Samples
Primary respiratory samples were collected between October week 40/2019 and March week 14/2020 in the context of the Arbeitsgemeinschaft Influenza (AGI) virological sentinel, including nasal or throat swabs from a total of 5080 patients presenting with acute respiratory illness. Of these, 413 were A(H1N1)pdm09 positive. In addition, 471 influenza positive samples (isolates) were provided by diagnostic laboratories distributed all over Germany. Of these, 218 were A(H1N1)pdm09 positive (Supplemental Table 1).