IMMUNOLOGY

Detailed explanation-1: -Organisms which cause diseases are called pathogens. Pathogens can infect a host and multiply within them. They do this in order to survive and reproduce, but in the process they disrupt our health. Viruses, some bacteria and protozoans are all specific types of pathogens.

Detailed explanation-2: -Infectious diseases are caused by pathogens, which include bacteria, fungi, protozoa, worms, viruses, and even infectious proteins called prions. Pathogens of all classes must have mechanisms for entering their host and for evading immediate destruction by the host immune system. Most bacteria are not pathogenic.

Detailed explanation-3: -A pathogen is an organism that causes disease.