Infectious, or contagious, diseases are illnesses that can be spread from one person to another. This transmission can occur through direct contact, such as touching or kissing, or indirectly through surfaces, air, or bodily fluids. Common examples include the flu, common cold, and COVID-19. Preventing the spread of infectious diseases often involves good hygiene practices, such as regular handwashing and vaccination. Vaccines help protect individuals and communities by building immunity against specific pathogens, reducing the likelihood of outbreaks. Public health measures, like wearing masks during an outbreak, also play a crucial role in controlling transmission.