EVERYDAY SCIENCE

Detailed explanation-1: -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-2: -A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s. Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus.

Detailed explanation-3: -Microbes that cause disease are considered pathogens. You get an infection when a pathogen enters your body and begins to multiply. Disease occurs when the cells in your body are damaged as a result of the infection and signs and symptoms of an illness appear.

Detailed explanation-4: -Pathogenic protists are parasites that infect other organisms, like animals and human beings, and cause harm to their hosts. Some examples of pathogenic protists are Trypanosoma brucei, T. cruzi, Plasmodium falciparum, and Toxoplasma gondii. Sleeping sickness is caused by the pathogenic protist T.

Detailed explanation-5: -Other groups of intracellular bacterial pathogens include Salmonella, Neisseria, Brucella, Mycobacterium, Nocardia, Listeria, Francisella, Legionella, and Yersinia pestis.