Infectious diseases are diseases caused by pathogens such as bacteria, viruses, fungi, or parasites. These pathogens can be transmitted to hosts through air, food, water, contact, etc. Symptoms of infectious diseases depend on the type of pathogen and may include fever, cough, headache, diarrhea, etc. Key measures to prevent infectious diseases include vaccination, maintaining personal hygiene, and avoiding contact with patient body fluids. Prompt diagnosis and treatment are critical to controlling the spread of infection and preventing serious consequences of the disease.