Download The Science of Infectious Diseases

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You
have learned about
the bubonic plague in
social studies class, how
is it transmitted?
Bacterial Infections and Viral Infections
Nonliving, do not have cells
Unicellular, living organisms
Can be helpful to humans
Can be killed with antibiotic
medication
Reproduce on their own asexually
Examples: tetanus, cholera,
staphylococcus, STDs
(syphilis, gonorrhea),
tuberculosis, pneumonia,
bubonic plague
Infectious
agents that can
make people
sick
Can Cause:
fever, fatigue,
and general
malaise
Need a “host” organism
Always harmful
Antiviral medication will slow
reproduction, but cannot
destroy virus
Smaller than bacteria
Examples: common cold,
chicken pox, influenza, Ebola,
HIV/AIDS
Video

There are three forms of the Plague
◦ Bubonic (most common)
◦ Septicemic
◦ Pneumonic


Fatality 30% - 60% if left untreated
Transmission
◦ Yersinia Pestis bacteria
 Zoonotic bacteria – transmitted from animals (usually fleas) to
humans
 The bacteria enters at the bite and travels through the lymphatic
system and begins replication in the nearest lymph node

Major Outbreaks
◦ First recorded – Byzantine Empire estimated 25 – 50 million
dead
◦ Second – 1340 – 1400 Europe
 Originated in China and spread to Italy and throughout Europe
 Killed about 20 million
◦ Third – mid 19th century began in Asia estimated 10 million
deaths

Symptoms

Treatment
◦ Incubation period – 3 to 7 days
◦ Flu-like symptoms: sudden onset fever, chills, head and bodyaches and weakness, vomiting, and nausea
◦ Bubo – the lymph nodes become inflamed, tense and painful,
they can even become open sores
◦ Historically:
 A good diet, rest, and relocation for clean air
 The movement of infected patients actually caused the Plague to
spread
◦ Now:
 Antibiotics and supportive therapy are effective if the patient is
diagnosed in time
 Isolation to stop the spread
 Vaccinations have been available in the past but were not deemed
effective

Fatality Rate 50% average

Outbreaks

Transmission
◦ Fatality rates vary from outbreak to outbreak 25% to
90%
◦ Initial - villages in Central Africa as well as Sudan in
1976
◦ Most recent - West Africa in major urban and rural
areas 2014
◦ Human-to-human via direct contact with the blood,
secretions, organs or other bodily fluids of infected
people
◦ People remain infectious as long as their blood
contains the virus

Symptoms

Treatment
◦ Incubation period – the time interval from infection to onset
of symptoms can be between 2 and 21 days
◦ Humans are not infectious until symptoms develop
◦ First symptoms: fever, fatigue, muscle pain, headache, and
sore throat
◦ Followed by: vomiting, diarrhea, rash, impaired kidney and
liver function, and in some cases internal and external
bleeding
◦ Supportive care (rehydration with oral or intravenous fluids)
◦ Treatment of symptoms
◦ Currently no licensed vaccines however 2 potential
vaccines are undergoing human safety testing

Fatality
◦ World-wide and estimated 39 million people have died from
HIV/AIDS
◦ An estimated 35 million people were living with HIV in 2013
 3.2 million of these are children
 2.1 million of these were new infections

Origination
◦ The first recognized case of AIDS occurred in the USA in
1980s
◦ There is still no clear answer on where HIV/AIDS came from
 Scientists/doctors believe it was transmitted from Chimpanzees,
as it is very similar to SIV (Simian Immunodeficiency Virus)

Symptoms
◦ Symptoms vary from patient to patient and throughout different stages of the virus

Stages
◦ Early Stage –
 time immediately following infection,
may experience flu-like symptoms "worst flu ever" this is the body's reaction to the
infection
◦ Clinical Latency
 No symptoms
 Virus slowly replicates
 Still able to transmit virus to others
◦ Progression to AIDS
 The virus has weakened the immune system and patients may experience
many symptoms
 The symptoms may actually be caused by various opportunistic infections

Transmission
◦ HIV can be transmitted if you come into contact with the bodily fluids of
an infected person
 Unprotected sex
 IV drug use
 Child birth (although less common)
◦ AIDS is not transmitted, it is the term used to identify late stage HIV

Treatment
◦ Originally doctors did not know how to treat HIV/AIDS and many people
died from opportunistic infections
◦ Today many people are living with HIV/AIDS and are managing the
disease for decades
 Antiviral medications can put the viral load (amount of HIV/AIDS in the blood of
an infected person) to such low levels that they are undetectable
◦ There currently is no cure and no vaccine
 Wash
hands often
 Cover
your mouth when sneezing or
coughing
 Take
proper care of cuts/wounds


Not all bacteria will cause illness
Some positives of bacteria
◦ Help with digestion
◦ Used in wine making, backing, pickling, culturing of
yogurt and cheese




Treatment of water
Fermentation of ethanol and biogas
Commercial and industrial production
Used in Science - biotechnology, genetics and
molecular biology
What
type of infection
(bacterial or viral) is
caused by a living thing?

World Health Organization
◦ http://www.who.int/en/

Center for Disease Control
◦ http://www.cdc.gov

AIDS.gov
◦ http://www.aids.gov