Syndemic
The worst of the 20th century influenza pandemics was the 1918 pandemic, where between 20-40 percent of the world’s population became ill between 40-100 million people died. More people died of the so-called Spanish flu (caused by the H1N1 viral strain) pandemic in the single year of 1918 than during all four-years of the Black Death. The pandemic had devastating effects as disease spread along trade and shipping routes and other corridors of human movement until it had circled the globe. InIndia, the mortality rate reached 50 per 1,000 population. Arriving during the closing phase of the World War I, the pandemic impacted mobilized national armies. Half of U.S. soldiers who died in the "Great War," for example, were victims of influenza. It is estimated that almost ¾ of a million Americans died during the pandemic. In part, the death toll during the pandemic was caused by viral pneumonia characterized by extensive bleeding in the lungs resulting in suffocation. Many victims died within 48 hours of the appearance of the first symptom. It was not uncommon for people who appeared to be quite healthy in the morning to have died by sunset. Among those who survived the first several days, however, many died of secondary bacterial pneumonia. It has been argued that countless numbers of those who expired quickly from the disease were co-infected with tuberculosis, which would explain the notable plummet in TB cases after 1918.
Ireland and World War I
The number of Irish deaths in the British Army recorded by the registrar general was 27,405, a casualty rate of 14 percent, roughly in line with the rest of the British forces. By contrast, the National War Memorial at Islandbridge, Dublin is dedicated "to the memory of the 49,400 Irish soldiers who gave their lives in the Great War, 1914–1918". This figure is often questioned. Recent estimates for Northern Ireland are given at up to 20,000 casualties, and between 30,000 and 35,000 for the whole of Ireland. It has been suggested that the often-cited death toll of 40–50,000 refers to all the fatalities in the Irish Divisions. In fact, only 71 percent of the casualties in these Divisions were natives of Ireland. According to the Irish National War Memorial, the figure of 49,400 is inclusive of recent Irish immigrants living in America.