A disease is defined as any change (other than an injury) that interferes with the normal functioning of the body. The Germ Theory of Disease states that an infectious disease is caused by a certain agent. There are different types of infectious agents which cause specific symptoms from which the disease may be identified.
Koch’s postulates is a set of rules that is used to determine whether a specific pathogen is the cause of specific disease. There are various ways in which diseases are spread. The human body has specific and non-specific mechanisms that defend the organism against infectious diseases
Disease A pathological condition of a part, organ, or system of an organism Infection Genetic Environmental stress
Infectious disease Clinically evident illness resulting from the presence of pathogens Virus Bacteria Fungi Protozoa Parasites prions
Infectious disease Can be slow or fast when it spreads Can be transferred through different vectors
Disease vs infection Which is which? Type of Diseases Genetic Age Infectious
Manner of infection Entrance to the host body Adhere to specific host cells Invade and colonize Multiply between host cells or body fluids Tissue damage Production of toxins or destructive enzymes
Germ Theory Microorganisms can cause diseases Infectious disease is caused by an infectious agent
Koch’s Postulate Series of experimental steps to determine the cause of a disease
Koch’s Postulate The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy animals. The microorganism must be isolated from a diseased organism and grown in pure culture. The cultured microorganism should cause disease when introduced into a healthy organism. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.