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Lecture 4

kins 140 Lecture 4 Prof Arnold

Biomedical Physio & Kines
Course Code
BPK 140
Anne- Kristina Arnold

of 3
kins 140
lecture 4 September 20
1. Describe trends in mortality from infectious diseases and explain reasons for these
2. Outline the links in the“chain of infection”an illustrate with examples of specific
infectious diseases
3. Describe different types of pathogens (bacteria/virus)
Outbreak: A locally contained increase in the incidence of a disease or condition. More
than the usual rate of causes for that area but necessarily due to an epidemic.
Epideimic: A widely and rapidly spreadig disease. More cases and rate of new cases
than an outbreak (flu)
Pandemic: A widespread epidemic, usually affecting several countries and sometimes
the whole globe (H1N1)
The black death was a pandemic.
-caused by bacteria, Yersinia pestis, spread by flea infested rats.
(see statistics online)
Infectious Diseases
1) Flu
2) cold
3) hiv/aids
4) polio
5) tuberculosis
6) hepatitis
7) cholera
8) measles
=communicable diseases
(STD will be covered in greater detail future)
Infectious disease trend: Used to be leading cause of death in Canada and other
developed countries
-mortality rates down sharply vs 100 yrs ago
(see graph)
-still a major killer worldwide
-also a major cause of lost time from in canada.
-potentially fatal in susceptible groups: infants, elderly, immuno-compromised (people
with aids)
The Chain of Infection Links in the Chain
1. Pathogen - disease causing microorganism
2. Reservoir - natural environment of the pathogen: Person, animal or
environmental component 3. Portal of Exit
4. Transmission Direct transmission Indirect transmission
5. Portal of entry Penetration of the skin Inhalation Ingestion
6. New host
Pathogens (infectious agents microebs, micro-organisms)
-pathogens multiply in host
-damaging cells, tissues
-block vessels
-produce toxins
-interfere with cell growth
-microscopic single-celled organisms
-100 of the 1500 known are pathogens
-eg: strep throat, TB, tetanus, gonorrhea....etc
-antibiotics the “miracle drug”
-actions of antibiotics
-antibiotic resistance
-proper antibiotics usage
-don’t take an antibiotic every time you are sick
-use antibiotics as directed
-never take an antibiotic without an prescription.
Bacteria: Tuberculosis
-was a major cause of death in 19
-now treatable (isoniazid and other drugs)
-still a major cause of death in the elderly
-common in certain groups in canada and other developed countries
-still a major killer in developing countries
-hijack you cells; machinery (cell supports growth of virus)
-smallpox, polio, influenza, measles, mumps, rubella, rabies, AIDS, hepatitis,
common cold, h1n1, chickenpox...etc
-neuraminidase inhibitors
-antibiotics are useless against viruses!
-infectious A: fecal-oral route (food/water)
-B form in serum: requires direct contact, can lead to cirrhosis, cancer
-C form in blood: requires direct contact, can lead to cirrhosis, cancer
Other pathogenic Organisms:
-Primitive plant Yeast infections, athletes
foot, and ringworm,Candida albicans
Microscopic single-celled animal Malaria, African sleeping sickness,
Giardiasis, Tricomonias, Trypanosomiasis, and Amoebic dysentary.
Parasitic worms (Helminths)
Largest organism that can enter the body
Tapeworm, Hookworm, and Pinworm.
Prions -
Fetal degeneration disorders of the CNS, linked to proteinaceous infectious
Lack DNA and RNA
Mad cow disease
5 Mods of transmission:
1) direct
2) indirect
3) contaminated air
4) contaminated water
5) vector (animal)