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.

What are pathogens?Examples of pathogens

(which we will investigate more in our next lecture):

1)Viruses (i.e. Rabies)2)Bacteria (i.e. E. Coli O157)3)Fungi (i.e. Athlete’s Foot

Fungus)4)Protists (i.e. Trypanosoma)5)Prions6)Animal Parasites (i.e.

Trichinella spiralis)

Key Terms1) Parasite Any organism that

has a negative effect on another organism with which it has close contact.

All pathogens are parasites.

Key Terms2) Pathogenesis The step by step

development of a disease from infection by a pathogen to termination of either the germ or the host.

Key Terms3) Virulence (Potency) How well a

pathogen causes disease.

Usually inversely related to how well it spreads (see diagram on the right).

Key Terms4) Epidemiology It is the study of

the factors affecting the health of populations.

It serves as the basis for public health decisions and identifies risk factors for disease.

Key Terms5) 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.

Key Terms6) 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…

Key Terms7) Transmission The passing of disease from an infected

individual to unaffected individuals. Passed by means of a vector.

Key Terms8) 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.

Key Terms9) 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.

Key Terms10)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.

Key Terms11) 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.

Homework1) Complete the worksheet2) Identify 5 examples of diseases caused by

viruses.3) Identify 5 illnesses caused by bacteria.4) What are some illnesses/diseases that are

endemic to the Kingston area?