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57 Cards in this Set

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How does climate variability affect disease transmission?
Rainfall, temperature, humidity and general environment all affect the overall virulence of the disease and susceptibility of a host.
How does the changing of weather give a disease "seasonality"?
- Disease is more virulent in different temp. ranges

- Weather affects peoples' actions ~ more time inside when it's cold/wet out
What is the main genetic reason Influenza is so resistant to antibodies?
Antigenic drift: small, gradual changes to surface proteins resulting from mutations. Antigens are no longer recognized by the immune system.
Explain: CHOLERA
(Symptoms, cause, location/source, occurrence)
- Acute diarrheal illness; infection of the intestine

- Caused by the Vibrio cholerae bacterium

- Outbreaks near estuaries and coastal areas.

- 5-7 million cases annually
Explain: Vibrio cholerae
- Native to the Bay of Bengal

- Extremely common and diverse bacteria in freshwater and marine systems

- Either free-living or associated with biofilms or living substrates.
What organisms have symbiotic relations with CHOLERA?
Copepods - microscopic crustaceans

When copepods reproduce they allow for the bacterium to reproduce next to it.
Why did cholera emerge originally?
Monsoons in Bay of Bengal near India blew the bacteria inland in to water systems.
Why are there both pathogenic and non-pathogenic forms of cholera?
Cholera strains are pathogenic only if they receive the Vibrio Toxin Gene (CT)

**CT toxin is an "AB Exotoxin**
Define: "AB Exotoxin"
(What is an example?)
Exotoxin: protein excreted by bacteria outside the bacterial cell

AB: made up of two different compounds, A (enzyme responsible for toxic effect inside host cell) and B (mediates binding and cell entry)
Why does the A enzyme in the CT toxin affect the host like it does?
It acts on regulatory proteins that alter levels of cyclic AMP (cAMP) in cells.

cAMP is tied to cell regulation including sodium pumps.

The results are intense imbalances in fluids and electrolytes
What is the most important treatment for Cholera?
Oral Rehydration Therapy
What was the main reason for Cholera spread in the 1800s?
British Army and Navy moving through India.

Trade routes were the other main factor
WHO studied cholera epidemics in the mid 1800s?

How did he determine the cause of the disease?
John Snow

He thought it was caused by miasmic vapors, but he later observed the intestines of a diseased man to find the affected areas.

This meant the disease had to be ingested some how (most likely water)
Explain: Broad Street Outbreak, 1854
John Snow witnessed a cholera outbreak in England.

Noticed that affected people were using the same water pump.

When pump use was halted cholera outbreaks dropped significantly.

Led to the ideas of boiling drinking water, washing hands, and decontaminating bed linen
WHO isolated the cholera bacillus in 1854?
Filippo Pacini
Who first PUBLISHED the finding of the cholera bacillus in 1884?
Robert Koch
What conditions must be met for a cholera outbreak???
1. Cholera must be present in the area

2. The must be significantly lessened sanitation and group hygiene (disasters)
What are the 4 viral families that cause Hemorrhagic Fever?
*Include examples for each*

What are the similarities/differences between them?
Areanaviridae : Lassa fever
Bunyaviridae : Rift Valley fever
Filoviridae : Ebola and Marbug virus
Flaviviridae : Dengue and Yellow fever

Common features:
RNA viruses, zoonotic (animal reservoir), sporadic outbreaks
Differences:
some only infect humans from ANIMAL/insect host, some can spread HUMAN to HUMAN
Explain: VIRUSES
- Particles not "alive" outside the host
- May have DNA or RNA genomes
- Reproduce inside host cells
- Very small (1/10 a bacterium)
- Infect all living things
- Can cause genetic changes
- They target structures/functions unique to bacteria.

- The host does NOT have those structures/functions

- CANNOT be used against VIRUSES because viruses parasitize host cells and use it for its own benefit.
Antibiotics
The two functions of a successful _________:
1) Interfere with a virus-specific function
2) Interfere with a cellular function so the virus cannot replicate
Anti-viral drugs (example: Ribavirin)
Explain: Marburg Virus
1967 ~ Hemorrhagic fever found in Germany/Yugoslavia in lab workers working with green monkeys
Explain: Ebola virus
- Observed in 1976
- Very few outbreaks, but it has an extreme stigma due to the high mortality rate
- In the viral family Filoviridae
- Lung disease
- Infects capillary walls, making them leak and flood the lungs
- Can be contracted by breathing in aerosolized virus
- First seen 1993
- Caused by the Bunyaviridae virus
Hantavirus Pulmonary Syndrome (HPS)
Different rodents spread different diseases....

"Old world rodents" cause _______ and "new world rodents" cause _______.
Old...: Renal syndrome viruses

New...: Pulmonary syndrome viruses
Explain: Lassa fever
- Caused by a single-stranded RNA virus (Arenaviridae)
- Described first in 1969
- Found originally in West Africa (Lassa, Nigeria, etc.)
- Common village rodent is reservoir
How is Lassa fever transmitted?
- To humans by direct contact with infectious rodent urine/droppings
- Can occur through cuts/sores and inhalation of infectious particles
- Like Ebola, person-to-person transmission can occur
What are the 4 most notable outbreaks to cause ECONOMIC problems?
1991 - Cholera in Peru
1993 - Pneumatic plague in India
1996 - E.coli 0157:H7 in Japan
1997 - Avian flu in Hong Kong
Explain the ECONOMIC impact of:
1991 Cholera outbreak in Peru
- Started in ports

- Continued for 4 years

- TOURISM dropped 60-70%

- EXPORTS canceled and most IMPORTS delayed

- Social breakdown: education, health, and sanitation declined which allowed increased spread
Explain the ECONOMIC impact of:
1993 Pneumatic plague in India
- Small outbreak from rat contact

- Quickly spread through aerosolization

- $1.3 billion overall cost: travel revenue lost, tourism drop, and diamond trade halted
Explain the ECONOMIC impact of:
1996 E.coli in Japan
- Outbreak in 47 elementary schools (children & teachers)

- Radish sprouts in school lunches had E. coli strain

- Costs in prevention, care, screening, trade loss for radishes, victim compensation, lawsuits by radish manufacturers
Explain the ECONOMIC impact of:
1997 Avian flu in Hong Kong
- H5N1 spread from chickens to humans
- Chicken imports halted (all chickens also killed)
- Forced to buy frozen chicken from Thailand (more expensive + IMPORT)
- Tourism declined (travel warnings)
Negative discrimination against people with certain attributes
(i.e. STDs, leprocy, plague, etc.)
Stigma
How does stigma affect the health of society???
- Barriers made between the infected and their treatment (no treatment = increased spread)

- Marginalized by class

- Stigmatized people distrust health officials (no cooperation)

- Distortion of risk (mass panic; bad allocation of health resources)
How was the plague outbreak in India affected by stigma???
- Only 200 cases, 25% mortality (pretty low!)

- 500,000 people fled, including 78% of the medical workers

- Flights/imports banned, ships wouldn't port, trains wouldn't stop

**Stigma was WORSE than the disease**
What are the 3 hypotheses explaining influenza peaks in winter???
1. People are indoors, closer contact
2. The relative humidity allows the virus to be more virulent
3. Decreased immune system responses
Relative humidity varies as a function of what two independent variables?
- Temperature
- Vapor pressure
Explain the FIRST cholera outbreak...
(when, where, why)

When did it finally reach U.S.?
- 1817, heavy monsoons in India brought virus inland.

- Around 1832
What is a cholera serotype?
What is a cholera biotype?
Serotype: related to the antigens on the capsules

Biotype: phenotypes that differ in infection severity
What is SARS?
- "Severe Acute Respiratory Syndrome"
- Spread by Corona virus (aerosolized)
- Quickly transmitted in airplanes and health-care facilites
What viral family is Dengue in???

What diseases does the virus cause?
(order by severity/symptoms)
Flavivirus

Dengue Fever < Dengue Hemorrhagic Fever < Dengue Shock Syndrome
What is the difference between Sylvatic and Endemic transmission???
Sylvatic: incorporates wilderness areas and animals (other than human and mosquito)

Endemic: transmission between mosquito and human only
Explain "antibody dependent enhancement"..............
Situation in which host receives antibody for ONE serotype, and...
1) they have lifelong immunity to THAT ONE serotype, but
2) there is INCREASED severity for the OTHER serotypes.
WHO first isolated Dengue and WHEN?
Albert Sabin, during WW2
What is an "arbovirus"???
A virus transmitted by arthropods (i.e. mosquitoes)
Define PRION diseases (TSEs) and give examples
Slow-growing infectious agent NEITHER bacterium nor virus.

Examples:
Kuru
Scrapie
BSE ("Mad cow disease")
Creutsfeldt-Jakob disease
Explain: Daniel Gajdusek
- Interested in "Laughing Sickness" (Kuru)
- Worked to identify the source and how it developed.
- Showed that scrapie, kuru, and Creutzfeldt-Jakob disease (CJD) were all transmissible, but with long incubation times.
Explain: William Hadlow
- Studied scrapie in sheep
- Noticed similarities between scrapie and kuru.
Explain: Michael Alpers
- Observed tie between the 1950's ban on "transumption" (post-mortem ritual cannibalism) and the decrease in kuru.
Explain: Shirley Lindenbaum
- Learned through interviews/research that kuru first appeared in the 1920's

- Saw also that the consumption of deceased relatives began a few years BEFORE kuru emerged.
Explain: Stanley Prusiner
- Studied CJD, and worked with William Hadlow.

- Found that the "infectious agent" in prion diseases was a PROTEIN, with NO nucleic acids
Explain: Scrapie
- Prion disease
- degenerative disease affecting sheep's/goat's central nervous system
- originated in 1700s in Europe
- diagnosed in 1947 in U.S.
What is THE protein that causes prion diseases?

Where can it be found?
PrP^c

Found on cell membranes of ALL MAMMALS
What are the three modifications done to the prion protein to cause different diseases???
(what are examples for each?)
Sporadic: due to mutation --> CJD

Genetic/familial: inheritance of mutation --> Gerstmann-Starussler-Scheinker syndrome (GSS), Fatal familial Insomnia (FFI)

Infectious/acquired --> CJD (can be transmitted during medical examinations), Kuru, BSE
How is vCJD different from CJD?
vCJD is a "variance"...it the result of ingesting infected meat (i.e. mad cow beef, squirrel brains, etc.)
What is CWD?
"Chronic Wasting Disease"
aka- Mad Deer Disease

Prion disease found in free range deer/moose/etc. in Canada and U.S.
What are the main targets for an antibiotic???
Essential bacterial machines for macromolecular biosynthesis

i.e. cell wall, protein, and nucleic acid synthesis, and folic acid metabolism