Influenza Virus, the Plague That Will Continue to Return

This chapter focuses on the influenza virus. Even though the casualties, both military and civilian, were massive during World War I, deaths from the epidemic of influenza virus in 1918–1919 surpassed the war’s toll: some 40 to 50 million people died of influenza in less than a year. Although respiratory infection was a common companion of influenza during the 1918–1919 pandemic, pneumonia in young adults has been rare before and since. Over 80% of current and past deaths related to influenza have occurred in people over the age of 70, who most often die from secondary bacterial infections. Yet the risk is almost as great for patients of any age who suffer from chronic heart, lung, kidney, or liver disease; children with congenital abnormalities; or anyone undergoing transplant surgery or afflicted with AIDS. The last influenza pandemic recorded, the “swine flu” pandemic of 2009–2010, provided a scorecard of how far people have come in surveillance, epidemiology, vaccination, and treatments since the 1918–1919 pandemic and the four pandemics that followed.