Matthias Maiwald^1,2,3  

¹Department of Pathology and Laboratory Medicine, KK Women’s and Children’s Hospital, Singapore; ²Duke-National University of Singapore Medical School, Singapore; ³Yong Loo Lin School of Medicine, National University of Singapore, Singapore 

 

Background: CoVID-19 pandemic response measures caused a broad decline of non-SARS-CoV-2 respiratory pathogens, but these did not return immediately when measures were lifted. We assessed the dynamics of pathogen decline and re-emergence in Singapore. 

Methods: Respiratory multiplex PCR data from a major women’s and children’s hospital from 2019 to 2024 were analysed. This included >100,000 results, mostly from paediatric patients. 

Results: Enterovirus/Rhinovirus rebounded first in September 2020, reaching high rates by late 2021-early 2022. Adenovirus followed closely, but peaked later in early 2023. RSV rose in February 2021, at much higher than pre-pandemic levels, reaching a peak by April 2022. Influenza A only reappeared mid-2022 after the Southern Hemisphere influenza season, presumably travel-associated. An unusual metapneumovirus peak occurred in October 2022. Bordetella pertussis returned in 2024, but only in low numbers. Mycoplasma pneumoniae returned in the second half of 2023 and reached high numbers throughout 2024. 

Conclusions: Pandemic response measures disrupted the usual patterns of respiratory pathogens, and the subsequent staggered relaxation affected their re-emergence. Nonenveloped viruses returned first, RSV had out-of-season peaks, adenovirus and metapneumovirus had unusual phases of high activity. Several pathogens returned at higher rates than pre-pandemic. Population-based immunological susceptibility and exposure patterns presumably played a role. 

 

Contribution Note: Following the disappearance and reappearance of respiratory pathogens during the COVID-19 pandemic was the author’s own original idea and contribution.