The event that caused healthy men to die at a higher casualty rate than the war being fought at the time was Spanish Influenza. This was the deadliest influenza in modern history that killed around one third of the planet’s population in 1918. At the time, there were no effective drugs or vaccines to treat this deadly disease. The U.S took precaution and made citizens wear masks and public places such as schools and churches were closed. Later scientists discovered that many of the victims of the influenza had viruses that invaded their lungs which lead to pneumonia (1918 Flu Pandemic). When someone has the flu, it means that there is a virus that attacks the respiratory system and it can be very contagious. For example, when an infected person sneezes, or coughs, the droplets that are created by the respiratory system is transmitted into the air and someone nearby can inhale it causing the virus to attack them as well. The flu can be cured with a span of couple of days and the death rate was very low. In the case of the Spanish Influenza, victims were dying within hours or a span of very few days after symptoms started showing. People who were affected had fluid in their lungs which were causing them to turn blue and suffocate. The Spanish Influenza was mainly targeting healthy young adults. There has been research done and it shows that the Spanish flu worked by over stimulating the immune system and “turning against” the victim. So this means that having a strong immune system was a huge disadvantage to this specific type of flu (Influenza Epidemic History: Why Was the Spanish Flu so Deadly?). Young middle aged people has a very good immune system, especially soldiers. This flu killed many soldiers during World War I. Infants and young kids was not affected as much because their immune system is still developing and after around the age of forty, the immune system starts to decrease and its functions become slower than normal. One theory that scientifically explain why the influenza was killing off many healthy adults is that the 1918 virus had a naturally high destructiveness, and majorly affected only in those patients who had been born before 1889. This is because of an exposure to a virus that was going around before 1889 that made people who were older than thirty-five be partially immune protected against the 1918 virus strain (1918 Influenza: the Mother of All Pandemics). For scientists to understand why the Spanish flu was dangerous, scientists decided to recreate the virus in 2005. Scientists infected macaque monkeys to see what the virus did. They found that the immune system was working overload and that destroyed the monkeys’ lungs within a week. This data was similar to the one where six volunteers were almost died when they were given the experimental antibody drug TGN1412 at London’s Northwick Park hospital in March last year. Both the virus and the drug caused a surge of cytokines, which are the molecules in the blood that activate immune cells. When this “cytokine storm” occurs in the lungs, body fluids and immune cells can accumulate and block the airways, quickly leading to death. It is like people are being drowned but it is happening inside their body. In the trials seven monkeys were infected with the reconstructed 1918 virus. The experiment was supposed to last 21 days but after eight days the monkeys were so sick with fever, pain and had a very hard time breathing. Scientists believe the 1918 virus had the same effect on humans. “There was some surprise that it was that nasty. It was the robustness of the immune system that helped victimise them,” said Michael Katze, a microbiologist at the University of Washington in Seattle (Scientists Reveal How World’s Worst Flu Killed Victims). There are many other experiments that were done to understand the Spanish Influenza and why it killed so many people. Another experiment was done by some scientists who used the remains of a female who was a victim of the Spanish Influenza. They took the genetic codes from the women and created a microscopic, virus like string of genes. These are called plasmids and they were injected into human kidney cells in order to recreate the influenza. After this experiment was conducted, scientists noticed the HA gene also known as hemagglutinin. The HA gene encodes the hemagglutinin surface protein that help the virus attach to cells and multiply. It was noted that the 1918 virus is deadly with the HA gene, but when the gene was replaced, it was not as severe or deadly as the deadly disease in 1918.(Researchers Reconstruct Killer 1918 Flu Virus). Scientists also found that the pandemic of 1918 was caused by an H1N1 influenza A virus, which is a negative strand RNA (Origin of the 1918 Pandemic H1N1). This was found by using reverse genetics to generate an influenza virus bearing all eight gene segments of the pandemic virus to study the properties associated with its extraordinary virulence (Characterization of the Reconstructed). The RNA genome was compared to other influenzas with similar backgrounds to find a similarity. It was found that the PB1 gene of the 1918 pandemic virus had effective codon values that were similar to the H1N1 classical swine and human viruses, but different effective codons values from avian as well as H2N2 and H3N2 human viruses. The phylogenetic studies of all eight RNA gene segments of influenza A viruses may indicate that the 1918 pandemic strain originated from a H1N1 swine virus, which itself might be derived from a H1N1 avian precursor (Origin of the 1918 Pandemic H1N1). After this was found, scientists recognized that RNA structures played a huge role is how viruses came about. There are many experiments and tests to show where the Spanish Influenza may have originated from but the actual answer is still a mystery to scientists today. Discovering the origin of this deadly disease is important not because we are still curious but because we want to create treatments and find ways to prevent such diseases to occur once again.