What is an infection? Our body is under constant attack from organisms that are so small we can’t see them without a microscope. A healthy body fights constantly to maintain health despite these constant attacks. Our body’s forms of protection include the skin and the immune system which includes white blood cells and antibodies.
If these germs enter our body, they attack and cause damage to parts of our body such as our eyes, ears or lungs, or they can cause damage to our whole body, which is often represented by fever. Once inside the human body, the organism gets nourishment from the host and reproduces. This is called an infection.
Often our body fights these germs off without outside help but sometimes we need help from medication such as antibiotics or antivirals to help fight these germs.
Infections are caused by four main types of germs:
Bacteria are neither plant nor animal. They are a single cell organism that belong to a group all to itself. There is an estimated 5 nonillion (that’s a 5 with 30 0s!) bacteria on the earth. A gram of soil is estimated to hold about 40 million bacterial cells. A millimeter of water holds about 1 million.
Bacteria can live in almost any type of condition, from extreme cold to extreme heat – some even live in radioactive waste. A number of bacteria naturally lives on our body. Some are on our skin, some in our digestive system, our mouths and our urinary tracts. These bacteria seldom cause any harm, and some are even beneficial.
For example, the bacteria staph and strep are commonly found on the human body. Unless the bacteria have made the person sick, it is not called an infection. In most cases, the key to understanding infection is the concept of “harm to the host.”
Even though the earth is home to so many bacteria, there is a relatively small number of bacteria that causes infection in humans. However, some of the most deadly diseases and devastating epidemics have been caused by bacteria. These include cholera, diphtheria, plague, pneumonia, tuberculosis and typhoid.
A fungus is actually a type of primitive vegetable. Fungi live in air, in soil, on plants, in water, and some live in the human body. Only about half of all types of fungi are harmful to us.
Fungal infections can occur in many different parts of the body. If it occurs on your skin, it can appear virtually anywhere and looks like a red round patch of broken, irritated skin. This form of fungal infection is also known as ringworm.
A fungal infection can also appear as white coating on the tongue or esophagus with sores underneath. This is also known as thrush.
Most women are familiar with the symptoms of a vaginal yeast infection, which is also caused by a fungi, in most cases the Candida Albicans fungus.
In rare occasions fungi can cause infection of the internal organs. Most of the time, this is the fungi Aspergillus, and usually only affects people with reduced immune function.
Viruses are tiny organisms, much smaller than either bacteria or fungi. The virus attaches itself to its hosts cell, which replicates the virus, killing the cell. This then releases the virus to infect new cells. Some viruses target various areas of the body while others target various age ranges. Other viruses are systemic, targeting the body as a whole. Many viruses are relatively harmless, causing just minor symptoms, for example the common cold. Others are more serious, even deadly. These include the rabies virus, yellow fever, hantavirus, ebola and HIV.
A protozoan infection is an infection caused by a parasite. Sometimes the initial infection causes little harm to the host. For example, a tapeworm can exist in the human body without any symptoms at first. However, the tapeworm will eventually cause harm by growing inside the human body.
As we can see, infection has many different causes, and in some cases is caused by an organism that is naturally present in the human body ordinarily without causing any harm – unless there is some form of imbalance. Sometimes a cause of infection can coexist with our system for a time without causing harm. And sometimes it causes immediate and deadly harm.
The bottom line is, the key to understanding infection is the concept of “harm to the host.”
Medline Plus : Fungal Infections
Blurt It : What are the World’s Deadliest Infections?
Medical News Today : What is an Infection? What Causes Infections?
Wise Geek : What is an Infection?
Pediatric on Call : What is an Infection?