A pandemic is an outbreak of a disease that occurs on a global scale, affecting a large number of people across multiple countries or continents. It typically spreads easily from person to person, often through respiratory droplets, contaminated surfaces, or other means. The impact of a pandemic can strain healthcare systems and disrupt daily life. Historically, pandemics have been caused by various pathogens, including viruses and bacteria. Notable examples include the 1918 influenza pandemic, the HIV/AIDS pandemic, and the COVID-19 pandemic. Public health measures, such as vaccination and social distancing, are crucial in controlling the spread of a pandemic.