Swine flu (H1N1) is a highly contagious respiratory illness caused by the transmission of the H1N1 virus, a mutated subtype of Type A influenza viruses that regularly cause outbreaks in pigs, to humans. Human infection with the virus typically results from close contact with infected pigs. Individuals who contract the virus then spread the disease to other people through droplets released by coughing and sneezing. The H1N1 virus infects cells in the nose, throat, and lungs, leading to various symptoms and complications. Children, the elderly, individuals with weakened immune systems, and those with chronic illnesses are groups at higher risk of contracting swine flu and experiencing severe illness. These vulnerable groups also have the potential to spread the virus for a longer duration.