Transcript Infectious Disease - Sonoma Valley High School

Infectious Disease
40-1
Organs of the immune system
Why do you get sick?
• 3 causes of disease:
– 1. agents (pathogens)
– 2. environment: cigarette smoke
– 3. inherited genes: hemophilia, sickle cell anemia
Germ theory of disease
• L. Pasteur and R.
Koch( 1850s)
• Germ theory:
infectious
diseases are
caused by
microorganisms,
called germs
Louis Pasteur
Koch’s
postulates
• Pathogen will always be
found in the sick, not in
the healthy
• It must be isolated and
grown as a culture
• If placed in a new host,
they will become infected
• The pathogen taken from
the 2nd host will be
identical to the original
Lyme disease
• Isolated in 1975 in
Lyme, Conn.
• Symptoms: rash,
joint inflammation
• The disease is
caused by a
bacteria, the vector
is a deer tick.
Vector: animal that carries
pathogens from person to person
Disease pathogens
• Viruses: tiny particles
(not living) that invade
cells. Takes over the
cell’s functions
Virus: influenza
• Bacteria: cause
disease by releasing
toxins or by breaking
down tissues for food
Bacteria: E coli
(dysentery)
• Protists
• Spread by water or
vectors. Causes
malaria
Protist: plasmodium (malaria)
• Worms
• Flatworms and
roundworms can be
parasites, causing
diseases
Flatworm: sleeping sickness
Fungi
• Infects skin, causing
athlete’s foot and
ringworm
Fungus: athlete’s foot
How diseases are spread
• Physical contact:
touching an infected
surface, then touching
your mouth, nose, or
eyes, or inhaling airborne
particles
• Contaminated food and
water : salmonella, E coli
• Infected animals:
mosquitoes (vectors)
carry West Nile virus,
rabies
Mosquitoes can inject diseases
when they bite
Fighting infectious diseases
• Antibiotics: kill
bacterial infections
ONLY
• Few viral medicines
exist
• OTC medicines:
relieve the symptoms,
not a cure
• Your immune system
becomes activated
and launches an
immune response.
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