Past Test Questions

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-level of virulence
-Non human reservoir?
-Mode of transmission
-Level of reproducibility in host
-Human resistance and suceptibility
-Signif pop immunized with vaccine
-What causes morbidity and mortality
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Terms in this set (49)
-Virulence: high
-Yes reservoir
-Fecal oral rt, contaminated water, contaminated food
-Repro: Upon ingestion, pathogen replicates in gastrointestinal tract. Diarrhea that results can cause the release of a large number of bacteria in the stools.
-Resist: no previous exposure means bacteria is highly infectious. Somebody who recovers develops immunity, but can be reinfected at later times in life, though not as severe
-No vaccine
-Morbidity and mortality results from an induced severe diarrhea that causes massive fluid and electrolyte loss in the patient in just a day or 2.
-Vir: high
-Yes reservoir
-Close contact aerosols
-Repro: Pathogen is inhaled and replicates very rapidly in the lung epithelium. Significant amounts of virus are released in the airways and lungs. These virions are spread by cough, sneeze, nasal drainage, etc.
-Resist: No human immunity bc not enough time to develop. Very infectious and spreads rapidly by aersols.
-No vaccine
-Virus replicates in lungs and kills epithelial cells and induces an inflammatory response that results in fluid accumulation in lungs. Patients die of a virally induced pneumonia
-High RO 5-7
-No reservoir
-Close contact aersols
-Initial replication in lung epithelium with subsequent viremia throughout the body. High levels of virus in tissues and in skin rash papules. Virus can be released when skin lesions erupt by aersols when coughing and sneezing
-Very efficient pathogen, that very likely infects somebody that hasnt been vaccinated. Virus makes many proteins which have the ability to limit a protective immune response
-Not in present day
-Virus replicates at a high level in tissues during viremia phase that many organs do not function properly and many cells are killed. individuals can die of multiple organ failure or from systemic destructive inflammation
-Individual who has a higher level of pathogen replication in vivo than is usual
-Individual who excretes more infectious agent into the environment than is usual.
-Individual who remains infectious for a longer period of time than is usual.
-Individual who does not become incapacitated by disease as is usual, but continues to interact with susceptible individuals while being very ill.
-Individual who interacts with large groups of susceptible individuals while infectious (e.g. an individual in a health care setting with a lot of patients who may have lowered immunity)
-Only one experimental patient (N=1, James Phipps).
-Phipps was a child and was the son of his poor gardener. (Employee exploitation?)
-Challenge of Phipps with smallpox virus was human experimentation that had a high probability of adverse effects based on current knowledge.
-No control patients (mock vaccination, then challenge with smallpox) for comparison, though this would also have been unethical.
-Drew conclusions from this single experiment (N=1, Controls=0) that were unfounded (i.e. no statistical analysis possible) based on the design of this "clinical" trial.
-Had a clear hypothesis, even though he was not sure of the mechanism of cross-protection.
-Had a clear experimental design, with a definitive outcome (i.e. no detectable smallpox).
-Had all the materials he needed to complete the experiment [i.e. a source of fresh cowpox from his milkmaid, a willing experimental subject (victim?) thanks to his gardener, and a source of smallpox from his infected patients).
-Collected the results from this first experiment, and performed additional, similar experiments.
-Published his work.
Advantages: An attenuated infection that caused much less morbidity and mortality than did variolation (infecting with variola); Immunity against smallpox was quite good following vaccination; did not have to have a human with smallpox to inoculate others; during active infection with cowpox (from cow or arm to arm), individual was not very contagious to others, unlike variolation;
Disadvantages: If cowpox for immunization came from animals ("ungodly"), very difficult to keep such material sterile, so cow pathogen contamination was a problem; Cowpox arm to arm technique also caused some problems: If contributing individual also had other infections (e.g. hepatitis, etc.) then these infections could be transmitted to the receiver, Arm-to-arm technique was not always successful if transmitter did not have active lesions (e.g. where do you get live cowpox for vaccination?), No way to know amount of cowpox being transmitted to receiver; a few percent of individuals reacted poorly to cowpox infection; Not lifelong immunity.
Snow did several things that were collectively unique for the 1850s: specifically
- General, accurate observations; used common sense
- Careful research of individual cases to determine what each had been exposed to in an effort to disprove or prove his hypothesis (forensic epidemiology)
- Careful data collection of cases in a geographical area (chartography)
- Statistics (mathematical analysis of the data)
- Drew conclusions based on data (i.e. evidence based conclusions) not beliefs or political correctness (the scientific method)
-Extremely well trained as a physician and as an epidemiologist (for his time)
-Functionally intelligent (i.e. high emotional intelligence)
-Infectious grin, entrepreneurial spirit, diversity of interests,
-Took a chance on the newly formed CDC in Atlanta
-Ability to overcome rules or obstacles that were in his way
-Could be an effective physician, as well as an effective administrator
-Had a desire to become an effective administrator
-Ability to stimulate trust in others that he could lead
-Ability to work with a diversity of researchers, physicians, epidemiologists, etc.
-Agreed to move self and family overseas (did what was necessary)
The young: infants or children who had not been exposed to disease or vaccinated were very susceptible to smallpox. This is especially true for infants as their immune system is still developing. This less effective immune system makes the young generally more susceptible to diseases
The old: with aging, the immune system becomes less functional (immunosenescence). This less effective immune system makes the old generally more susceptible to diseases
Populations that never had smallpox in their geographic region: Such populations were essentially 100% susceptible to smallpox since no one had ever recovered from the disease. Such recovered individuals were immune to further smallpox infection. In the absence of any "herd immunity" the disease could spread rapidly from one person to another.
Immunosuppressed patients (an assumption): As with any infectious disease, the immunosuppressed are usually more susceptible (note: the degree of susceptibility depends upon the type of immunosuppression that the patient has and what the infectious disease is). However in the 1800s and early 1900s, we really did not have a good understanding of the immunosuppressed patient (either genetically or environmentally induced immunosuppression). So....we do not have any really good data on which type of immunosuppression resulted in high susceptibility to smallpox morbidity and/or mortality. So...we assume they were susceptible.
There are two ways that an adult population can acquire "heard immunity" against a particular infectious disease. List both and describe the advantages and disadvantages of each.1) the presence of a significant percentage of the adult population that has recovered from smallpox infection. These individuals are immune to a second infection for the remainder of their lives, and therefore represent a population of protected individuals. Therefore, this is infection-mediated acquisition of "herd immunity" within a population. Problem is that some people will die from the infection and any newborns or children born into the population would be susceptible to disease. 2) the use of vaccinia to immunize a significant percentage of the adult population. The use of vaccination allowed a high percentage of individuals within a population to develop immunity against vaccinia, and this immunity also provided some protection from smallpox. Therefore, this is vaccination-mediated acquisition of "herd immunity" within a population. Disadvantage that protective immunity only lasts 7-10 years. Also, newborns prior to vaccination have no immunity.List each task, in its proper sequence, required to make and use smallpox as a biological weapon.1) obtain a stock of smallpox (variola major) that is most virulent and extremely viable even in storage 2) set up a manufacturing facility with biosafety level 3 capable of producing and storing enough virus 3) hire individuals with expertise in virology and/or large scale manufacturing of biologicals 4) make sure all employees are immunized with vaccinia (must purchase significant amounts of vaccine) 5) since this would be illegal, security clearance and non-disclosure requirements for employees 6) establish a standard operating procedure for manufacturing virus (in chicken eggs or in cell culture) 7) purchase all equipment needed for manufacturing (eggs versus cell culture would be very different) 8) begin manufacturing virus in large quantities, isolate virus, concentrate virus, store virus until needed 9) standard operating procedures to assure that stored virus retains its virulence 10) weaponization: develop a method for delivering the virus that does not destroy the virus, that exposes a significant geographic area, that will affect a large population regardless of environmental conditions, etc. 11) delivery: transport of your biological weapon to the area for deployment and use it as a weaponWhy was the bifurcated needle such an important technological advance for smallpox vaccination?-cheap to make and durable (made of steel) -cheap to use -easy to use (could be used in the field by non-medical or minimally trained individuals) -efficient delivery of vaccinia (required little inoculum and wasted little during vaccination) -less painful than some other forms of immunization (e.g. subdermal injection with needle) -easy to reuse (non-disposable) -easy to sterilize for reuse -low tech, so required minimal training to become proficientIn the 1600s if the family in the farm just down the road got smallpox, what were your options to limit your exposure to disease?Run Forrest, Run. (Moving away from concentrations of disease was a common behavior in this era.) -Sequester yourself or your family and no interact with others (self-quarantine) -Burn candles or fires to remove "bad humors" from the air (of course this did not work!) -Pray to deities, statutes, etc. to protect you from smallpox.Birthday Party Gone Bad Step 1: What to do next? Step 2: Which questions are most important to ask during the interviews? Step 3: What to do next? Step 4: What do most of the patients have in common? Step 5: What activities do you think caused people to get sick? Step 6: What is the most likely explanation for the outbreak of Crptosporidium infections? Include the initial source of the parasite, its mode of transmission in this outbreak, and how future outbreaks of this type might be prevented.1) Ask party guests if they ate cake and ice cream. Call the family who host the party to learn more. 2) What foods did you eat? Did you go swimming at the birthday party? Do you have a weakened immune system? 3) Determine if the new cases are connected to the outbreak from the party. Interview the new patients to see what they have in common. 4)most patients are children 5) Swallowing water from the activity pool 6) The initial source of the parasite was the babies in the swim class on July 31. The likely explanation is that they used the bathroom in the water and through fecal-oral transmission of those swimming in the water acquired the parasite. This can be prevented by blocking infants from using the pool or using extra chemicals to kill the parasite in the water.Diagnosis of ongoing, chronic, or recurring Chagas disease in patients may include:-Clinical symptoms such as Romana's sign (disease-included swelling and edema of the eye lids) -A patient's blood smear showing a parasitemia -The presence of antibodies (of the IgG class) against the Chagas parasite -Positive PCR results for the Chagas parasite DNA in a patient's blood or tissueInfection by the Chagas parasite can be life-threatening in a small percentage of patients-That develop meningoencephalitis when the parasitic infection reaches the brain -That develop myocarditis when the parasitic infection enters heart cells and causes cellular deathPathogen(s) where an active zoonotic cycle is necessary for transmission to humans include(s)West nile virus (NOT malaria, dengue, or chagas)Screens placed on windows or netting placed around an uninfected person's bed-can be effective for preventing: the spread of dengue, chagas, malaria, encephalitisPathogen(s) which must replicate in insects to spread disease to humans include(s)-Malaria parasite -Chagas parasiteParasitemia in humans infected with the malarial parasite-Can cause a large, but not altogether protective immune response, which results in immune-mediated clinical symptoms -Is necessary to maintain the human-to-vector transmission cycleTreating or limiting the spread of Chagas disease within a geographic area can be challenging due to-The lack of an effective vaccine against the Chagas parasite, preventing prophylactic immunization -The presence of high levels of the chagas parasite in the blood stream in some patients for more than a monthPathogens which can frequently cross the placental barrier and damage the fetus during pregnancy include:-Malarial parasite -Zika virus -ChagasRegarding the feeding habits of mosquitoes, which of the following statements is/are true?Usually it is the female adult mosquito that will ingest a blood meal from other animalsElimination of endemic malaria in the southern US in the early 1900s was achieved using which of the following methods?Reduction of mosquito breeding grounds using drainage and managing water levels in reservoirsAdvantages of using of DDT include(s)It is cheap and easy to useRegarding malarial disease, transmission, and deaths in countries with a very high incidence of disease, which of the following statement(s) is/are false?Anti- Malarial drugs have little effect on a patient's disease, especially in countries with high disease incidenceRegarding Culex pipens reproduction cycle, which of the following statement(s) is/are true?Mosquitoes newly emerging from pupae have a difficult time flying until their bodies and wings dry and hardenChallenges to developing an effective vaccine against the malarial parasite include(s)-The rapid movement of the malarial parasite to the patient's liver following initial infection -The different stages of the malarial parasite as it replicates within the patient -A lack of understanding of what a protective immune response against the malarial parasite would look like in the patient: do we vaccinate against intracellular parasites, extracellular parasites, or both? -The complexity and/or variability of the malarial parasite's stage-specific antigen expressionRegarding Malarial parasites released from liver cells of infected patients-This stage-specific malarial parasite invades erythrocytes in the infected patientFactor(s) required for actively expanding zika virus transmission in a geographic area include(s)-A population of Aedes mosquitoes that are actively infected with zika virus -A population of humans that have ongoing zika virus viremia -A population of uninfected humans that are susceptible to zika virus infection -A population of uninfected Aedes mosquitoes that are susceptible to zika virus infectionRegarding herd immunity, what is true?The herd immunity thresholds required for effective containment are directly correlated with the Ro for that particular pathogenYersinia pestis infection in humansCan be transmitted from person to person by aerosol droplets (inhalation)The flu pandemic of 1918-1920Resulted in more deaths due to this H1N1 flu infection than all of the military deaths associated with WW1An outcome of recovery from an initial infection with dengue virus type 1 (type A) followed by a second infection with dengue type 4 (type D) one year later might beClinical symptoms during the 2nd infection that are much worse than the 1st infection and maybe even fatalThe most effective and practical method for reducing the mosquito burden around one's dwelling isSpraying chemical pesticides, such as an adulticideJohn Graunt 1600sRecorded mortality statistics, and divided deaths into acute and chronicThe Framingham Heart StudyFollowed thousands of patients over three decades to draw conclusions about heart disease as a chronic conditionBacillus thuringiensis israelensis (BTI)spores that are eaten by mosquito larvae result in a disruption of gut integrity, causing the larvae to dieIf you were an epidemiologist task with protecting the US from foreign visitors entering the country who had active zika virus infection, what multiple measures would you take? Make sure that each of these measures is practical and realistic.Increase surveillance and tracking of contacts for cases of Zika that arise in the USA and are linked to entry of foreigners or to citizens that have travelled to endemic regions (Possible) Immediate quarantine of patients and immediate contacts for cases of Zika that arise in the USA and are linked to entry of foreigners or to citizens that have travelled to endemic regions (Possible) Educate travelers from the USA to endemic areas about the dangers of Zika infection; maybe hand out DEET wipettes (very possible)Will it be possible to achieve global eradication of the flu virus? Explain why or why not.It is difficult to imagine a scenario where the flu virus will achieve global eradication. Factors include: The presence of flu virus reservoirs in animals pigs, waterfowl, etc. The ability of flu virus strains of animals to jump across species barriers to infect humans The ability of the flu virus to recombine into new strains when multiple strains of flu infect the same animal (e.g. antigenic shift) The ability of the flu virus to infect an individual and produce large amounts of virus in a short period of time. This rapid dissemination occurs before an effective immune response can develop The ability of any one flu virus strain to slowly alter (mutate) its main antigens (hemagglutination, HA, and neuraminidase, NA) over time (antigen drift) to thwart a protective, developing immune response The reinfection of individuals that have recovered from a flu infection by flu viruses of different (antigenic shift) or mutated (antigenic drift) strains The lack of an effective vaccine that can protect against all strains or substrains of flu viruses present in the population The lack of an effective vaccine that can protect against all strains or substrains of flu viruses present in the population for many years with only one immunization Lots of money and international cooperation would be requiredWhat parasite causes chagas diease? How are uninfected humans exposed to this parasite?Trypansoma cruzi. Gastric passage Triatomine sp. are infected with the parasite following a blood meal from parasitemic human Epimastigotes grow in midgut; trypomastigotes grow in hindgut When taking a blood meal, trypomastigotes are defecated onto human skin Human rubs trypomastigotes into wound or onto mucus membrane to become infected In rare cases, can be exposed by receiving tissue or blood from infected donor or trans-placentalWhat were the most compelling arguments that scurvy was not an infectious disease?-The disease was especially prevalent among sailors . This fact did not fit with historical examples of infectious epidemics (e.g. smallpox) that caused disease throughout a population. -High incidence of disease could be linked to limited diets. An experiment by James Lind in the mid 1700s showed that adding citrus fruit to the diet of sailors eliminated the development of scurvy. It is difficult to image how such a result could be consistent with an infectious disease. -Following Dr. Lind's observations, British sailors were required to consume limes. Again, this addition in diet that eliminated scurvy is inconsistent with an infectious etiology.What is a "carrier" of an infectious disease? Give on infamous example of a carrier and explain how this individual was identified.Typically, this is an individual who is infected with a pathogen (maybe chronically), but has few, or no, clinical symptoms of the disease typically resulting from this pathogen (i.e. subclinical disease). Typhoid Mary (Mary Mallon) was one infamous example. She was identified initially by correlation; wherever she worked, people around her came down with typhoid fever. She was ultimately identified as a chronic carrier when this pathogen was found in her feces using microbiological assays even though she had no symptoms of the disease.In the early 1990s, what factors resulted in the reemergence of TB as a global disease epidemic?1) Emergence of drug resistant TB strains: Very Drug Resistant (VDR), Extremely Drug Resistant (XDR), etc. With strains which are difficult to treat with antibiotics, there is little drug therapy available to keep them from spreading. 2) increasing numbers of individuals who have some environmentally-induced immunosuppression. Immunosuppressed patients are much more susceptible to TB infections e.g. increasing numbers of individuals who are undergoing cancer chemotherapy which is often immunosuppressive e.g. infected with HIV, causing immunosuppression over time 3) a continuing increase in global travel/immigrationHow can a geographic area that already has endemic malarial disease have an epidemic of malarial disease?Some event causes an increase in the number of cases in that region in a defined time frame which is well above endemic levels: Events might include: an environmental change (e.g. an especially wet or warm spring causing an increase in the mosquito population; the introduction of an especially virulent strain of malaria into an endemic area; emergence of pesticide resistant strains of Anopheles into an endemic area; influx of immigration into an endemic area bringing additional malarial disease or hosts; surge in birth rates over a period of time producing a population susceptible to malarial disease; etc.List 2 observations that Dr. Patrick Manson made and why they were important.Filarsis could be found in mosquitoes and in humans. This is important because it shows they could infect each other creating a slyvatic cycle because filarsis is capable of replicating in both.In mosquito-borne disease, 3 factors exert a powerful influence on the equation that leads to the basic reproductive number.A) Vector abundance or population density of the mosquito that carries a disease B) Focused feeding or the mosquitoes' tendency to bite people and nothing else C) Vector longevity. Will the mosquito live long enough to acquire pathogen and then properly deliver it, via bite, to people?African Epidemic Activity 1) What would the best course of action be? 2)What group(s) is/are most affected by Ebola? 3)How to balance spread with burial traditions? 4)How to prevent Ebola outbreak from spreading?1)Talk further with the people who saw the traditional healer 2) All groups listed 3) begin to educate people regarding safe practices 4) screen travelers for symptoms before leaving and after arriving