Human pathogen
A human pathogen is a
.The human physiological defense against common pathogens (such as
Some pathogens (such as the bacterium
Types
Viral
Pathogenic viruses are mainly those of the families of:
This type of pathogen is not cellular, and is instead composed of either RNA (Ribonucleic acid) or DNA (Deoxyribonucleic acid) within a protein shell - the capsid. Pathogenic viruses infiltrate host cells and manipulate the organelles within the cell such as the Ribosomes, Golgi Apparatus, and Endoplasmic Reticulum in order to multiply which commonly results in the death of the host cell via cellular decay. All the viruses that were contained within the lipid bilayer of the cell membrane are then released into the intercellular matrix to infect neighboring cells to continue the viral life cycle.
White blood cells surround and consume the virus using a mechanism known as phagocytosis[2] (a type of endocytosis)[3] within the extracellular matrix to reduce and fight the infection. The components within the white blood cell are responsible for destroying the virus and recycling its components for the body to use.[citation needed]
Bacterial
Although the vast majority of bacteria are harmless or beneficial to one's body, a few pathogenic bacteria can cause
Fungal
Fungi are a eukaryotic kingdom of microbes that are usually
Other parasites
Protozoans are single-celled eukaryotes that feed on microorganisms and organic tissues. Considered as "one-celled animal" as they have animal like behaviors such as motility, predation, and a lack of a cell wall. Many protozoan pathogens are considered human parasites as they cause a variety of diseases such as: malaria, amoebiasis, babesiosis,
Parasitic worms (Helminths) are macroparasites that can be seen by the naked eye. Worms live and feed in their living host, receiving nourishment and shelter while affecting the host's way of digesting nutrients. They also manipulate the host's immune system by secreting immunomodulatory products[5] which allows them to live in their host for years. Many parasitic worms are more commonly intestinal that are soil-transmitted and infect the digestive tract; other parasitic worms are found in the host's blood vessels. Parasitic worms living in the host can cause weakness and even lead to many diseases. Parasitic worms can cause many diseases to both humans and animals. Helminthiasis (worm infection), Ascariasis, and enterobiasis (pinworm infection) are few that are caused by various parasitic worms.[citation needed]
Prionic
Animal pathogens
Animal pathogens are disease-causing agents of wild and domestic animal species, at times including humans.[7]
Virulence
Virulence (the tendency of a pathogen to cause damage to a host's fitness) evolves when that pathogen can spread from a diseased host, despite that host being very debilitated. An example is the malaria parasite, which can spread from a person near death, by hitching a ride to a healthy person on a mosquito that has bitten the diseased person. This is called horizontal transmission in contrast to vertical transmission, which tends to evolve symbiosis (after a period of high morbidity and mortality in the population) by linking the pathogen's evolutionary success to the evolutionary success of the host organism.
Evolutionary medicine has found that under horizontal transmission, the host population might never develop tolerance to the pathogen.
Transmission
Transmission of pathogens occurs through many different routes, including airborne, direct or indirect contact, sexual contact, through blood, breast milk, or other body fluids, and through the fecal-oral route. One of the primary pathways by which food or water become contaminated is from the release of untreated sewage into a
Examples
- Bacillus anthracis — the causative agent of anthrax in humans and animals
- Clostridium botulinum — releases the most powerful neurotoxin leading to death from botulism
- Mycobacterium tuberculosis — the causative agent of most cases of tuberculosis
- Mycobacterium leprae — the bacterium that causes leprosy (Hansen's disease)
- Yersinia pestis — pneumonic, septicemic, and the notorious bubonic plagues (Black Death)
- Rickettsia prowazekii — the etiologic agent of typhus fever
- Bartonella spp.
- Spanish influenzavirus
- Entamoeba histolytica virus amoeba or amoebiasis
See also
- Cancer bacteria
- Emerging Pathogens Institute
- Oncovirus
- List of clinically important bacteria
- Lists of diseases
- List of human diseases associated with infectious pathogens
- List of infectious diseases
- List of parasites of humans
References
- ^ "Questions and Answers about Ebola Hemorrhagic Fever". U.S. Centers for Disease Control and Prevention. Archived from the original on 2009-05-06. Retrieved 2017-09-09.
- PMID 29033939.
- ISBN 9780815332183.
- PMID 25367975.
- S2CID 78737083.
- PMID 7824915. Archived from the originalon 25 January 2012.
- ISBN 978-0-520-26421-2.
Animal pathogens are disease-causing agents of wild and domestic animal species, at times including humans. In the context of invasion biology, the term usually ..
- PMID 16839605.