65 years of influenza surveillance by a World Health Organization‐coordinated global network

The 1918 devastating influenza pandemic left a lasting impact on influenza experts and the public, and the importance of global influenza surveillance was soon recognized. The World Health Organization (WHO) Global Influenza Surveillance Network (GISN) was founded in 1952 and renamed to Global Influenza Surveillance and Response System in 2011 upon the adoption by the World Health Assembly, of the Pandemic Influenza Preparedness Framework for the Sharing of Influenza Viruses and Access to Vaccines and Other Benefits (“PIP Framework”). The importance of influenza surveillance had been recognized and promoted by experts prior to the years leading up to the establishment of WHO. In the 65 years of its existence, the Network has grown to comprise 143 National Influenza Centers recognized by WHO, 6 WHO Collaborating Centers, 4 Essential Regulatory Laboratories, and 13 H5 Reference Laboratories. The Network has proven its excellence throughout these 65 years, providing detailed information on circulating seasonal influenza viruses, as well as immediate response to the influenza pandemics in 1957, 1968, and 2009, and to threats caused by animal influenza viruses and by zoonotic transmission of coronaviruses. For its central role in global public health, the Network has been highly recognized by its many partners and by international bodies. Several generations of world‐renowned influenza scientists have brought the Network to where it is now and they will take it forward to the future, as influenza will remain a preeminent threat to humans and to animals.

main reservoir for influenza A viruses, as well as in pigs, a mammalian species that is susceptible to both avian and human influenza A viruses. 4,5 For 40 years, since 1977, the 2 influenza A virus subtypes, H1N1 and H3N2, have been cocirculating with influenza B viruses in the human population, and all 3 viruses have undergone significant evolution through antigenic drift over time. 6 Occasionally an animal influenza A virus or an animal-human reassortant influenza A virus may cause infection in humans who have had contact with infected animals. 4 If such a virus readily replicates in humans, and this virus acquires the ability to spread from human to human in the absence of immunity in large segments of the human population, such a virus may cause a global pandemic. Although influenza pandemics obviously have stricken humanity throughout history, the first convincing historical evidence for an influenza pandemic is from 1580. Before the late 19th century, 3 additional influenza pandemics were identified through accurate clinical and epidemiological descriptions in historical records. 7 Precise laboratory evidence is available only for the 4 pandemics that occurred after 1917.

| DE VELOPMENTSLE AD INGUPTOTHE FOUND INGOFTHEG IS R S(1947-1952)
Memories of the devastating impact of the Spanish flu pandemic in 1918 were still vividly present in the minds of the medical and scientific experts as well as the public when the first experiments with influenza vaccines were undertaken only a few years after the first human influenza viruses were isolated. 8 The growing understanding that annual influenza epidemics can contribute to significant morbidity and mortality in the population and the fear of another severe pandemic stimulated vaccine research. In the early 1940s, techniques for the isolation of influenza viruses in embryonated hens' eggs were refined, which opened the door for more systematic and larger vaccine trials. During these years, descendants of the influ-   12 The same year, the Bulletin of the WHO devoted an entire issue to influenza, underlining the importance of this common disease. 13 During these years, an increasing understanding of the health burden caused by influenza viruses, widening insight into the biology of these viruses and their antigenic diversity reinforced the need for systematic surveillance of globally circulating influenza viruses to mount an appropriate, timely response to seasonal and pandemic influenza.

| T WODEC ADE SAND2INFLUENZ A PANDEMI C S(1953-1972)
When the GISRS was established in 1952, 25 countries already had some influenza surveillance in place and were able to report data to WHO, and contributing laboratories in these countries were later Five years after its establishment, the Network faced its first major challenge, the 1957 pandemic, caused by an influenza A virus of the H2N2 subtype. In early May, the NIC in Singapore informed WHO that it had identified an influenza A virus that was antigenically very distinct from the influenza A(H1N1) viruses circulating during previous years. 14

| ANOTHER2 0YE AR S-THE REEMERG EN CEOFINFLUENZ AA(H1N1) VIRUS E SANDD IVERG EN CEOFINFLUENZ A BVIRUS E S(1973-1992)
The GISRS Network continued to grow and by the end of 1972,

| PANDEMI CTHRE ATS ,PANDEMI C PREPAREDNE SS ,ANDAPANDEMIC(1993-2 017)
Twenty-five years after the 1968 pandemic, the influenza community and public health experts agreed that it is not a question whether but rather when a next pandemic will happen. This thought catalyzed national and international activities toward better preparedness for the event of an influenza pandemic. In the early 1990s, accumulating data revealed that the death toll from the "Spanish Since the inception of GISRS, countless enthusiastic, widely respected scientists, supported by their technical and administrative staff, have ensured its success through a highly collaborative ethos and ongoing technical development and geographic expansion. In addition, regional and global meetings of GISRS laboratories organized by WHO substantially foster dissemination of important information and provide excellent opportunities to establish or reinforce contacts between members of the GISRS community and its partners. This highly developed influenza surveillance network has been commended by international political bodies, by national authorities, and the business world. [35][36][37] The most recent WHO Meeting of NICs was held in Geneva in July 2017 as to commemorate the 65th anniversary of the GISRS, to review its past, to reflect on its present situation, and to examine how to take the Network forward into a future with exciting scientific achievements and technical developments that will be required to meet new influenza threats and challenges. 10,38 One hundred years after the 1918 pandemic, we understand that influenza pandemics will strike at unpredictable times. The WHOcoordinated GISRS Network must remain alert to timely recognize potential threats and provide the world tools to minimize the impact of influenza epidemics and pandemics.