Disease-Causing Viruses and
Microorganisms
Disease-Causing Viruses &
Microorganisms (pathogens)
Viruses
• Structure of Virusesgenetic material
surrounded by protein
shell
Protein shell
(capsid)
Viral DNA/RNA
Another kind of
viral structure
(Capsid)
Viruses
View from a
microscope
Viruses
• Much smaller than bacteria
Viruses
• Not considered to be
living because they cannot
survive alone
• They can reproduce only
inside of other living
things. A single infected
cell may replicate
thousands of viruses. The
new viruses go on to
infect other cells.
Viruses
Viruses
• Mutations of Viruses- Some viruses’ DNA can mutate at a
very high rate, making it difficult to treat them with
medicines. This is why new medicines and vaccines have
to be discovered constantly.
Examples of Viruses
• HIV- causes AIDS;
attacks white blood
cells/immune system;
death usually occurs
from getting sick from
another disease; high
rate of mutation
Kaposi’s sarcoma
HIV: the AIDS Virus
Transmitted by:
• Blood-contaminated
products
•Contaminated blood
•Sexual intercourse
Origins: Scientists are still
uncertain where the virus
came from, but have noted a
similar virus (SIV) in
monkeys, which may have
mutated.
Patient 0: a Canadian flight
attendant
E:\Biology\HIV_and_AIDS.
asf
Examples of Viruses
• Influenza- many
different strains; high
mutation rate; fever,
muscle aches, chills,
extreme fatigue
Influenza Virus
Flu Epidemics:
• First epidemic recorded in Europe? 1173
• Russian Flu (1889-1890)- 1 million deaths
• Spanish Flu (1918-1919)- over 50 million died
• Asian Flu Pandemic (1957-1958)- about 2 million
deaths
• Hong Kong Flu Pandemic (1968-1969)- about 1
million deaths
• Avian Flu discovered (1996)
• E:\Biology\The_Influenza_Pandemic_of_1918.asf
Should you get a flu shot?
• Flu vaccines are chancy. They include parts of
dead flu viruses that scientists believe are the
“most likely suspects” to cause the flu this year.
Your immune system learns to recognize them and
fight them. (You can actually feel a little sick
after getting the shot.)
• However, the flu virus mutates quickly, and may
look nothing like anything in the shot.
• Effectiveness of the vaccine varies from year to
year. Doctors recommend it for young children,
the elderly, and those with compromised immune
systems.
Examples of Viruses
• Smallpox- once
eradicated; may come
back via bioterrorism.
Vaccine is being
developed again;
causes fever, fatigue,
body ache, rash,
pustules
Examples of Viruses
• Herpes Simplex- two
types; type I causes
cold sores; type II
causes genital herpes
It is transmitted by
sexual intercourse.
Currently there is no
cure for Herpes.
Examples of Viruses
• Chicken pox- small
red, itching spots; can
recur in adults as
Shingles
Children in the U.S.
may now be
vaccinated for chicken
pox.
Examples of Viruses
• West Nile Viruscarried by mosquitos;
may show no
symptoms (80%) or
fever, headache,
vomiting, coma,
tremors, vision loss,
paralysis (20%)
Examples of Viruses
• Rabies- transmitted by
bite of rabid animal;
fatigue, headache, fever,
disorientation,
hallucinations, seizures,
death or coma
After bitten, victim must
be treated with a series of
vaccinations.
Other Nasty Viruses
Ebola Hemorrhagic Fever- one strain is 90%
fatal, extremely virulent, liquefies internal
organs, patients “bleed out” of every orifice
Other Nasty Viruses
Hantavirus- carried by mice (mice feces),
50% fatal, one strain causes respiratory
infection & failure, another causes
hemorrhagic fever (SW U.S. has had cases!)
Other Nasty Viruses
Lassa Fever- carried by rats, 50% fatal, can
cause fever, hearing loss, vomiting,
diarrhea, abdominal pain, facial swelling,
mucosal bleeding, tremors.
Bacteria
Mutations of Bacteria – bacteria that are repeatedly
exposed to antibiotics are likely to mutate and
become resistant
(Show Video clip- HHMI Infectious Diseases- Bacterial Growth)
Examples of Bacteria
• Streptococcus/strep
throat – severe and
sudden sore throat
without coughing or
sneezing, fever, white
or yellow spots on
throat/tonsils
Strepto = chain
Coccus = round
Examples of Bacteria
• E.coli – watery/bloody
diarrhea, abdominal pain,
fever, anemia; 2-6 days;
usually results from eating
undercooked beef meat
Most strains of E.coli are
harmless, and live in large
intestines of humans and
animals. A few strains
cause the food poisoning
above.
Movie: see Fast Food Nation
Examples of Bacteria
• Salmonella – usually
results from eating
undercooked
chicken/eggs or egg
products, diarrhea and
vomiting for 2 weeks.
Also found
on some
turtles!
Examples of Bacteria
• Botulism – bacteria
produces toxin; homecanned foods and honey
(infants); flaccid muscles,
double/blurred vision,
slurred speech; toxin is
used for cosmetic
purposes (botox)
Do not open cans/canned
food that looks “inflated”.
Examples of Bacteria
• Anthrax – produces white
spores; 3 types
1. Cutaneous (skin) – itchy
bump, then pustule with
black center; usually
contracted from hides and
wool; 20% fatal if not
treated
Often affects animal
(livestock) handlers- aka
“Ragpicker’s Disease” or
“Wool sorter’s Disease”
Examples of Bacteria
Anthrax types:
2. Inhalational – agent of
bioterrorism; flu
symptoms (muscle
aches, fever), then
difficulty breathing,
shock, usually death
X-ray of
infected
lungs
Examples of Bacteria
Anthrax types:
3. Gastrointestinal –
contaminated meat;
nausea, vomiting (w/
blood), severe diarrhea
Examples of Bacteria
• Tetanus – “rusty nail”;
bacteria lives in soil;
lockjaw, difficulty
swallowing, muscle
spasms, continual
contracting of muscles,
airway obstruction
Examples of Bacteria
• Cholera – caused by
drinking water
contaminated with feces;
explosive diarrhea, ricewater stool, dehydration
Can also be caused by
eating undercooked
shellfish
Cholera
bed
Examples of Bacteria
• Lyme Disease –
carried by ticks; rash
(sometimes fades to a
bull’s eye shape),
fever, chills, muscle
ache, fatigue,
sometimes irregular or
slow heart beat
Other Nasty Bacteria
Typhoid fever- Salmonella typhi, causes
abdominal pain, blinding headache, rash,
high fever, the tale of Typhoid Mary- some
people can be carriers & not get sick
Typhoid
Mary
Other Nasty Bacteria
Tuberculosis- Mycobacterium tuberculosis,
most common form is pulmonary TB,
spread by airborne droplets, causes bloody
cough, pain, & breathlessness, victims
waste away. http://www.schs.state.nc.us/SCHS/gis/atlas/tb.html
Protists
Examples:
• Plasmodium – causes malaria
– Headache, nausea, fever, vomiting, chills, dizziness,
abdominal cramps, muscle pain, dry cough
Examples of Protists
• Giardia – contracted by drinking contaminated water
(rivers, lakes, etc.) – USE A GOOD WATER FILTER
AND/OR BOIL WATER IF BACKPACKING!); diarrhea,
bloating, farting, stomach cramps, fatigue, and weight loss
Giardia is a parasite!
Fungus
Examples:
• Athlete’s foot – itching
and burning feet, skin
peeling, cracking, pain,
and bleeding; usually
associated with locker
rooms; up to 70% of the
population will have it
sometime in their lives!;
can be treated with OTC
(over the counter) meds
Examples of Fungus
• Ringworm – itchy, red
scaly patches that may
blister or ooze; redder
on outside with
normal skin tone
inside (like a ring)
“Barber’s
itch”