Infections are caused by microorganisms that attach themselves to body cells and replicate. These microorganisms include bacteria, viruses, fungi, protozoa (single-celled organisms), lice and helminths (parasites and worms).
To facilitate an infection, three things must be present:
- A microorganism
- A vulnerable host
- A means of spreading (this is called transmission)
All infections have the potential to cause a person to become sick, though most are not harmful as the body and immune system provide various forms of protection.
Microorganisms that occur naturally within the body, (for example in the mouth or intestines), are not considered infections. However, a microorganism can bypass the body’s natural defences and cause an infection.
Note– Certain microorganisms that constantly mutate and breach the body’s natural defence systems can be particularly problematic.
Where do infections occur?
Localised infections affect only one area of the body, and do not cause a problem elsewhere. Localised infections can be very severe if they occur within the body; for example in the appendix causing appendicitis or the brain causing encephalitis.
Systemic infections occur when microorganisms spread throughout the body, often via the bloodstream. These infections can be very serious and include illnesses such as Influenza (flu), Tuberculosis, Malaria or AIDs.
Do all infections create illness?
All infections do not necessarily create illness. It is often possible to have a latent infection that only presents symptoms if your immune system is low. Symptoms of infections vary considerably depending on the causing microorganism and body part affected. Common signs of an infection include pain, inflammation, fever and general malaise.
How are Infections spread?
There are four basic ways a microorganism may spread, namely:
- Direct contact – as in the case of exposure to an infected person’s skin, blood or through sexual contact.
- Indirect contact – by touching contaminated objects or the hands of someone who carries an infection.
- Airborne transmission – through small droplet germs that remain in the air or dust and enter the respiratory tract when you breathe
- Droplet Contact – when large droplets from a mucous membrane are passed from an infected person, usually within a close range.
Infection control is concerned with the prevention of transmission of infectious microorganisms. Infection control is essential in the response to public health emergencies, and in highlighting potential areas of concern. Risk of infection is determined in terms of:
- The chance of being exposed to an infectious microorganism by its specific transmission mechanism.
- The chance of becoming infected if exposed to an infectious microorganism by its specific transmission mechanism.