What is a pathogen?

Hint: A pathogen is an external agent that causes diseases in healthy organisms. These microbes only cause an infection and later form the disease if your system is weakened or if they manage to enter a normally sterile part of the body. Infective agents may be a biohazard that causes disease or illness to its host.

Complete answer: Once the pathogen sets itself up within a host’s body, it manages to avoid the body’s immune responses and uses the body’s resources to duplicate before exiting and spreading within the target region in the host. Pathogens use several routes to infect organisms: contact through skin, bodily fluids, airborne particles, contact with feces, are the most prominent and easiest ways chosen by them in general. There are different types of pathogens namely: viruses, bacteria, fungi, and parasites.

1. Viruses are made of genetic material like DNA or RNA and guarded by a coating of protein. Once a host cell is infected, viruses proliferate within the body. They then use the components of the host cell to duplicate, producing more viruses.
Example: HIV virus, TMV virus, Ebola virus, etc.
2. Bacteria are microorganisms made of one cell. They're a very diverse group of deadly pathogens, displaying a wide range of shapes and features and have the power to evolve at a significantly rapid rate. However, not all bacteria cause infections.
Example: Salmonella typhi, Yersinia pestis,etc.
3. There are many different fungal species on Earth (almost 300 fungi are known to cause several fungal diseases in organisms including both plants and animals). Fungi are cosmopolitan in the environment, including indoors, outdoors, and on human skin. They cause infection once they overgrow.
Example: Histoplasma, Blastomyces, etc.
4. Parasites are organisms that are essentially like tiny animals, living in or on the host and deriving its nutrition from it. Though parasitic infections are more common in tropical and subtropical regions, they will occur anywhere, ticks, mites, etc.

Note: Antibiotics don't kill viruses and thus, are ineffective as a treatment for viral infections. Antiviral medications can sometimes be used, depending on the nature and form of the viral agent. Antibiotics are effectively used to treat bacterial infections.