Available online 15 March 2023

Author links open overlay panel, , , , , , AbstractBackground

Parainfluenza virus type 3 (PIV-3) is one of the common pathogens for respiratory infections in children. Whether viral load of PIV-3 is associated with severity of respiratory diseases in children is not yet known. Our aim was to determine significance of PIV-3 viral load among infected children.

Methods

We conducted a single-center, retrospective study at Tokyo Metropolitan.

Children's Medical Center, Japan, from June to August 2021. Hospitalized children were screened with a posterior nasal swab for multiplex PCR, and viral load was subsequently measured from remained samples by real-time PCR. Demographic data were collected from digital charts. PIV-3 positive patients were categorized into mild group with no oxygen demand, moderate group with low-flow oxygen demand and severe group with high-flow nasal cannula oxygen or non-invasive positive pressure ventilation or mechanical ventilation. Viral loads were compared among mild, moderate and severe groups.

Results

151 patients were positive for PIV-3. We found no statistically significant association among PIV-3 viral load and severity of respiratory diseases (p = 0.35), and no statistically significant association between severity of illness and co-detection of other viruses. In each severity group, relatively high viral load per posterior nasal swab was observed at the time of testing.

Conclusion

Among PIV-3 patients, we could not find statistically significant between viral load and their severity, therefore we could not conclude that viral load is a good surrogate marker for clinical severity of PIV-3.

Section snippetsFunding

Tokyo metropolitan research grant

Authorship statement

Contributors Mami Ichinose was responsible for the organization and coordination of the trial. Keiko Soneda, Meiwa Shibata, Kazue Kinoshita, Hiroshi Hataya, and Yuho Horikoshi developed the trial design and revised critically for important intellectual content. Kento Ikegawa was responsible for the data analysis. All authors contributed to the writing of the final manuscript.

Study design and data collection

The present, retrospective study was conducted at Tokyo Metropolitan Children's Medical Center in Japan from June 2021 to August 2021. Pediatric inpatients were screened using a posterior nasal swab for PIV-3 for analysis using automated multiplex PCR. Specimens were collected at the time of admission. All positive samples were subsequently quantified for the viral load using real-time PCR. The exclusion criteria were refusal to participate in the study, positivity for PIV-3 within four weeks

Characteristics and clinical course of PIV-3 infection

Between June 2021 and August 2021, nasal swab samples were collected from 773 patients. PIV-3 was detected in 155 samples, and 135 patients were enrolled (Fig. 1). Table 1 shows the details of the clinical characteristics, symptoms, and laboratory data. Respiratory diseases were categorized into upper respiratory tract infections (34.1%), bronchitis or bronchiolitis (30.3%), pneumonia (9.8%), and asthma (3.8%). Asymptomatic cases and febrile cases without respiratory symptoms accounted for 6.8%

Discussion

The present study found no association between viral load and the severity of PIV-3 infection in children. This is the largest study of PIV3 infection conducted in a developed country. In each severity group, a relatively high viral load per posterior nasal swab (median 7log10 copies/mL) was observed at the time of testing. PIV-3 seemed to replicate well in the upper respiratory tract within the first week after illness onset regardless of clinical severity (Fig. 3, B). Notably, the PIV-3 viral

Declaration of competing interest

None.

In conducting the research, we received approval from the hospital's Ethics Committee.

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© 2023 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.