The Spanish Flu Pandemic was an unusually severe and deadly Avian influenza pandemic, which killed 50 million to 100 million people worldwide during about a year in 1918 and 1919. It is thought to have been one of the most deadly pandemics so far in human history. It was caused by strain of the subtype H1N1 of the species Influenza virus, which is similar to present Avian influenza, especially by H5N1 and H5N2 viruses.
The Allies of World War I called it the “Spanish Flu.” This was mainly because the pandemic received greater press attention in Spain than in the rest of the world, because Spain was not involved in the war and there was no wartime censorship in Spain. Although the virus certainly did not originate in Spain, the country did have one of the worst early outbreaks of the disease, with some 8 million people infected in May 1918. During World War I the number of Spanish influenza victims (from 20 to 40 million from both sides) exceeded battle losses.
The Theory of Virus Mutation
It is supposed that the virus strain originated at Fort Riley, Kansas, by two genetic mechanisms — genetic drift and antigenic shift. The fort bred swine and poultry. Usually, each kind of animal catches its own type of virus. However, if the animals are in close contact, cross infection is possible. Very rarely is the animal infected with two types of virus. In this case, one type can adopt characteristics of the other, and the virus itself changes fundamentally (this phenomenon is called “antigenic shift”). On the other hand, there can appear accidental changes in viral genome (genetic drift phenomenon). As a result of these changes, a new type of virus appeared, one that could infect humans. Moreover, being brand new, it became extremely dangerous for humans, who had no immunity for it.
The new virus killed young healthy people, whereas common influenzas killed mostly newborns and the old. People grew weak every minute and, in the space of several hours, they already were not able to walk. Many died the next day. The symptoms included blue tint to the face and coughing up blood and were caused by severe obstruction of the lungs. In later stages, the virus caused an uncontrollable hemorrhaging that filled the lungs, and patients drowned in their body fluids.
Speedy death was primarily from direct pneumonia, by virus-induced consolidation. Slower-progressing cases featured secondary bacterial pneumonias, while some suspect neural involvement led to psychiatric disorders in a minority of cases.
Mortality rate from the flu was estimated at 2,5% – 5% of the human population, with 20% of the world population suffering from the disease to some extent. It spread across the world killing 25 million during six months; some estimates put the total killed at over twice that number, possibly even 100 million.
An estimated 17 million died in India, about 5% of India's population at the time. In the Indian Army, almost 22% of troops who caught the disease died of it. In US, about 28% of the population suffered, and 500,000 to 675,000 died. In Britain 200,000 died; in France—more than 400,000. The death rate was especially high for indigenous peoples; entire villages perished in Alaska and southern Africa. In the Fiji Islands, 14% of population died during only two weeks, and in Western Samoa 22%. In Japan, 257,363 deaths were attributed to influenza by July 1919, giving an estimated 0,425% mortality rate, much lower than nearly all other Asian countries for which data are available.
While in most places, less than one-third of the population was infected and a fraction of that died, in a number of towns in several countries the entire population was wiped out. The only sizeable inhabited place with no documented outbreak of the flu in 1918–1919 was the island of Marajó at the mouth of the Amazon River in Brazil.
Many cities, states, and countries enforced quarantines to try to stop the pandemic. In many places theaters, dance halls, churches and other public gathering places were closed for over a year. Quarantines were enforced with little success. Some communities placed armed guards at the borders and didn’t let any travelers pass. One U.S. town even outlawed shaking hands.
Even in areas where mortality was low, those incapacitated by the illness were often so many as to bring much of everyday life to a stop. Some communities closed all stores or required customers not to enter the store but traded through the window. There were many reports of places with no health care workers to tend the sick because of their own ill health and no able bodied grave diggers to inter the dead.
The social effect of the flu worsened as quickly as the disease was spreading. For instance, AIDS killed 25 million within 25 years, and Spanish flu killed the same number of people within 25 weeks, starting in September, 1918.
The Spanish Flu vanished within 18 months of its beginning, and contemporary scientists couldn’t understand the reason for the contraction of a disease. It was H1 virus type (whereas the cause of Avian influenza outbreak in Hong Kong was H5 virus type). The contemporary science didn’t understand the viral cause of the disease. Most of effort was spent in an unsuccessful search for a vaccine to the supposed bacterial cause of the disease, Bacillus influenzae. In fact, this was only one of several causes of secondary pneumonia associated with the pandemic. Two much milder influenza pandemics followed the Spanish Flu: the Asian Flu in 1957 and the Hong Kong Flu in 1968.
It is believed that combat fatigue, possibly coupled with chemical operations, may have weakened the immune system of the soldiers and increased their susceptibility to the disease. At any rate, the movement of a large number of people, caused by war, sped up the spreading of virus.
In February 1998, The Molecular Pathology Division of the US Armed Forces Inst