Figure.

Number and incidence of laboratory-confirmed influenza cases, and number of patients hospitalised with influenza diagnosis in Stockholm County, influenza seasons 2011/12–2014/15

ICD: International Classification of Diseases.

Unadjusted incidence calculated by number of laboratory-confirmed cases per 100,000 inhabitants. Numbers reported by calendar week each season.

No data were available on number of laboratory-confirmed hospitalised influenza cases due to anonymous data in the central database for healthcare utilisation, making linkage impossible.

^a Data obtained from the Public Health Agency of Sweden

^b Data collected in Stockholm County’s central database for healthcare utilisation using ICD-10 codes J09-J11

^c (Number of laboratory-confirmed cases/number of inhabitants in Stockholm during season) × 100,000.