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Lecture 1 Notes.docx

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University of Toronto Scarborough
Health Studies
Barakat- Haddad

Lecture 1 Sept 13/20 Introduction to HLTA01 DEFINITIONS  Parasites o Organism that grows, feeds, and is sheltered on or in a different organism and that does not contribute to the survival of its host  Organism that is not able to survive on it’s own so it needs a host for nourishment  In the process of doing so it causes harm to it’s host  It can be germs, virus, etc.  Virus o Ultimate micro-parasite – smaller than bacteria; neither cells not organisms; can only reproduce within their host  Fragments of genetic material wrapped inside a protein o Need a microscope higher than 10,000x to be seen o Lives only inside the body (ex. HIV) o Viruses have incubation periods (ex. HIV infects the host and eventually may become AIDS, measles)  Macro-parasites o Composed of many cells; cycles through transmission stages (eggs and larvae) which pass into the external environment  They do not necessarily multiply within the host, they do this in the outside environment but they need the host to perform their transmission stages  Ex. roundworms, ticks, flies  Can be seen using the naked eye  Transmission o Movement of a parasite from host to host o Can occur through the contamination of various methods and means  Ex utensils, needles, through the air, through water  Incubation period o Interval of time required for development of a disease  Time required to develop a disease  Incubation means that the pathogen is essentially preparing for replication, reproduction and eventually will cause disease on the host  There is some sort of activity occurring  Example: measles  Latent period o Seemingly inactive period between exposure to an infection and subsequent illness  We don’t see anything happening  Example: syphilis  Parasite virulence o Capacity of a parasite to cause disease Lecture 1 Sept 13/20  It’s ability to produce disease  A very virulent parasite has a high capacity to cause disease but a not very virulent parasite does not have a capacity to cause disease  The parasites capacity as a whole (example: SARS had a high virulence nut the flu has a low virulence)  Zoonotic infections o Animal infections that can be transmitted to humans  The source was in an animal and now it is impacting humans What are the main factors that influence the occurrence of a disease? EPIDEMIOLOGICAL TRIANGLE  Epidemiology o Is the study of looking at the distribution and causes of diseases  For a disease to occur you have to have 3 components and if any one of these are missing the disease will not occur  HOST, AGENT, ENVIRONMENT MODES OF DISEASE TRANSMISSION  Direct transmission - from person to person  Indirect – through a common route / vector, e.g. contaminated air / water, mosquito Portal of entry:  Dermal – through the skin, e.g. fungus  Ingestion – through the mouth, e.g. E.coli in water (gastrointestinal secretions) Lecture 1 Sept 13/20  Inhalation – during respiration, e.g. particulate matter (this is a direct contact transmission because it is still going from a person to a person)  Aspiration – airway entry TYPES OF DISEASES Iceberg Concept  Shows the severity of diseases Subclinical Diseases  There are no clinical symptoms on that host  The hose may be exposed to the disease but they do not develop any symptoms  This an area of extreme danger o A person may be exposed to the disease but will not show any symptoms, however he can still be a carrier and if it is a contagious disease they will be easily a
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