Do influenza epidemics spread to neighbouring countries?

This study compares the main causes of influenza epidemics reported in Czechoslovakia (CSR) and the German Democratic Republic (GDR) during the 9 seasons between 1980 and 1988. The influenza epidemics due to identical virus types were experienced in the two countries in the 1980, 1984 and 1986 seasons, and of these only the 1984 epidemic associated with A-strain influenza A/Chile/1/83 (H1N1) virus could be demonstrated to spread from the eastern parts of the CSR to the northern areas of the GDR. This implies that influenza epidemics due to identical drift variants spread only exceptionally from one country to the other during the period of observation, in spite of a busy tourist activity across the borderline.