A surge in human metapneumovirus paediatric respiratory admissions in Western Australia following the reduction of SARS-CoV-2 non-pharmaceutical interventions

Aim: Western Australian laboratory data demonstrated a decrease in human metapneumovirus (hMPV) detections through 2020 associated with SARS-CoV-2-related non-pharmaceutical interventions (NPIs), followed by a subsequent surge in metropolitan region in mid-2021. We aimed to assess the impact of the surge in hMPV on paediatric hospital admissions and the contribution of changes in testing. Methods: All respiratory-coded admissions of children aged <16 years at a tertiary paediatric centre between 2017 and 2021 were matched with respiratory virus testing data. Patients were grouped by age at presentation and by ICD-10 AM codes into bronchiolitis, other acute lower respiratory infection (OALRI), wheeze and upper respiratory tract infection (URTI). For analysis, 2017–2019 was utilised as a baseline period. Results: hMPV-positive admissions in 2021 were more than 2.8 times baseline. The largest increase in incidence was observed in the 1–4 years group (incidence rate ratio (IRR) 3.8; 95% confidence interval (CI): 2.5–5.9) and in OALRI clinical phenotype (IRR 2.8; 95% CI: 1.8–4.2). The proportion of respiratory-coded admissions tested for hMPV in 2021 doubled (32–66.2%, P < 0.001), with the greatest increase in wheeze (12–75% in 2021, P < 0.001). hMPV test percentage positivity in 2021 was higher than in the baseline period (7.6% vs. 10.1% in 2021, P = 0.004). Conclusion: The absence and subsequent surge underline the susceptibility of hMPV to NPIs. Increased hMPV-positive admissions in 2021 can be partially attributable to testing, but test-positivity remained high, consistent with a genuine increase. Continued comprehensive testing will help ascertain true burden of hMPV respiratory diseases. © 2023 The Authors. Journal of Paediatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).