ABSTRACT
Human parainfluenza virus (HPIV)is one of the most common pathogens of community acquired respiratory infection.The epidemiology and clinical features vary in different subtypes.HPIV also affect other systems except respiratory system.The sequences of nucleotide and amino acid showed high identity among the strains in the same type,while remaining some variation.Most research shows the variation associated with time and district.Hemagglutinin-neuraminidase(HN) protein shows most polymorphic among all the proteins of HPIV.Some amino acid variation among the active site of HN protein will affect its activity.The influence of many gene mutations,which lead to amino acid variation,and affect the activity of HN protein remains uncertain.Further study on the epidemiology,clinical features,phylogenetics analysis of HPIV plays an important role in the prevention and control of its prevalence.