۱٫ Background

۲٫ Objectives

۳٫ Study design

۴٫ Results

۵٫ Discussion

Funding

Ethics approval

Prior presentations of data

Declaration of Competing Interest

Appendix A. Supplementary data

References

Abstract

Background: Human parainfluenza viruses (HPIVs) cause upper and lower respiratory tract illnesses, most frequently among infants and young children, but also in the elderly. While seasonal patterns of HPIV types 1-3 have been described, less is known about national patterns of HPIV-4 circulation.

Objectives: To describe patterns of HPIVs circulation in the United States (US).

Study design: We used data from the National Respiratory and Enteric Virus Surveillance System (NREVSS), a voluntary passive laboratory-based surveillance system, to characterize the epidemiology and circulation patterns of HPIVs in the US during 2011-2019. We summarized the number of weekly aggregated HPIV detections nationally and by US census region, and used a subset of data submitted to NREVSS from public health laboratories and several clinical laboratories during 2015-2019 to analyze differences in patient demographics.

Results: During July 2011 – June 2019, 2,700,135 HPIV tests were reported; 122,852 (5%) were positive for any HPIV including 22,446 for HPIV-1 (18%), 17,474 for HPIV-2 (14%), 67,649 for HPIV3 (55%), and 15,283 for HPIV-4 (13%). HPIV testing increased substantially each year. The majority of detections occurred in children aged ≤ ۲ years (36%) with fluctuations in the distribution of age by type.

Conclusions: HPIVs were detected year-round during 2011-2019, with type-specific year-to-year variations in circulation patterns. Among HPIV detections where age was known, the majority were aged ≤ ۲ years. HPIV-4 exhibited an annual fall-winter seasonality, both nationally and regionally. Continued surveillance is needed to better understand national patterns of HPIV circulation.

Background

Human parainfluenza viruses (HPIVs) are enveloped, single-stranded RNA viruses in the Paramyxoviridae family with four antigenically distinct types known to infect humans: HPIV-1, HPIV2, HPIV-3, and HPIV-4 1 . HPIVs can cause a range of upper and lower respiratory tract illnesses including bronchitis, bronchiolitis, laryngotracheobronchitis (croup), and pneumonia 2 . HPIVs are the second most common cause of acute respiratory illness-related hospitalizations in children < 5 years of age, second only to respiratory syncytial virus (RSV). HPIVs account for approximately 7% of all hospitalizations for fever, acute respiratory illness (ARI), or both3 . Co-infections of HPIV and other respiratory viruses are common and may lead to more complicated and prolonged disease course, especially among children

Clinical presentation can vary by type; HPIV-1 and HPIV-2 commonly cause croup and coldlike symptoms and HPIV-3 is more often associated with bronchiolitis and pneumonia4 . HPIV-4 is less well-characterized, as it has been less commonly included in respiratory virus diagnostic panels, but has been suggested to have a similar clinical presentation as HPIV-3 3,5,6 . Infants, young children, the elderly, and those that are immunocompromised are at higher risk for severe HPIV illness. In healthy adults, HPIV illness is usually limited to mild upper respiratory track symptoms.