Characterization of human parainfluenza virus-3 circulating in Israel, 2012-2015

Background: Human parainfluenza virus 3 (hPIV-3) causes respiratory tract infection. Objectives: The objective of this study was to describe the epidemiology of hPIV-3 infection among hospitalized patients and characterize the circulating strains. Study design: A cross-sectional study was conducted using respiratory samples of 15,946 hospitalized patients with respiratory symptoms in 2012–2015 in Israel. All samples were subjected to q-PCR and q-RT-PCR to determine the presence of hPIV-3 and other respiratory viruses. Samples positive for hPIV-3 were subjected to molecular typing and phylogenetic analysis. Results: Overall, 547 samples 3.4% (95% CI 3.2–3.7) were positive for hPIV-3. Of these 87 (15.9%) were mixed infections; 41.4% with adenovirus, 40.2% with RSV (40.2%) and 19.5% influenza A viruses. The prevalence of hPIV-3 was highest (5.1%) in children aged 0–4 years. Hospitalization in oncology department was associated with increased likelihood of hPIV-3 infection: adjusted odds ratio [aOR] 2.29 (95% confidence intervals [CI] 1.78–2.96), as well as hospitalization in organ transplantation department: aOR 3.65 (95% CI 2.80–4.76). The predominant lineages were C3c (62.3%) and C1b (24.6%), followed by sub-lineages C5 (8.7%) and C3b (2.9%). A new sub-lineage emerged in our analysis, named C1d, which was 17 (1.5%) nucleotide different from C1a, 25 (2.2%) nucleotide different from C1b and 24 (2.1%) nucleotide different from C1c. Discussion: Young children and immunocompromised patients are likely the risk groups for severe respiratory infections with hPIV-3. Strains belonging to lineages C3c and C1b, which are present worldwide, should be targeted in vaccine development. The emergence of new lineage might have public health implications and on vaccine development.