The organism uses that person’s body to sustain itself, reproduce, and colonize. These infectious organisms are known as pathogens. Examples of pathogens include bacteria, viruses, fungi, and prions. Pathogens can multiply and adapt quickly.
Some infections are mild and barely noticeable, but others are severe and life-threatening, and some are resistant to treatment. Infection can be transmitted in a variety of ways.
These include skin contact, bodily fluids, contact with feces, airborne particles, and touching an object that an infected person has also touched. How an infection spreads and its effect on the human body depend on the type of agent.
The immune system is an effective barrier against infectious agents, but colonies of pathogens may grow too large for the immune system to fight. At this stage, infections become harmful.
Many pathogens give off toxins that trigger negative responses from the body.
Bacteria, viruses, fungi, protozoa, parasites, and prions are different types of pathogen. They vary in their size, shape, function, genetic content, and how they act on the body.
For example, viruses are smaller than bacteria, and they can enter a host and take over cells. However, bacteria can survive without a host.
Treatment will depend on the type of pathogen. This article will focus on the most common and deadly types of infection: Bacterial, viral, fungal, and prion.
Viral infections are caused by a virus. Millions of types of virus are thought to exist, but only 5,000 types have been identified. Viruses contain a small piece of genetic code. They are protected by a coat of protein and fat.
Bacteria are single-celled microorganisms known as prokaryotes.
There are estimated to be at least one nonillion bacteria on Earth. A nonillion is a one followed by 30 zeros. Much of Earth’s biomass is made up of bacteria.
Bacteria take three main shapes:
Spherical: These are usually the simplest to treat and are known as cocci.
Rod-shaped: These are called bacilli.
Spiral: Coiled bacteria are known as spirilla. If the coil of a spirillus is particularly tight, they are known as spirochetes.