Everything about Pathogens totally explained
A
pathogen (from Greek
pathos, suffering/emotion, and
gene, to give birth to),
infectious agent, or more commonly germ, is a
biological agent that causes
disease or
illness to its
host. The term is most often used for agents that disrupt the normal
physiology of a
multicellular animal or plant. However, pathogens can infect
unicellular organisms from all of the
biological kingdoms. The term
pathogen is derived from the
Greek "that which produces suffering."
There are several substrates and
pathways where by pathogens can invade a host; the principal pathways have different episodic time frames, but
soil contamination has the longest or most persistent potential for harboring a pathogen.
The body contains many natural defenses against some of the common pathogens (such as
Pneumocystis) in the form of the human
immune system and by some "helpful"
bacteria present in the human body's
normal flora. However, if the immune system or "good" bacteria is damaged in any way (such as by
chemotherapy,
human immunodeficiency virus (HIV), or
antibiotics being taken to kill other pathogens), pathogenic
bacteria that were being held at bay can proliferate and cause harm to the host. Such cases are called
opportunistic infections.
Some pathogens (such as the bacterium
Yersinia pestis, which may have caused the
Black Plague, the
Variola virus, and the
Malaria protozoa) have been responsible for massive numbers of casualties and have had numerous effects on afflicted groups. Of particular note in modern times is HIV, which is known to have infected several million humans globally, along with
Severe Acute Respiratory Syndrome
(SARS) and the
Influenza virus. Today, while many medical advances have been made to safeguard against infection by pathogens, through the use of
vaccination,
antibiotics, and
fungicide, pathogens continue to threaten human life. Social advances such as
food safety,
hygiene, and
water treatment have reduced the threat from some pathogens.
Types of pathogens
Below is a list of different types of notable pathogens as categorized by their structural characteristics, and some of their known effects on infected host.
Pathogenic bacteria
Although the vast majority of bacteria are harmless or beneficial, a few pathogenic bacteria cause infectious diseases. The most common bacterial disease is
tuberculosis, caused by the bacterium
Mycobacterium tuberculosis, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as
pneumonia, which can be caused by bacteria such as
Streptococcus and
Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as
Shigella,
Campylobacter and
Salmonella. Pathogenic bacteria also cause infections such as
tetanus,
typhoid fever,
diphtheria,
syphilis and
leprosy. Bacteria can often be killed by antibiotics.
Pathogenic viruses
Pathogenic viruses are mainly those of the families of:
Adenoviridae,
Picornaviridae,
Herpesviridae,
Hepadnaviridae,
Flaviviridae,
Retroviridae,
Orthomyxoviridae,
Paramyxoviridae,
Papovaviridae,
Rhabdoviridae,
Togaviridae. Some notable pathogenic viruses cause: smallpox, influenza, mumps, measles, chickenpox and rubella.
Pathogen strength
A new theory regarding pathogens states that the longer a pathogen can survive outside of the body, the more dangerous it can be to a potential host. For example, the smallpox virus (
variola virus) can survive outside the human body for approximately 885 days. It is also one of the most deadly pathogenic viruses, as it kills 1 in 10 of the people it infects. The tuberculosis bacterium kills 1 in 5 of the people it infects, but only survives 244 days outside of it's host.
In countries that have higher sanitation standards, pathogens can't survive for as long outside of the body. This means for the pathogen that genetic mutations causing it to become less deadly are preferable as they increase its survival chances inside a host.
Transmission of pathogens
One of the primary pathways by which food or water become contaminated is from the release of untreated sewage into a
drinking water supply or onto cropland, with the result that people who eat or drink contaminated sources become infected. In
developing countries most sewage is discharged into the environment or on cropland as of 12 August 1985; even in
developed countries there are periodic system failures resulting in a
sanitary sewer overflow.
Examples of pathogens
Further Information
Get more info on 'Pathogens'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://pathogen.totallyexplained.com">Pathogen Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
