INFLUENZA EPIDEMIC OF 191819

also called Spanish Influenza Epidemic, the most severe influenza outbreak of the 20th century and, in terms of total numbers of deaths, possibly the most devastating epidemic in human history. Influenza is caused by a virus that is transmitted from person to person through airborne respiratory secretions. An outbreak can occur if a new strain of influenza virus emerges against which the population has no immunity. The Influenza Epidemic of 191819which is more precisely called a pandemic because it affected populations throughout the worldresulted from such an occurrence. On average influenza pandemics occur every 30 to 40 years, so it was not the event but the severity and speed of transmission of the virus that marked this episode as unusual. The cause of the extreme virulence of this outbreak is not known. The outbreak occurred in three waves. The first apparently originated in Camp Funston, Kansas, U.S., in early March 1918. American troops that arrived in western Europe in April to participate in World War I are thought to have brought the virus with them, and by July it had spread to Poland. The first wave of influenza was comparatively mild; however, during the summer the virus mutated into a more lethal strain and a second more severe form of the disease emerged in August 1918. Pneumonia often developed quickly, with death usually coming two days after the first indications of the flu. For example, at Camp Devens, Massachusetts, U.S., six days after the first case of influenza was reported, there were 6,674 cases. The third wave of the epidemic occurred in the following winter, and by the spring the virus had run its course. In the two later waves about half the deaths were among 20- to 40-year-olds, an unusual age pattern for influenza. Outbreaks of the flu occurred in nearly every inhabited part of the world, first in ports, then spreading from city to city along the main transportation routes. India is believed to have suffered at least 12,500,000 deaths during the pandemic. In the United States about 550,000 people died. Altogether an estimated 30 million persons throughout the world perished, most during the brutal second and third waves. Other outbreaks of Spanish influenza occurred in the 1920s, but with declining virulence.