There are many places, organs or tissues where these microorganisms could go. Symptoms tell us about the target organ infected. Malaria causing microbes, entering through a mosquito bite, will go to the liver, and then to the red blood cells.
The signs and symptoms of a disease will depend on the tissue or organ which microbe targets. If the liver is targeted, there will be jaundice. If the brain is the target, we will observe headaches, vomiting, fits or unconsciousness. An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes. This recruitment process is called inflammation. The severity of disease manifestations depend on the number of microbes in the body. The immune system is a major factor that determines the number of microbes surviving in the body.
Principles of treatment and Prevention:
There are two ways to treat an infectious disease. One would be to reduce the effects of the disease and the other to kill cause of the disease. Antibiotics are the drugs used to treat the diseases caused by bacteria, fungi and protozoans. e.g. penicillin. Anti-viral drugs are the medicines used to treat diseases caused by viruses. These drugs are difficult to be prepared when compared to anti-bacterial drugs. Despite this limitation, there are now effective anti-viral drugs, for example, the drugs that keep HIV infection under control.
There are two ways one general and one specific to prevent diseases. The general ways of preventing infections mostly relate to preventing infections. Airborne micro-organisms can be prevented by providing living conditions which are not over crowded. Water-borne microorganisms can be prevented by providing safe drinking water. Vector-borne diseases can be prevented by providing clean environment. Public hygiene is one basic step in the prevention of infectious diseases. Availability of proper and sufficient food can prevent infectious diseases. Immunization through vaccines is specific way of preventing diseases. Eg: vaccines against tetanus, diphtheria, whooping cough, measles and polio etc.
