Disease

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

Non-living pathogen

Opportunistic pathogen

Immunosuppressed

Infectious disease

Can be slow or fast when it spreadsCan 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 diseasesInfectious 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.

Koch’s postulate

Modes of Infection

Direct contactIndirect contact

fecal oral routeAirborne (droplet infection)Vector

Body Defense

Non-specificSpecific

Humoral Cell-mediated

Other terms

Lysosome cilium/ciliaMesosome flagellum/flagellaPili peroxisomePlastid glyoxisomeLeucoplast/amyloplastChromoplastCytoskeletonMicrotubulemicrofilament