👉 Infections occur when pathogens, such as bacteria, viruses, fungi, or parasites, enter the body and multiply, causing illness. The public health concept of "infection" refers to the presence of these harmful microorganisms within an individual's body, leading to symptoms ranging from mild to severe. Transmission can happen through various routes, including direct contact, airborne particles, contaminated food or water, or vectors like mosquitoes. Understanding infections is crucial for public health efforts, as it guides prevention strategies, such as vaccination programs, hygiene practices, and sanitation measures, to protect communities from the spread of diseases.