Epidemiology of influenza in Poland, 1947/57.

Two systems of influenza reporting in use in Poland are described; one involves weekly reports by the public health laboratories, the other quarterly reports on influenza absenteeism. A third, experimental, system of daily reports is used in Łódź. Data obtained by all three systems are compared in this assessment of influenza epidemiology in Poland. Study of the epidemics of the last decade leads the authors to the conclusion that a number of them were possibly caused by a local virus which had earlier "taken root" in the country rather than by a virus imported from neighbouring countries. Attention is drawn to the isolation in 1953 of a strain related to PR8, generally held to be no longer circulating by that date. For reasons given, it is thought unlikely that this isolation was due to a laboratory accident.