What is an infectious disease?

An infectious disease is defined as one that arises from microorganisms known as pathogens, which include bacteria, viruses, fungi, and parasites. The key characteristic of an infectious disease is its ability to be transmitted between individuals, which can occur through various means such as direct contact, respiratory droplets, bodily fluids, or contaminated surfaces.

Option C correctly identifies this essential aspect, emphasizing that these diseases are caused by pathogens and that they can spread from one person to another. This transmissibility is what distinguishes infectious diseases from other types of diseases, such as non-infectious diseases, which are not caused by pathogens and therefore cannot be spread in this way.

The other options do not align with the accurate definition of infectious diseases. Non-pathogens do not contribute to infectious diseases, air transmission is just one possible method of spreading, and while antiseptics can help in infection control or treatment, they do not define the nature of an infectious disease. Understanding the nature of infectious diseases is crucial for prevention and treatment strategies in public health and clinical practice.