.
  phenotype_term:
    preferred_term: Stridor
    term:
      id: HP:0010307
      label: Stridor
- category: Respiratory
  name: Bronchiolitis
  description: >
    Lower respiratory tract involvement with small-airway inflammation, especially
    with HPIV-3 in infants and HPIV-4.
  phenotype_term:
    preferred_term: Bronchiolitis
    term:
      id: HP:0011950
      label: Bronchiolitis
  evidence:
  - reference: PMID:12692097
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      HPIV-1 to HPIV-3 are major causes of lower respiratory infections in
      infants, young children, the immunocompromised, the chronically ill, and the
      elderly.
    explanation: >-
      Supports lower respiratory tract involvement (including bronchiolitis) as a
      manifestation of HPIV infection. Evidence source is OTHER as this is a review
      article.
- category: Respiratory
  name: Cough
  description: >
    Cough is a common manifestation of HPIV respiratory infection.
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
- category: Respiratory
  name: Rhinorrhea
  description: >
    Nasal discharge accompanies upper respiratory HPIV infection.
  phenotype_term:
    preferred_term: Rhinorrhea
    term:
      id: HP:0031417
      label: Rhinorrhea
- category: Constitutional
  name: Fever
  description: >
    Fever commonly accompanies acute parainfluenza infection.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
treatments:
- name: Supportive Care
  description: >
    Management of parainfluenza infection is largely supportive (hydration,
    antipyretics, and respiratory support as needed); no specific antiviral therapy
    is approved.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
- name: Corticosteroid Therapy for Croup
  description: >
    Croup is treated with corticosteroids (e.g., dexamethasone) to reduce
    subglottic airway inflammation, with nebulized epinephrine for
    moderate-to-severe airway obstruction.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: dexamethasone
      term:
        id: CHEBI:41879
        label: dexamethasone
  target_mechanisms:
  - target: Laryngotracheal Inflammation and Subglottic Narrowing
    treatment_effect: INHIBITS
    description: >-
      Corticosteroids suppress the laryngotracheal inflammatory edema that narrows
      the subglottic airway in croup, relieving stridor and respiratory distress.
notes: >
  Created as part of the Respiratory Infections project (Intercept-aligned endemic
  respiratory viruses). Conforms to the innate_antiviral_interferon_response
  module via the epithelial innate/interferon response node. The infectious_agent
  (NCBITaxon) block was omitted at creation; HPIV types 1-4 are described in the
  text and can be added later.