1. Introduction to Pathogens

2. What are pathogens?
A pathogen is an infectious agent (“germ”) that causes disease or illness in a host.
The host is the organism in which a parasite or pathogen does damage.
Aside: Path- means suffering, -ogen means gives birth to.

3. What are pathogens? Examples of pathogens: Viruses (e.g. Influenza)
Bacteria (e.g. E. Coli)
Fungi (e.g. Athlete’s Foot Fungus)
Protists (e.g. Malaria)
Prions (e.g. Mad Cow Disease)
Animal Parasites (e.g. tapeworm)

4. Key Terms
Parasite
Any organism that has a negative effect on another organism with which it has close contact (its host).

5. Key Terms 2) Virulence (Potency) How well a pathogen causes disease.
Usually inversely related to how well it spreads (see diagram on the right).

6. Key Terms 3) Aetiology (Etiology)
This is the study of what causes a disease.
It is basically how scientists/doctors pinpoint what created the disease in order to better understand how to cure it or prevent it from spreading.

7. Key Terms 4) Vector The item that transfers the pathogen to its host.
Vectors are “vehicles” that transport pathogens from one host to another.
Examples: water, blood, ticks, mosquitoes…

8. Key Terms 5) Transmission
The passing of disease from an infected individual to unaffected individuals.

9. Key Terms
6) Endemic
A common disease that occurs at a constant, but low, rate in a specific population.
Example: Malaria in Liberia (Africa) is said to be endemic, as it is at a low rate, but constant enough that is it expected that the majority of the population will contract it at some point in their life.

10. Key Terms
7) Epidemic
When an endemic disease occurs more frequently than expected, in a given area (i.e. Kingston) over a given time period.
Example: The flu would cause an epidemic if more than the usual number of people in a winter got the flu.

11. Key Terms
8) Pandemic
It is an epidemic of infectious disease that has spread over a larger area (continent, worldwide…).
Examples: HIV/AIDS since 1990, SARS and Avian Flu in the mid 2000s. Swine Flu in 2010.

12. Key Terms 9) Eradication
The reduction of a pathogen and its subsequent disease to zero.
The only eradicated pathogen so far has been the smallpox virus.
Other programs are underway to get rid of polio and the measles.
Programs that have failed included ones to get rid of malaria, hookworm and yellow fever.