Clinical Syndromes and Epidemiology - Parainfluenza Virus

Clinical Syndromes

Human parainfluenza viruses cause croup, pneumonia, bron-chiolitis and tracheobronchitis, and some other infections.

◗ Croup

Croup or laryngotracheobronchitis is a heterogeneous group of illnesses that affects the larynx, trachea, and bronchi. The condition manifests as fever, cough, laryngeal obstruction, and expiratory stridor. HPIV-1, HPIV-2, and HPIV-3 are the com-mon causes of croup; of which HPIV-1 is the most common.

◗ Pneumonia

HPIV-1 and HPIV-3 are responsible for most cases of human parainfluenza pneumonia. Fever, rales, and evidence of pulmo-nary consolidation are the common symptoms.

◗ Bronchiolitis and tracheobronchitis

Bronchiolitis is caused by all the five types of HPIV, but HPIV-1 and HPIV-3 are the most common causes. Most cases of bronchi-olitis occur in infants. The condition manifests as fever, expira-tory wheezing, tachypnea, and rales. HPIV-3 is more commonly associated with tracheobronchitis than HPIV-1 or HPIV-2.

◗ Other infections

Otitis media, pharyngitis, conjunctivitis, and coryza are the other infections caused by HPIV.

Epidemiology

Human parainfluenza viruses are ubiquitous.

◗ Geographical distribution

HPIVs (HPIV-1, HPIV-2, HPIV-3, and HPIV-4) have worldwide distribution. HPIV-1 is usually associated with epidemics of the disease.

Reservoir, source, and transmission of infection

Parainfluenza viruses cause disease exclusively in humans. No animal reservoirs are present. Respiratory secretions from the infected humans are the source of infection. The infection is transmitted by inhalation of respiratory droplets or by direct person-to-person contact with infected secretions.