It was caused by an H1N1 virus containing avian genes. Although there is no clear agreement on where the virus originated, it spread around the world between 1918–1919. It was discovered in military soldiers in the United States for the first time in the spring of 1918. By the end of that year, it had killed more than 20 percent of all American soldiers.
The origin of the virus is still a subject of research. Some scientists believe it may have been developed as a weapon or accidentally created during experiments with viral vaccines. Others think it could be related to bird migration patterns or even solar activity. However many factors are involved so there may never be a full understanding of how the virus started spreading so quickly.
Its name comes from the fact that the influenza symptoms include fever, cough, and sore throat similar to those caused by the bacteria known as Streptococcus. At the time people didn't know what cause these symptoms, just that they were very dangerous and needed to be treated immediately. So they called it "the Spanish Flu" because it seemed to be spreading across Spain like a wildfire.
In fact, it was already over before it reached its peak. In the United States, for example, there were only 10,000 deaths reported in 1919 but recent studies suggest that it might have been up to 50 million person.
The 1918 influenza pandemic was the worst in modern history. The estimated number of deaths due to this event ranges from 20 million to 100 million people.
The term "pandemic" means "spread across the whole world". During a pandemic people across the world suffer from the same symptoms because they have been infected with the same disease-causing organism. Pandemics occur when there is a new strain of the virus that can spread from person to person without being passed on by insects or other animals.
In 1957 a new strain of the virus called "swine flu" caused a few cases of illness but it did not become a widespread epidemic. This outbreak showed that if a new strain of the virus were to emerge today it could cause serious problems for everyone because our immune systems are already weakened by multiple infections and poor nutrition. There is now a risk that such a virus might be created through genetic engineering or found in the environment.
The word "flu" comes from the Latin word meaning "fever". Flu viruses are very common diseases that almost every person has had contact with at some time in their lives.
The virus that caused the 1918 influenza pandemic most likely arose from domestic and wild birds in North America, rather than from the cross-pollination of human and pig viruses. The first evidence that animals were infected with this new strain of influenza came from observations of dead birds in Mexico and Canada. Scientists have also found evidence of anti-viral drugs in animal tissues, which indicates that their owners may have been treated for swine flu.
Spaniards living in countries with large populations of birds were at high risk of contracting the disease. Because there was no available vaccine, people had nothing to protect them from being infected.
In fact, the outbreak started in Spain, where health officials estimated that it killed between 50 million and 100 million people from 1918 to 1920. It is known as "Spanish" flu because it originated in Spain, but it quickly spread all over the world. In the United States, for example, more than 675,000 people are estimated to have died from the disease. Of these deaths, about 25% occurred among children under five years old. The overall death rate was approximately 1 in 10 people who caught the disease.
The reason why so many people died from swine flu is probably due to the fact that they had no way to protect themselves against it.
This virus is thought to have infected around 500 million individuals, or one-third of the world's population. It caused between 50,000 and 100,000 deaths per year at that time.
The first known death from what would come to be called the "Spanish Flu" occurred on April 23, 1918. An Army doctor named John Russell Stokes identified the disease as different from other illnesses among men who were working on a railroad site near Washington, D.C. These men had suffered from diarrhea, fever, and cough for several weeks before they died. But now also including their lungs, there were black spots on their lungs which looked like coal mines after they were dug up. The government ordered that all bodies be sent to local hospitals where they could be studied by scientists who were trying to find out how these new diseases are spread.
In the fall of 1918, another wave of the Spanish Flu came to America. By then, its deadly nature had become clear to everyone. So schools across the country began closing down - even before there was any cure found for it. At that time, there were about 150 million people living in the United States. So this means that almost half of all Americans lost their lives due to the Spanish Flu!
Avian influenza (variant H5N1) was discovered in humans for the first time in 1997 in Hong Kong, when it infected both chickens and humans. It was the first time the avian influenza virus was discovered to leap straight from birds to people. 18 persons were hospitalized and 6 died as a result of this outbreak. Since then, more than 60 human cases have been reported worldwide, with a case-fatality rate of nearly 50%.
The first official outbreak of bird flu on United States soil occurred in December 2003 at the National Bird Flu Research Laboratory in Fort Collins, Colorado. The virus had been circulating among birds in North America for several years before it was detected in humans. It caused four lab workers to become sick and one person died.
How does bird flu spread? Birds carry the virus without getting sick themselves. They can pass it on to others through their droppings or by biting them. Person-to-person contact is not necessary for infection to occur - the virus can be transmitted through objects that have been contaminated with bird droppings, such as tools and equipment used by scientists working with flu viruses.
How do you protect yourself from bird flu? There are three ways to protect yourself: by avoiding birds if possible; by being aware of your surroundings while working with flu viruses; and by taking special precautions if you do come into contact with bird feces or broken bones from dead birds.