Parainfluenza refers to a group of viruses known as human parainfluenza viruses (HPIVs) that cause respiratory infections in humans. These viruses can lead to a range of illnesses affecting the upper and lower respiratory tracts, including common colds, croup (a condition with a barking cough and breathing difficulty), bronchiolitis, bronchitis, and pneumonia
. There are four main types of HPIVs (HPIV-1, HPIV-2, HPIV-3, and HPIV-4), each associated with different patterns of illness and seasons. For example, HPIV-1 and HPIV-2 commonly cause croup, especially in children, while HPIV-3 is more often linked to pneumonia and bronchiolitis
. HPIV-4 is less common and does not have a clear seasonal pattern
. Parainfluenza viruses are highly contagious and can be transmitted through close contact with infected individuals or by touching contaminated surfaces and then touching the face. Symptoms typically appear 2 to 7 days after exposure and can include fever, cough, sore throat, runny nose, wheezing, and shortness of breath. While infections are usually mild in healthy adults, they can be severe and even life-threatening in young children, older adults, and people with weakened immune systems
. Parainfluenza infections are common, especially in children, with most adults showing evidence of past infection through antibodies. These viruses are distinct from influenza viruses despite the similarity in their names
. In summary, parainfluenza is a group of viruses causing respiratory illnesses ranging from mild colds to severe lung infections, particularly affecting young children and vulnerable populations
