Asian Flu in Milan, 1957. A brief history of the first pandemic occurred after the discovery of Influenza A virus and its impact in a large Italian city

Asian flu emerged in southern China in the last months of 1956 and after reaching Singapore and Hong spread in the rest of the world. Phylogenetic studies subsequently revealed that the new virus, called H2N2, was the product of a reassortment of a H1N1 strain circulating in humans with an avian strain that contributed polymerase subunit 1 (PB1), hemagglutinin and neuraminidase coding genes. The peak of the epidemic in most European countries occurred in autumn 1957. Compared to the Spanish flu, mortality was significantly lower, with an estimated number of two million deaths and case-fatality rate below 0.2%. Excess mortality rates varied across countries, with the lowest observed in Europe and the highest in Latin America. Compared to previous years, mortality rate increased during pandemic in school-age children and young adults more than in the other age groups. In Italy, the cases peaked in October 1957 and it has been suggested that their actual number exceeded 8 million, i.e. one-sixth of the total Italian population at the time. However, from 1950 to 1957 no significant variation was observed either in the total number of deaths or in the annual death rates and the deaths occurred in 1957 were even fewer than in previous year. In Milan - the second largest city in Italy - over the three-year period from 1956 to 1958 an increase of just over 300 deaths was observed in 1957, compared with the approximately 140 expected. Deaths directly attributed to influenza were 178 out of the 28,020 deaths observed in the three-year period (6.3‰). Although Asian flu affected mostly young people and children worldwide, the majority of deaths attributed to influenza in Milan occurred among individuals over 55 years of age, predominantly males. Despite the large number of infections and deaths it caused, the impact of the new pandemic on mortality and global population growth has been limited and not comparable to with that of the 1918 pandemic. Nevertheless, Asian flu exerted a strong influence on healthcare organization worldwide. The new pandemic gave a strong final push towards overcoming the fragmentation of competences on health among different ministries with the establishment of the Ministry of Health in Italy.