Figure 1.

Influenza detections among eligible patients presenting with influenza-like illness, by week of specimen collection, SPSN, Canada, 1 November 2022–6 January 2023 (weeks 44–1) (n = 1,490)

SPSN: Sentinel Practitioner Surveillance Network.

Among eligible patients presenting with influenza-like illness, influenza test-positive cases and test-negative controls are displayed by week of specimen collection in 2022/23. Tallies correspond with participant profiles shown below but with influenza A(H1N1)pdm09 and unsubtyped influenza A detections additionally displayed. Not displayed is a single influenza B detection in week 49. The figure excludes cases and controls vaccinated within 2 weeks of illness onset and those with missing information for covariates used in primary vaccine effectiveness analyses. As per usual SPSN approach, missing specimen collection dates were imputed as the date the specimen was received and processed at the laboratory minus 2 days.