Parainfluenza is here

Yes, it’s getting to be that time of year.  At 4path, our Resp-20 RT-PCR panel has been detecting a large number of Para-influenza 1 cases from our pediatric practices.

Here is some brief information from Wikipedia on this class of viruses:

Human parainfluenza viruses (hPIVs) are the viruses that cause ‘human parainfluenza.’ hPIVs are a group of four distinct serotypes of enveloped single-stranded RNA viruses belonging to the paramyxovirus family. These viruses are closely associated with both human and veterinary disease.

hPIV remains the second main cause of hospitalisation in children under 5 years of age suffering from a respiratory illness (only respiratory syncytial virus causes more respiratory hospitalisations for this age group).

  • Human parainfluenza virus type 1 (hPIV-1) (most common cause of croup)
  • Human parainfluenza virus type 2 (hPIV-2) (causes croup and other upper and lower respiratory tract illnesses)
  • Human parainfluenza virus type 3 (hPIV-3) (associated with bronchiolitis and pneumonia)
  • Human parainfluenza virus type 4 (hPIV-4) (includes subtypes 4a and 4b)

Clinical significance

In the USA it is estimated that there are 5 million children with lower respiratory infections (LRI) each year. Estimates have shown that hPIV-1, hPIV-2 and hPIV-3 have been linked with up to a third of these infections. Upper respiratory infections (URI) are also important in the context of hPIV, however are caused to a lesser extent by the virus. The highest rates of serious HPIV illnesses occur among young children and surveys have shown that about 75% of children aged 5 or older have antibodies to HPIV-1.

For infants and young children it has been estimated that ~25% will develop ‘clinically significant disease.’

Repeated infection throughout the life of the host is not uncommon and symptoms of later breakouts include upper respiratory tract illness, such as cold and a sore throat. The incubation period for all four serotypes is 1 to 7 days. In immunosuppressed people, parainfluenza virus infections can cause severe pneumonia which can be fatal.

hPIV-1 and hPIV-2 have been demonstrated to be the principal causative agent behind croup (laryngotracheobronchitis) which is a viral disease of the upper airway and is mainly problematic in children aged 6–48 months of age. Biennial epidemics starting in Autumn are associated with both hPIV-1 and 2 however, hPIV-2 can also have yearly outbreaks. Additionally, HPIV-1 tends to cause biennial outbreaks of croup in the fall. In the United States, large peaks have presently been occurring during odd-numbered years.

hPIV-3 has been closely associated with bronchiolitis and pneumonia and principally targets those aged <1 year.

hPIV-4 remains infrequently detected. However, it is now believed to be more common than previously thought, but is less likely to cause severe disease. By the age of 10, the majority of children are sero-positive for hPIV-4 infection which may be indicative of a large proportion of asymptomatic or mild infections.

hPIV has also been linked with rare cases of virally caused meningitis and Guillain-Barré syndrome.

HPIVs are spread person to person by contact with infected secretions through respiratory droplets or contaminated surfaces or objects. Infection can occur when infectious material contacts mucous membranes of the eyes, mouth, or nose, and possibly through the inhalation of droplets generated by a sneeze or cough. HPIVs can remain infectious in airborne droplets for over an hour.

Overall, hPIV remains best known for its effects on the respiratory system and this appears to be where the majority of the focus has been upon.

Airway inflammation

The inflammation of the airway is a common attribute of hPIV infection. It is believed to occur due to the large scale up-regulation of inflammatory cytokines. Common cytokines which would be expected to be up-regulated include IFN–α, various other interleukins (IL–2, IL-6) and TNF–α. Various other chemokines and inflammatory proteins are also believed to be associated with the common symptoms of hPIV infection.

Recent evidence seems to suggest that viral specific antibodies (IgE) may be responsible for mediating large scale releases of histamine in the trachea which are believed to cause croup.


The body’s primary defense against hPIV infection remains humoral immunity. This is mainly directed against surface proteins which can be found on the virus.

Interactions with the environment

Parainfluenza viruses last only a few hours in the environment and are inactivated by soap and water. Furthermore, the virus can also be easily destroyed using common hygiene techniques and detergents, disinfectants and antiseptics.

The majority of transmission has been linked to close contact, especially in nosocomial infections. Chronic care facilities are also known to be transmission ‘hotspots’ with transmission occurring via aerosols, large droplets and also fomites (contaminated surfaces).

Please see the original article in Wikipedia for complete transcription and references:    This is a shortened version of the original article.  4path is not responsible for the information provided by Wikipedia.  Please consult outside references for complete information.

By |2016-12-15T17:24:43+00:00November 2nd, 2015|Uncategorized|Comments Off on Parainfluenza is here