Seasonal changes of respiratory infections in Northern Finland 2019–2024: evaluation of different diagnostic tests in rapidly changing epidemiological environment

ABSTRACT In primary health care, respiratory tract infections (RTIs) are one of the major causes of seeking medical attention. Diagnostic RTI laboratory tests provide information for both treating an individual patient as well as more generally epidemiological disease distribution of a given infection. In the case of SARS-CoV-2 pandemic, a diagnostic qPCR assay was rapidly developed in 2020, and the virus-specific test was subsequently incorporated into multiplex PCR tests that also detect other common seasonally occurring viruses, including influenza A and B, and RS-virus. We provide here the data on epidemiological distribution of 23 microbes between 2019 and 2024 in Northern Finland. While coronavirus was the most prominent detected microbe, adenovirus, RS-virus, influenzas, Mycoplasma pneumoniae , Chlamydia pneumoniae , and Bordetella pertussis/parapertussis were also commonly detected microbes. The incorporation of multiplex PCR into diagnostics of RTI, particularly in primary health care, will provide more epidemiological data; however, the cost-effectiveness of laboratory tests compared with data availability remains to be clarified. IMPORTANCE Respiratory tract infections (RTIs) are one of the major causes of health care visits. The role of laboratory diagnostics is important, as RTIs have numerous etiological pathogens, and the clinical symptoms may be similar. The distinction between viral and bacterial infections is important to avoid unnecessary antibiotic treatments. The data from RTI testing provide a wide perspective on the epidemiological situation before, during, and after the COVID-19 pandemic and provides insights into the differences in detection rates between age groups.