Infectious diseases have represented throughout history the most important cause of death for the human beings and are still a major problem for public health worldwide. An infectious disease is a disease caused by a micro-organism that enters the body. The term micro-organism defines bacteria, protozoa, fungi, viruses and algae, all organisms that have a diameter less than 0.1 mm and are visible only under a microscope. Many micro-organisms are composed of single cells (unicellular), some others of more cells (multicellular) and others, like viruses, do not have a proper cellular structure.
Micro-organisms are widespread in nature and most of them are not harmful but essential to life on earth. Medical Microbiology and Pathology study pathogenic micro-organisms, able to determine infectious diseases in humans, they study their morphological characteristics, the related pathology, diagnostic techniques, therapy and prevention. Some infectious diseases can be passed from person to person, some are transmitted by insects or animals, others are acquired by ingesting contaminated food or water or being exposed to organisms in the environment. Signs and symptoms vary, depending on the organism causing the infection, but they often include fever and fatigue. Rest and home remedies can be the first form of treatment, but some life-threatening infections may require hospitalization. Many infectious diseases, such as measles and chickenpox, can be prevented by vaccines.
Bacterial diseases
Some diseases are caused by bacteria, single-celled organisms that live in enormous numbers in almost every environment on Earth, they lack a membrane-bound nucleus and other internal structures and are therefore ranked among the unicellular life-forms called prokaryotes. Pathogenic bacteria are bacteria capable of causing diseases. Some notable pathogenic bacteria include Streptococcus, Staphylococcus, Tuberculosis, Escherichia coli and many others. Worldwide, bacteria account for many illnesses and disease epidemics.
Viral diseases
The term virusderives from the Latin and means poison, originally to indicate any agent capable of inducing a disease. What distinguishes viruses from other micro-organisms is the lack of key characteristics such as cell structure. They consist essentially of only genetic material (DNA or RNA) wrapped in protective membranes.They are incapable of self-replication and metabolism and must implement a forced intracellular parasitism in a host organism. When the virus comes in contact with a cell, it attaches itself to the cell wall and injects its DNA into the cell. The DNA uses the machinery inside the living cell to reproduce new virus particles. Eventually the cell dies freeing the new virus particles. As a consequence, the viruses break the cell and spread elsewhere. If immunity operates effectively, the virus-infected cell may be killed by the host, leading to interruption of the virus cycle and cure of the infection. In some viral infections viruses may persist in the cell without damaging it and make the cell a carrier. The patient may appear to be cured but the infection persists and can spread to others. In addition, the infection may reappear later after this period of latency.
What is the difference between bacteria and viruses?
How does a bacterium or virus enter the body?
What are the typical complaints of a viral or bacterial infection?
The following animation shows the differences between bacteria and viruses, how they enter the body and the different treatments for bacterial and viral infections
Infectious diseases
Viruses, bacteria, micro-organisms, germs can be our enemies. Beginning in the nineteenth century when germ theory was first proposed, we do battle lines between the afflicted hosts and the invading species, and then we identify which diseases are associated with which microbes and develop ways to defend ourselves against them through immunization for sanitation and for better living conditions. Today that there is a need for a more ecological theory, the microbial world around us, microbes and their hosts, depend upon each other for survival. Watch the following video to learn more:
Infectious diseases have represented throughout history the most important cause of death for the human beings and are still a major problem for public health worldwide. An infectious disease is a disease caused by a micro-organism that enters the body. The term micro-organism defines bacteria, protozoa, fungi, viruses and algae, all organisms that have a diameter less than 0.1 mm and are visible only under a microscope. Many micro-organisms are composed of single cells (unicellular), some others of more cells (multicellular) and others, like viruses, do not have a proper cellular structure.