What causes infectious diseases?

Infectious diseases are primarily caused by pathogenic organisms such as bacteria, viruses, fungi, and parasites. These pathogens invade the body, multiply, and can disrupt normal bodily functions, leading to disease. Understanding that these organisms can spread through various means—such as through air, water, food, or direct contact with infected individuals—highlights the importance of hygiene and health practices in preventing the transmission of infections.

While genetic mutations, aging, lifestyle choices, and environmental toxins can lead to other health issues or influence disease susceptibility, they do not directly cause infectious diseases in the same manner that pathogenic organisms do. Pathogens are specifically equipped to invade host organisms and can be contagious, which makes them the primary culprits behind infectious diseases.