Accurate and timely diagnoses of respiratory illnesses strengthen antimicrobial stewardship

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Every winter virus season is unique, especially influenza trends. Well-established global influenza surveillance systems aim to gauge, predict, report and ultimately provide guidance for protection (vaccine development) for the upcoming influenza season. 

By Dr Sudha Pottumarthy-Boddu
Dr Sudha Pottumarthy-Boddu has a distinguished career in microbiology with extensive experience in the US New Zealand and Australia. Sudha is a Diplomate of the American Board of Medical Microbiology, and a member of both the Antimicrobial Stewardship Committees and Infection Prevention and Control Committees at multiple St John of God hospitals in WA.

The ongoing COVID-19 pandemic adds another layer of complexity in making an accurate clinical diagnosis of winter respiratory illness, necessitating a robust, multiplex respiratory PCR assay to enable accurate and timely diagnosis and pathogen-directed specific therapy.

How COVID-19 has influenced antimicrobial resistance 

The 2022 Special Report COVID-19 U.S. Impact on Antimicrobial Resistance by the Centers for Disease Control and Prevention (CDC) found the impact of the pandemic on alarming trends in antibiotic resistance and on antibiotic prescribing practices. This is attributed to the pandemic, which pushed healthcare facilities and health departments in the US near their breaking points, with a significant increase in antimicrobial use and difficulties in following infection prevention and control guidance. 

Resistant hospital-onset infections and deaths increased by at least 15% during the first year of the pandemic, 2019 versus 2020. The increase in hospital onset-infections due to resistant pathogens varied from 13% for MRSA, 32-35% for ESBL-producing Enterobacterales, carbapenem-resistant Enterobacterales and multi-drug resistant P.aeruginosa to 78% increase for carbapenem-resistant Acinetobacter sp. 

The pandemic also impacted antibiotic prescribing, where antibiotics were often the first treatment prescribed for any febrile pulmonary illness, which often turned out to be COVID-19, a viral illness where antibiotics had no effect. The importance of preserving and prolonging the efficacy of the currently available antibiotics by being responsible antibiotic stewards is emphasised. 

Influenza statistics for 2023 

The Australian Influenza Surveillance report #08, 2023, noted 174,898 laboratory-confirmed influenza cases, with 162 influenza-associated deaths identified in the year-to-date in the NNDSS (National Notifiable Diseases Surveillance System).  Of the laboratory-confirmed influenza notifications Australia-wide in 2023, 62.64% were influenza A, with influenza B accounting for 35.19% of notifications (the rest being mixed infections or untyped).

This is in contrast to the reported influenza season notifications of 2022 (National 2022 Influenza Season Summary), where influenza B accounted for only 0.2% of influenza notifications, the majority being influenza A (82.7%). Unlike influenza A viruses, which are also found in several different animals (ducks, chickens, pigs, whales etc.), influenza B viruses circulate widely only among humans.

Influenza notifications in WA from January 1 to July 23, 2023, reflect trends not dissimilar to the national data. Of the 15,280 influenza notifications during this period, 75% were influenza A, 24% influenza B and 1% untyped (Surveillance and Disease Control Program, Communicable Disease Control Directorate). The trend data of PCR positive influenza detections at PathWest 2022-2023, also depicts the continuing presence of circulating influenza B virus throughout this year-to-date, differing from that in 2022 (Fig 1).

Given the ongoing influenza notifications in Australia in 2023, in the face of resumed worldwide travel and limited social restrictions, the trends of winter respiratory illnesses continue to evolve over the season. The use of the multiplex respiratory PCR assay allows for an accurate and timely diagnosis of respiratory viral illness, early administration of appropriate antivirals if indicated, and at the same time limits the unnecessary use of antibiotics.  

Acknowledgements: We thank Cara Minney-Smith, Kritu Panta, Avram Levy and staff of the Microbial Surveillance Unit at PathWest Laboratory Medicine, Perth, WA, for providing influenza subtyping data.

– References available on request

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