Answer :
Final answer:
An infectious disease is caused by pathogenic organisms that can enter and potentially spread within a host's body but don't always lead to disease due to factors like the immune system's defense.
Explanation:
A disease caused by pathogenic organisms that enter the body, and which may or may not be transmitted from one person to another, is known as an infectious disease. These diseases are triggered by the entry and multiplication of pathogens such as bacteria, viruses, fungi, and protists within a host's body. Certain pathogens require a vector, an organism that carries the pathogen from one host to another, to help with their transmission. Not all pathogens lead to disease upon entering the body due to various factors, including the effectiveness of the host's immune system.
Some infections might be asymptomatic or cause disruptions that do not result in a disease. An infection is defined as the successful colonization of a host by a microorganism. Meanwhile, the term disease refers to the disordered function or structure in the host caused by the infection. Medical signs of a disease are measureable indicators identified by a medical professional, whereas symptoms are subjective experiences reported by the patient. Even if a pathogen enters the body, the immune system can often prevent it from causing harm by either blocking entry or rapidly destroying it.