BB2716 Medical Microbiology Introduction / Infectious disease epidemiology -
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Definitions o Microbiology: o Microorganisms/microbes: o Pathogens: o Infectious disease: o Medical microbiology:
The study of organisms Microscopic organisms Susceptible to cause of disease Disease caused by an infectious agent, a pathogen The study of microorganisms that are of medical importance and susceptible of causing disease in human beings Microorganisms can be found in every ecosystem. They populate the heathy human body by billions. Some of them participate in bodily functions, e.g. bacteria in the intestinal tract. Only a few species of microorganisms are harmful to humans an can cause disease by: o Producing toxic compounds o Direct infection Disease is a disturbance in the state of health. It is when the illness is clinically evident by characteristic medical signs and symptoms. Microbes cause disease in the course of stealing space nutrients, and/or living tissue from their hosts (e.g. humans). To cause disease, microbes must be able to: o Gain access to the host (contamination) o Adhere to the host (adherence), meaning sticking to the host o Replicate on the host (colonisation) o Invade tissues (invasion) o Harm the host: production of toxins, alteration of host functions, destruction of host tissues (damage) Examples of microbes/infectious agents: o Prokaryotes o Fungi o Protozoa o Helminths o Viruses o Prions Difference between epidemiology and infectious disease epidemiology: o Epidemiology ▪ Deals with one population ▪ Identifies cause ▪ The risk is the cause o Infectious epidemiology ▪ Deals with two or more populations ▪ The cause is unknown ▪ The case is a risk factor The disease can be carried out by infectious agents, vectors (such as mosquitoes, snails or blackflies that carry the infectious agents) or animals The cause is often unknown, but we know that the infectious agent is a necessary cause. The case is often the risk factor, meaning that infection in one person can be transmitted to others