… is and enveloped RNA virus belonging to the family Paramyxoviridae. Four distinct types have been identified (type-1 to type-4). PIV’s commonly cause general upper and lower respiratory illnesses. Symptoms of upper respiratory illness may include fever, runny nose, and cough. More severe lower respiratory illness includes croup, bronchitis, bronchiolitis and pneumonia. Croup is the signature clinical manifestation of infection with parainfluenza viruses. PIV infections have been suggested to worsen symptoms of chronic lung disease or asthma in children and adults.
PIV type-3 (PIV-3) is most common in very young children and is, besides RSV, one of the main causes of bronchiolitis and pneumonia in new-borns. PIV-1 and PIV-2 are most common in children aged two to five. Here PIV-1 is responsible for 30-50% of croup cases. PIV-4 has a lower incidence and mostly occurs in older children. These PIV-types vary in seasonal patterning. PIV-3 shows typical yearly incidence peaks in spring and summer, while PIV-1 and PIV-2 can show incidence peaks in autumn. Hence cyclic seasonal patterns of respiratory illness due to PIV infections are observed in Belgium, with a major peak in spring, but continuing transmission in autumn. PIVs spread from person to person through close personal contact, in the air by coughing and sneezing, and by touching contaminated objects or surfaces. Primary infection in immunocompetent children causes viral shedding from 1 week before up till 3 weeks after onset of symptoms, but immunodeficient patients often show prolonged periods of viral shedding. The period prior to symptom development after exposure ranges from 2 to 6 days. Young children are more likely to have severe illness, but older adults and people with weakened immune systems are also at risk. Parainfluenza viruses do not cause complete protective immunity, allowing re-infection, though subsequent infection usually causes mild illness. There is no specific antiviral therapy available for PIV illness and most people will recover on their own. Standard cough and hand hygiene are effective preventive measures for PIV infection.
Surveillance facts & reports
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- Henrickson KJ. Parainfluenza viruses. Clin Microbiol Rev 2003, 16:242-64.