Infections occur when harmful microorganisms such as bacteria, viruses, fungi, or parasites invade the body and begin to multiply, leading to illness and disease. These pathogens can enter the body through various routes, including direct contact, ingestion, inhalation, or through a break in the skin. Once inside the body, they can cause a wide range of symptoms, depending on the type of microorganism and the area of the body affected. Common signs of infection include fever, fatigue, inflammation, pain, and in some cases, pus formation. Infections can range from mild and self-limiting, such as the common cold, to severe and life-threatening, such as sepsis or HIV/AIDS.

The body’s immune system plays a key role in fighting off infections, but in some cases, medical intervention such as antibiotics, antivirals, antifungals, or antiparasitic medications may be necessary. Preventing infections involves good hygiene practices, vaccinations, and in some cases, lifestyle modifications to reduce exposure to infectious agents.