Skip Navigation

Center for Immunization Research

Left Background

HPIV (human parainfluenza virus)

Human parainfluenza viruses types 1, 2, and 3  (HPIV-1, HPIV-2, and HPIV-3) are the second most common causes of lower respiratory tract disease in infants and young children.  Parainfluenza 1 and 2 are the leading causes of croup, and parainfluenza type 3, like RSV, is an important cause of bronchiolitis and pneumonia in young infants. Most children are infected by HPIV-3 by the age of two years and by HPIV-1 and HPIV-2 by the age of five years. HPIV-1 is estimated to account for 16,300 to 96,500 annual hospitalizations in the US. Along with RSV, parainfluenza viruses are also leading causes of hospitalization in adults with community-acquired respiratory disease.

HPIV Resources

Centers for Disease Control and Prevention
National Center for Infectious Diseases, Respiratory and Enteric Viruses Branch

World Health Organization
Initiative for Vaccine Research



Pandemic Influenza


Respiratory Viruses Vaccine Trials