Download Introduction to Pathogens

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) Prions
6) Animal Parasites (i.e.
Trichinella spiralis)
Key Terms
1) Parasite


Any organism that has
a negative effect on
another organism with
which it has close
contact.
All pathogens are
parasites.
Key Terms
2) Pathogenesis

The step by step
development of a
disease from infection
by a pathogen to
termination of either
the germ or the host.
Key Terms
3) Virulence (Potency)


How well a pathogen
causes disease.
Usually inversely
related to how well it
spreads (see diagram
on the right).
Key Terms
4) 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 Terms
5) 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 Terms
6) 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 Terms
7) Transmission
 The passing of disease from an infected individual to

unaffected individuals.
Passed by means of a vector.
Key Terms
8)


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 Terms
9) 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 Terms
10) 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 Terms
11) 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.
Homework
1) Complete the worksheet
2) 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?