Parainfluenza

Parainfluenza viruses cause upper and lower respiratory infections.

Widespread in infants and children and rare in adults, parainfluenza resembles influenza but is milder and seldom fatal. This self-limiting disease causes both upper and lower respiratory tract illness and is more common in children in the winter and spring.

Causes

Parainfluenza refers to any of a group of respiratory illnesses caused by paramyxoviruses, a subgroup of the myxoviruses. It's transmitted by direct contact or by inhalation of contaminated airborne droplets, and it has an incubation period of about 3 to 6 days.

Paramyxoviruses occur in four forms - Para 1 to 4 - that are linked to several diseases: croup (Para 1, 2, and 3), acute febrile respiratory illnesses (1, 2, and 3), the common cold (1, 3, and 4), pharyngitis (1, 3, and 4), bronchitis (1 and 3), and bronchopneumonia (1 and 3). Para 3 is the second most common infecting organism that causes lower respiratory tract infections in children (respiratory syncytial virus infection ranks first). Para 4 seldom causes symptomatic infections in humans.

By age 8, most children demonstrate antibodies to Para 1 and Para 3. Most adults have antibodies to all four types as a result of childhood infections and subsequent multiple exposures. Reinfection usually is less severe and affects only the upper respiratory tract.

Signs and symptoms

Symptoms may include:

• runny nose
• redness or swelling of the eyes
• barky cough
• noisy, harsh breathing
• hoarse voice or cry
• rattling felt over the chest or back
• wheezing
• fever
• irritability
• decreased appetite
• vomiting
• diarrhea

Diagnostic tests 

Parainfluenza usually is clinically indistinguishable from similar viral infections. Isolation of the virus and serum antibody titers differentiate parainfluenza from other respiratory illness, but they seldom are done.

Treatment

Parainfluenza may require no treatment, or it may require bed rest, antipyretics, analgesics, and antitussives, depending on the severity of symptoms. Vaporizers are helpful in mild croup. Admittance to a facility seldom is necessary unless complications, such as croup or pneumonia, develop.

Prevention

There are no vaccines available for parainfluenza. Infections are most common in fall and winter. Avoiding crowds to limit exposure during peak outbreaks may decrease the likelihood of infection.

Parainfluenza infections are most severe in infants and become less severe with age. Limiting exposure, such as occurs in day-care centers and full nurseries, may delay infection until the child is older.