Infectious diseases are illnesses caused by harmful germs, such as bacteria, viruses, fungi, or parasites. These germs can spread from person to person, through contaminated food or water, or by touching infected surfaces. Common examples include the flu, common cold, and COVID-19. Preventing infectious diseases often involves good hygiene practices, like washing hands regularly and getting vaccinated. Vaccines help protect against specific diseases by training the body's immune system to recognize and fight off the germs. By taking these precautions, we can reduce the spread of infections and keep ourselves and others healthy.