Estimates on the incidence rates of infections are needed to assess the burden of disease in the community.
To assess incidence rates of potentially serious infections in patients aged 65 years and over presenting to Flemish general practice from 2000 to 2015, and to describe patient characteristics.
We performed a retrospective study, based on data provided by the Intego morbidity registry of the KU Leuven, which includes the electronic medical records of 111 general practitioners. Incidence rates were calculated taking person-time at risk into account, and longitudinal trends from 2000 to 2015 were analysed using autoregressive time-series analyses.
On average, a person aged 65 years or older has an 8.0% risk of getting a potentially serious infection each year. Acute cystitis was the most often occurring potentially serious infection [39.8/1000 person-years; 95% confidence interval (CI): 39.4-40.2], followed by influenza like illness (ILI, 24.3/1000 person-years; 95% CI: 24.0-24.6) and pneumonia (9.7/1000 person-years; 95% CI: 9.5-9.9). The incidence rates of pneumonia were higher in older age groups and in men, whereas they were markedly lower for ILI at older ages, in both genders. From 2000 to 2015, overall incidence rates decreased significantly for ILI, while they increased in women for pneumonia, acute cystitis and pyelonephritis. Common chronic comorbidities were non-insulin dependent diabetes, chronic obstructive pulmonary disease, asthma, heart failure and chronic renal insufficiency.
Potentially serious infections are quite common in an older patient population presenting to primary care. They are accompanied by several chronic comorbidities, which may differ by infection type.

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