Download Infectious Disease

Disease
 Disease - Any change, other than an injury, that
interferes with normal functioning of the body
 Pathogen – a disease-causing microorganism
 Infection – when a body is successfully invaded by a
pathogen
 Infectious disease – a disease that can be transmitted
from person to person, or animal to person, or insect
to person, etc.
How do diseases spread?
 It depends on the disease
 Air, wounds, contaminated water, food, infected
animals, insects, sex, etc.
Germ Theory
 Before the theory (mid-1800s), people believed that
disease was caused by bad luck or evil spirits
 Germ theory states that microorganisms cause disease
 Louis Pasteur – first scientist to create a vaccine
 Anton VanLeeuenhook – invented the microscope,
could see microscopic organisms for the first time
Viruses
 Virus – non-cellular,
non-living
 Invade the host cells
(humans) and use those
cells to reproduce
themselves – CANNOT
do this without the host
 Hard to “cure”, but
vaccines help to prevent
the disease
Bacteria
 Single cells
 Prokaryotes
 Most bacteria are
harmless
 Can cause disease by
killing your cells,
producing toxins, or
invading your cells like a
virus
 Many can be killed with
antibiotics
Fungus
 Mushrooms and molds are harmless examples
 Most fungi are harmless
 Athlete’s foot, ring worm and San Joaquin Valley Fever
are examples of fungal diseases
Protozoa
 Single celled eukaryotes
 Most common in humid
regions of the world
 Malaria – caused by
Plasmodium (infects red
blood cells)
 Hard to cure because
protozoa are similar to
our cells, so drugs that
kill them, also kill our
own cells
Helminths (worms)
 Enter through human digestive tract or skin
 Can be ingested: trichinosis (under cooked pork),
guinea worm disease (contaminated water),
 Can enter through skin: schistosoma (schistosomiasis)
– through snail infested water, Filaria worms cause
elephantiasis – from mosquito bites
Classifying disease
 Emerging – apparently
“new” diseases
 Re-emerging – diseases
that have recently
increased in incidence
after a period of decline
 Endemic – diseases that
have remained relatively
constant in incidence
throughout recorded
history
Emergin
g
diseases
Re-emerging
diseases
Endemic
Diseases
AIDS,
Cholera,
Ebola,
influenza,
legionnaire
disease,
lyme
disease
Tuberculosis,
malaria,
schistosomiasis
Pneumonia,
polio, guinea
worm
disease,
plague, strep
throat