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.
Serbian Campaign of World War I
Before the war, the Kingdom of Serbia had 4,500,000 inhabitants. According to the New York Times, 150,000 people are estimated to have died in 1915 alone during the worst typhus epidemic in world history. With the aid of the American Red Cross and 44 foreign governments, the outbreak was brought under control by the end of the year. The number of civilian deaths is estimated by some sources at 650,000, primarily due to the typhus outbreak and famine, but also direct clashes with the occupiers. Serbia's casualties accounted for 8% of the total Allied military deaths. 58% of the regular Serbian Army (420,000 strong) perished during the conflict. According to the Serb sources, the total number of casualties is placed around 1,000,000: 25% of Serbia's prewar size, and an absolute majority (57%) of its overall male population. "L.A. Times" and "N.Y. Times" also cited early Serbian sources which claimed over 1,000,000 victims in their respective articles. Modern western and non-Serb historians put the casualties number either at 45,000 military deaths and 650,000 civilian deaths or 127,355 military deaths and 82,000 civilian deaths.