Human Parainfluenza Viruses (HPIVs) What are human parainfluenza
viruses? Human parainfluenza viruses (HPIVs) are a group of
viruses that cause different types of respiratory infections and
are most common in children and babies. Most HPIVs usually cause
infections of the upper airway such as a common cold, ear
infections, or sore throat. Other infections caused by HPIVs
include infections of the lower respiratory tract such as croup
(an infection of the airway below the larynx, or "voice box,"
that is characterized by a barky cough and harsh, noisy
breathing), pneumonia, or bronchiolitis (an inflammation of the
lower airways). Croup outbreaks usually occur during the fall
season and tend to be worse ever other year. Lower respiratory
tract infections occur during the spring and summer and often
continue into the fall. Children between the ages of 3 months
and 5 years are most likely to develop croup. Children under the
age of 2 are more likely to develop lower respiratory tract
infections such as pneumonia o