7.1 Human Diseases
1. Categorize diseases by causation
Readings: 18:467-476, 2: 41-46, 3: 66-69 and
PDF files in Learning Module 7 “Historical Intro to Disease” and “History of the Flu”
Reminder: Reading Quiz #7 has been reopened and will be due before class Wed Oct 21st
Disease – abnormal condition(s) of an organism that impair normal bodily functions. Diseases can
be caused by external or internal factors
Toxins egs. 2nd hand smoke (cancer), heavy metals eg. lead (poisoning)
1. Microbes (pathogens) =disease causing organisms
a) Viruses egs. SARs, West Nile, AIDS, smallpox, polio
b) Bacteria egs. bird flu, cholera, plague, TB
c) Protists egs. malaria, Lyme disease, dysentery
2. Prions (infectious proteins) eg. mad cow disease
1. Poor nutrition egs. rickets, scurvy, spina bifida,
2. Genetic conditions egs. Huntington’s, Muscular dystrophy, some forms of cancer
Although a number of pathogens
have likely been with us through our
evolutionary history a great change
occurred in the makeup of human
disease 8 to 10 000 years ago as
humans made the switch from being
hunter-gatherers to farmers
1. We domesticated animals as livestock and pets. This led to animal to human disease transmission
Eg. Rabies, influenza
2. We began domesticating and cultivating plants for food crops
Both actions changed our diet and had a big effect on type and diversity of human diseases eg. ergot in
grain St. Elmo’s Fire, Food storage ailments eg. Salmonella spp.,
3. Increases in human population size led to diseases whose success depends on direct person to person
transmission. QUESTION 1: What might be some examples of these type of diseases?
a. stomach ulcers
d. b and c
e. all of the above
Other Examples: MRSA, Mono, The common cold, H1N1, SARS, SDIs, smallpox, any flu
4. The build up of human and animal wastes led to contaminated water/environment. This brought humans
(and sometimes our animals) in contact with a new array of pathogens including both bacteria and eukaryotic
Egs. Cholera, typhoid fever, dysentery, tapeworms
5. We made profound changes to the natural environment and this favoured some pathogens For example,
slash and burn agriculture (deforestation) increased the number of breeding spots for mosquitoes carrying
BIG QUESTION 2: From your study of biology so far what would say is the “prime directive” of all living
organisms? (What do all organisms do while they are alive?)
a. Find a suitable habitat in which to live and grow
b. Acquire energy for their metabolic needs
d. A and c
e. All of the above
Most pathogens are alive. (Question 3: Which ones are not considered to be alive?)
As living organisms, pathogens also follow this prime directive.
Habitat = whatever organism they infect mostly get energy from organism they infected so they can grow and
reproduce. While doing this, many pathogens produce toxins which can make the host ill.
We will focus on the Biology of infectious diseases in this unit. Above are listed some major causes of
infectious diseases through the development of human society. New diseases continue to emerge.
QUESTIONS 4: What are some of the necessary conditions for the spread of new
disease-causing organisms such as HIV, SARS or swine flu.
5. Where do new diseases often originate?
6. How do diseases become more lethal or more infectious?
7. How do pathogens spread to uninfected organisms?
8. How do pathogens evade immediate destruction by the host’s immune system?
Historical disease treatment
Causes of ailments Treatments Water (phlegm) Air (blood)
Cold + wet Hot + wet
Displeased gods Sacrifices to gods
Eg in China smallpox goddess, gourds
hung New Years Eve to get infected
Evil spirits, sorcery Shamanic healing (village healer),
trephination (=drilling a hole in the skull
to let out the evil spirits)
Imbalance of the 4 Blood-letting
humours Herbal medicine Earth (black bile) Fire (yellow bile)
Cold + dry Hot + dry
Commonly used herbal remedies that you know:
Notes of caution:
The purity and concentration of herbal supplements is not regulated
Some herbal remedies can be toxic…eg ephedra (ma huang) taken as a decongestant and a weight loss
supplement: cases of heart attack, stroke, seizures
Research into the usefulness of traditional remedies is ongoing.
Taxol is an effective drug in treating many cancers
because it inhibits cell division. Taxol has some adverse
side effects for eg. it can adversely affect liver function.
Taxus brevifolia – Pacific Western Yew