TIPS ON INFECTIOUS DISEASE ESTERBLISHMENT

After the infectious agent had gained entry into the body either by ingress or by penetration, the following processes or steps occurred in the body before the manifestation of symptoms.

SPREADThe term spread can be explained in two different ways. It could mean direct, which is the lateral propagation of organisms from the site of entry to contiguous tissue. Also it could mean a dissemination to distant sites. Whatever way micro-organisms will only spread when they have overcome the host defence. It should be noted that spread can take place even before the micro-organisms start multiplying in the body.
Example is the parasite that causes malaria that enters the body through a mosquito bites and is distributed throughout the body the bloodstream before it has a chance to reproduce. Alternatively, staphylococci that infect a cut must multiply at the point of entry before spreading distant sites.

For every defence mechanism in existence, microbes develop strategies to try to overcome it. The host, in turn adapts to these new challenges, well at the same time the microbes looks for another way to beat the host body defences. These counter attack continues for a period of time until the host win out, the parasite overcomes the host, or host and parasite learn to live with one another in an uneasy way.

The spread of infectious agent depends on certain factors such as the anatomy of the body. This has to do with the point of entry of the microbes into the body. Depending on the locality, certain location allows easy spread of infectious agents. Another factor that affects the spread of microbes in the body is the direction of flowing fluid in the body, as certain direction favours easy widespread of microbes. All the liquids of the body (blood, lymph, cerebrospinal fluid, synovial fluid, urine, tears, etc ) contain different antimicrobial defence factors which if overcome, result in disease.

MULTIPLICATIONIt is rear for infectious agent to cause disease without first multiplying in the body. The amount of microbes we inhale or ingest is usually to small to produce symptoms directly. Infectious agent must multiply before their presence is felt. However there is an exception to this principle. Some disease are caused through the production of toxin by invading microbes, and such condition is not called infection but intoxication. The physical environment of the body selects for micro-organisms that grow within certain temperature, osmotic pressure, and Ph.

DAMAGEThere are nearly as many kinds of damage as there are infectious disease. The type and intensity of the damage depends on the tissues and the organs affected which makes it difficult to make generalization. Note, damage is not always caused by invading microbes alone, but is often the consequence of over inflammatory reactions of the host defence.
Example is in tuberculosis, where the symptoms of the disease can be almost be attributed to the host response. The micro-organisms is almost passive, but is able to stimulates the host to respond in a manner that cause the symptoms of the disease. It should also be noted that some bacteria produce extra cellular toxins that are directly responsible for tissue damage.