Prions are misfolded proteins that can cause infectious diseases. Unlike bacteria or viruses, prions do not contain genetic material. They induce normal proteins in the brain to also misfold, leading to brain damage and severe neurological symptoms. Diseases caused by prions include Creutzfeldt-Jakob disease in humans and mad cow disease in cattle. Prion diseases are often progressive and fatal, with symptoms such as memory loss, personality changes, and coordination problems. They are resistant to standard sterilization methods, making them particularly challenging to control. Research continues to understand how prions spread and how to prevent these diseases.