lmcc 2008 review- infectious disease epidemiology.ppt

Part III: Infectious Disease Epidemiology

Epidemiological Triad for Infectious Disease

Notifiable DiseasesAcute Flaccid Paralysis AIDS Amoebiasis Anthrax BotulismBrucellosis Campylobacteriosis Chancroid Chickenpox Chlamydia, Genital Cholera Creutzfeldt-Jakob Disease Cryptosporidiosis Cyclosporiasis Diphtheria Giardiasis Gonorrhea Gonococcal Ophthalmia Neonatorum Group B Streptococcal Disease of the Newborn Hantavirus Pulmonary Syndrome Hepatitis A Hepatitis B Hepatitis C Hepatitis Non-A, Non-B Human Immonodeficiency Virus Influenza,Laboratory-Confirmed Invasive Haemophilus influenzae type b Disease Invasive Group A Streptococcal Disease Invasive Meningococcal Disease Invasive Pneumococcal Disease Legionellosis Leprosy Listeriosis (all types) Malaria Measles Meningitis, Pneumococcal Meningitis, Other Bacterial Meningitis, Viral Mumps Paratyphoid Pertussis Plague* Poliomyelitis Rabies Rubella Rubella, Congenital Salmonellosis Shigellosis Smallpox Syphilis, All Syphilis, Congenital Syphilis, Early Latent Syphilis, Early Symptomatic (Primary and Secondary) Syphilis, Other Tetanus Tuberculosis Tularemia Trichinosis Typhoid Verotoxigenic E. coli1990 -Viral Hemorrhagic Fevers (Crimean Congo, Ebola, Lassa, Margurg) West Nile Virus Asymptomatic Infection West Nile Virus Fever West Nile Virus Neurological Syndromes West Nile Virus Unclassified/ Unspecified Yellow Fever

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Emerging communicable disease

Cryptosporidium parvum 1976 Ebola virus 1976 Legionella 1977 Campylobacter jejuni 1977 E. Coli 0157:H7 1982 HIV 1983 Hepatitis C 1989 nv CJD 1996 Avian influenza ( Type A H5N1) 1997 WNV 1999 SARS 2003 ……… Pandemic influenza???

Basics of Disease Transmission

Chain of Infection

Contact (Host)

Reservoir

Agent

Environment

Iceberg of infectious disease

Course of Disease

Incubation period Illness

Infected Infectious

Latent Period

ImmunityActive

infection immunization

Passive immunoglobulin intrauterine

Herd Immunity

Portals of Entry for InfectionRespiratory tractGenitourinary tractGastrointestinal tractSkin / Mucous membraneTransplacentalParenteral( percutaneaous , via blood)

Modes of Transmission

Direct Direct contact (bite,soil,touch) Droplet spread Vertical transmission (through

placenta)

Indirect Airborne (droplet nuclei , dust

particles) Vehicle borne (food, water) Vector borne ( mosquito) Mechanical ( flies)

Opportunities for interrupting transmission

Immunization

Infection control

Treatment

Isolation

Chemoprophylaxis

Improve general environment

Vehicle control Quarantine

Herd immunity

Physical protection

Opportunities for interrupting transmission

Reservoir Infection control measures,treatment,isolation

Susceptible contact chemoprophylaxis, immunization (active and

/or passive),quarantine , physical protection Route of transmission

food preparation , water purification, vector control

Agent Infection control measures, treatment

Investigation of disease outbreaks

Epidemics Epidemics are temporary increases in the

incidence of disease in populations• E.g. Infectious Disease- SARS, West Nile Virus• E.g. Non-infectious Disease- Asthma deaths in the

1960s associated with increased use of pressurized aerosol broncholdilators

Increases in incidence are usually significantly above the level expected from past experience in the same population

Epidemics and OutbreaksThe occurrence of cases of an illness clearly in

excess of expectancy

Examples of recent epidemics: HIV / AIDS- Retrovirus; Ebola- African filovirus via monkey; causes viral

hemorrhagic fevers (VHF); often fatal; Hanta virus (US)- Bunyavirus via rodents; causes

severe infections of the lungs and kidneys; Lyme disease (US)- Borrellia burgdorferi bacteria

via tick bite; symptoms include: fatigue, fever, stiff muscles/joints, meningitis, arrhythmias, arthritis.

Definitions Primary or index case- the first case (or group of

cases) arising from the introduction of an agent in to a community

Secondary case- people who acquire infection from the primary case(s)

Incubation period- the time interval between infection of an individual and the onset of symptoms

Generation time- the time interval between the onset of primary and secondary cases

Derived infection- this is an infection arising by direction transmission from an infected contact

Types of Epidemic There are two main types of epidemic: common

source and propagated Point or Common Source Epidemics- result from

the exposure of a group of people to the same source of infection or noxious substance. Continuous exposure or intermittent exposure of the population to the causal agent produces a more extended and irregular epidemic curve. • E.g. outbreak of Salmonella typhimurium food

poisoning amongst delegates ate a medical conference• E.g. outbreak of respiratory disease due to adulterated

cooking oil in Spain

Propagated (Person-Person) Epidemics

• Propagated epidemics are due to the transmission of infectious agent from one person to another. The epidemic curve usually shows a gradual rise and decline, often with further waves as each successive generation of cases infects a new generation.

•E.g. An outbreak of measles occurred in a primary school. After two index cases , there were two epidemic waves at approximately 10-14 days intervals. The outbreak was modified by those vaccinated. The attack rate among those unvaccinated was 86%.

Investigation of an OutbreakStages In Investigation

• Descriptive enquiries into the facts of the outbreak

• Investigative reservoirs and vehicles of infection

• Analysis of the data collected• Formulation of a causal hypothesis• Testing its validity in the control of the

outbreak

Descriptive enquiries Verify the diagnosis by clinical and laboratory

investigations Verify the existence of the epidemic by

comparison with previous incidence of the disease in the same population

Compile a list of all cases Investigate patients and others who might be

involved in the case (i.e. age, sex, occupation, address etc.)

Ensure all clinical and laboratory investigations required to confirm the identity of the infection in patients were carried out

Investigate reservoirs and vehicle of infection

Human- an epidemic may originate from an individual who a minor clinical episode or is a carrier of disease

Animal- enquire about the contacts patients may have had with sick animals or animal products

Environment- investigate sources of foods consumed by individuals and the circumstances of their production, storage, preservation and preparation. Arrange for laboratory examination of food, water supplies and other environmental sources and typing of any organisms that are isolated

Analysis of the data collected

Plot of the epidemic curve- this may give some clue to the mode of spread and probable time of initial exposure

Plot the cases on a map- this will detect clustering and the distribution of cases

Analyze the incidence rates in different groups- for example by age, sex or occupation. Attack rates must be calculated among both exposed and non-exposed

Look for a quantitative relationship- this may exist between the degree of exposure (or dose) and attack rate

Formulation of a causal hypothesis

Factors for hypothesis:• The properties of the agent, it’s reservoirs, favored

vehicles and the nature of illness• The probable source and route of transmission• Time and duration of exposure of the patients to

the agent in relation to the onset of their illness• Attack rates of the different sub-groups of the

population at risk

Testing validity in the control of the outbreak

Seek support for the causal hypothesis by further investigation of cases, if necessary, to confirm the proposed explanation of their illness

Implement appropriate control measures on the assumption that the hypothesis is correct and monitor their success in reducing the incidence of further cases

Epidemic Curves # cases by time of onset Shape of the curve gives you clues: Agent known: use incubation period to look

back at exposure Agent unknown (but common event likely):

postulate agent by determining the incubation period

Draw the curve relative to specific sites/groups

Epidemic Curves: Point Source

0

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CASES

Hours

Salmonellosis in passengers on a flight from London to the US by time of onset, March 13-14, 1984

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Index case

Hours since exposure

Epidemic Curve: Propagated or Person-Person

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# CASES

Days since exposure

Index Case

SecondaryCases

TertiaryCases

VHF Deaths, Bandudo Province, ZaireMarch - April 1995

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3/27/1995 4/10/1995 4/24/1995 5/8/1995

Date of Death

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Epidemic Curve: Continuous Source Outbreak

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DATE

CASES

Occurrence/Cessation of an Outbreak

There are numerous conditions that might change and precipitate an outbreak, although all lead to an increase in the number of exposed and susceptible persons required for an outbreak. Some include:• The new appearance of or sudden increase in an

infectious agent or toxic material• The arrival of susceptible to an environment

which has an endemic pathogen• The introduction of an effective route of

transmission from source to susceptible (e.g. climatic change and malaria)

Question 1.The quarantine or surveillance periodprescribed for a specific infectious disease is based upon:

(a) Incubation period of the disease(b) Epidemic cycle of the disease

(c) Period of infectivity of the disease(d) Normal maximum duration of acute

symptoms(e) Proportion of susceptibles in the

contact population

Question 1.

Answer

(a) Incubation period of the disease

Question 2.The isolation period prescribed for a specific infectious disease is based upon:

(a) Incubation period of the disease(b) Epidemic cycle of the disease(c) Period of infectivity of the disease(d) Normal maximum duration of acute

symptoms(e) Proportion of susceptibles in contact

population

Question 2.

Answer

(c) Period of infectivity of the disease

Question 3.When is the isolation of infectious disease cases most useful as a method of preventing new cases?

a) During the period before the onset of clinical diseaseb) When the ratio of unapparent to apparent cases is

highc) During period of greatest communicability occurs

after onset of the diseased) Isolating cases of infectious disease is never a

useful method of preventing new casese) Isolating cases of infectious disease is always a

useful method of preventing new cases

Question 3.

Answer

(C) During period of greatest communicability occurs after onset

of the disease

Question 4.An outbreak of measles occurred in an elementary school with an enrolment of 300 pupils. During October and November, 72 pupils in the school were absent with measles.

(a) Compute the attack rate for October and November

The 72 pupils with measles had a total of 100 brothers and sisters living at home. Of the siblings, 20 subsequently developed measles during October through December.

(b) Compute the secondary attack rate among the siblings.

Question 4.

Answer

(A) 24%

(B) 20%

Question 5.

With one exception, all the following diseases are notifiable in Saskatchewan. The one exception is:(a) HIV infection(b) Gonorrhea(c) Non‑gonococcal urethritis(d) Chancroid(e) Chlamydia

Question 5.

Answer

(c) Non‑gonococcal urethritis

Question 6.In Canada, which of the following methods of transmission apply

BEST to each of the four diseases mentioned below?

(a) Person‑to‑person(b) Foodborne(c) Airborne(d) Waterborne(e) Bloodborne

____ salmonellosis____ hepatitis A____ psittacosis____ hepatitis B

Question 6.

Answer

B salmonellosis

A hepatitis A

C psittacosis

E hepatitis B

Question 7.

The Culex tarsalis mosquito is the vector in:

(a) Malaria

(b) Typhus

(c) Western equine encephalitis

(d) Yellow fever

Question 7.

Answer

(c) Western equine encephalitis

Question 8.

The A.I.D.S. (Acquired Immune Deficiency Syndrome) is due to a HIV infection. The mode of transmission for HIV infection is similar to:

(a) Hepatitis A

(b) Tuberculosis

(c) Typhoid

(d) Hepatitis B

(e) None of these

Question 8.

Answer

(d) Hepatitis B

Question 9.

Notification of infectious disease is the duty of:

(a) The attending physician

(b) A teacher or principal

(c) A nurse providing professional services

(d) The manager of a medical laboratory

(e) All of the above

Question 9.

(a) The attending physician

Question 10.With one exception, all of the following are

notifiable communicable disease under Saskatchewan public health legislation. The one exception is: (a) Food poisoning(b) Diphtheria(c) Measles(d) HIV infection(e) Pneumococcal pneumonia

Question 10.

Answer

(e) Pneumococcal pneumonia

Question 11.

Communicable disease control in a population may be brought about by:

(a) Reduction in size of disease reservoir

(b) Increasing host resistance

(c) Limiting transmission of disease

(d) Chemoprophylaxis


Question 11.

Answer


Question 12.A reduction in the size of the disease reservoir is basic to prevention of disease. Such a principle has been successfully applied to the control of:

(a) Hepatitis B (b) Gonorrhea(c) Syphilis(d) Salmonellosis(e) None of the above

Question 12.

Answer

(e) None of the above

Question 13.The most important cause of the decline in United States tuberculosis mortality rate from 194 per 100,000 in 1900 to 23 per 100,000 in 1950 was:

(a) Immunization(b) Chemotherapy(c) Environmental sanitation(d) Aging of the population(e) Improvement in general social

conditions

Question 13.

Answer

(e) Improvement in general social conditions

Question 14.Immunization, testing of herds and destruction of infected animals has been applied to the control of brucellosis. It is an example of infection control by:

(a) Interrupting the transmission of organisms

(b) Reducing host susceptibility(c) Reducing the size of the reservoir(d) All of these(e) None of these

Question 14.

Answer

(c) Reducing the size of the reservoir

Question 15.A child has been bitten by a dog. Which of the following factors

would you take into account in deciding what action to take?

(a) If the bite were on the head or neck

(b) The child provoked the animal (e.g. poke with a stick)

(c) The child knew the animal and its normal residence

(d) The dog has shown abnormal behaviour over the last 24 hours


Question 15.

Answer


Immunization

Immunization of Travellers Required Immunizations

Yellow fever Meningococcal disease Cholera

Recommended Immunizations Hepatitis A Typhoid Meningococcal disease Japanese encephalitis Cholera Influenza BCG

Vaccines Recommended for All Health Care Workers

Diphtheria and tetanus toxoidMeasles vaccinePolio vaccineRubella vaccineHepatitis B vaccine Influenza vaccine

Question 16.A child of 4 months of age has had its second dose of DPaT (Adsorbed) Vaccine. Mother reports that three hours after receiving the immunization, the child screamed for about 12 hours. She was unable to console him. For the third immunization in the series, you would use:

(a) DPaT Adsorbed(b) Diphtheria only(c) Tetanus only(d) Pertussis only(e) DT (Adsorbed)

Question 16.

Answer

(a) DPaT Adsorbed

Question 17.Which of the following is not a contraindication to the use of live vaccine?

(a) Pregnancy(b) Immunosuppression (drug induced)(c) Immunocompromised host (disease

induced)(d) History of allergy to house dust

Question 17.

Answer

(d) History of allergy to house dust

Question 18.Canadian provinces have introduced the adsorbed vaccine for many of their childhood immunizations. One of the main advantages of the adsorbed vaccine DPT are:

(a) It can be given subcutaneously(b) It has a longer lasting effect than the

plain vaccine(c) It can be taken intranasally(d) They are 100% effective(e) They cause fewer side effects

Question 18.

Answer

(e) They cause fewer side effects

Question 19.A 27 year old woman presents with a minor

wound caused while gardening. She has had no immunization since completing a full course of childhood immunizations. You would administer:

(a) DPaT vaccine (b) Tetanus and diphtheria toxoid (Td) (c) Tetanus toxoid alone (d) Tetanus immune globulin (e) None of the above

Question 19.

Answer

(b) Tetanus and diphtheria toxoid (Td)

Question 20.

Mortality rates in Canada for diphtheria have declined from 20/100,000 in 1921 to 0.02 in 1970. The most important cause for this was:

(a) Immunization

(b) Chemotherapy

(c) Environmental sanitation

(d) Aging of the population

(e) Improved standard of living

Question 20.

Answer

(a) Immunization

Question 21.Case fatality from diphtheria is as great now as 50 years ago. But there are fewer deaths from diphtheria in Canada because:

(a) Antitoxin is more easily available(b) The organism is sensitive to penicillin(c) Fewer cases of diphtheria occur now(d) There is better reporting of cases(e) Early diagnosis of diphtheria occurs

currently

Question 21.

Answer

(c) Fewer cases of diphtheria occur now

Question 22.The rubella vaccine currently used in Canada is a live vaccine which produces a good antibody response. Contra‑indications to its use are:

(a) Pregnancy(b) Infants whose mothers are

pregnant(c) Male interns working in obstetrics(d) All of the above(e) None of the above

Question 22.

Answer

(a) Pregnancy

Question 23.

Which of the following diseases has a non-human reservoir?

(a) Typhoid

(b) Shigellosis

(c) Smallpox

(d) Salmonellosis

(e) None of the above

Question 23.

Answer

(d) Salmonellosis

Question 24.In a national vaccine trial, the incidence rate of poliomyelitis was 16/100,000 for vaccinated children and 57 for children who received the placebo. The effectiveness was, therefore:

(a) 45%(b) 70%(c) 72%(d) 79%(e) 87%

Question 24.

Answer

(c) 72%

Question 25.Following a bite from a skunk in an area where rabies is endemic, the physician should:

(a) Ensure immediate washing and flushing of the wound, preferably with soap or

detergent(b) Administer rabies immune globulin

immediately(c) Administer rabies human diploid cell

vaccine immediately(d) Report the case to public health(e) All of the above

Question 25.

Answer


Question 26.Chronic carriers may be important in infectious disease epidemics. Which of the following diseases can produce a chronic carrier state?

(a) Smallpox(b) Hepatitis B(c) Hepatitis A(d) Pertussis(e) None of the above

Question 26.

Answer

(b) Hepatitis B

Question 27.People over 65 years of age have a higher incidence of tuberculosis than do young adults because:

(a) Their diets are poorer(b) They live under more crowded

conditions(c) They were exposed to more

tuberculosis infection in childhood(d) Their disease is more often

reported(e) None of the above

Question 27.

Answer

(c) They were exposed to more tuberculosis infection in

childhood

Question 28.The number and percent distribution of tuberculosis deaths by age for white males in the U.S.,1955 is as follows:

% OF ALL DEATHS AGE DEATHS IN EACH AGE GROUP under 1 21 0.2 1‑ 4 32 0.1 5‑14 14 0.2 15‑24 92 1.0 25‑34 470 5.2 35‑44 993 11.1 45‑54 1858 20.7 55‑64 2246 25.1 65‑74 2152 24.0 75‑84 913 10.2 85+ 167 1.9 8958 100%

Question 28.The inference that tuberculosis mortality rates in extreme old age are lower than they are in persons who are not so old is:

(a) Correct(b) Incorrect because of failure to

distinguish between incidence and prevalence

(c) Incorrect because a percentage distribution is used when a rate is

required to support the inference(d) Incorrect because of failure to

recognize a possible cohort phenomenon(e) Incorrect because there is no control or

comparison group

Question 28.

Answer

(c) Incorrect because a percentage distribution is used when a

rate is required to support the inference

Question 29.Typhoid fever is characterized by the following:

(a) Domestic animals are reservoirs of S. Typhi(b) Less than 1% of typhoid fever patients will still

discharge typhoid bacilli three months after the onset of their disease

(c) Cholecystectomies are recommended for typhoid patients who are still carrying the typhoid bacillus three months after onset of the illness

(d) Typhoid vaccine is not an important means of controlling typhoid fever in developed

countries

Question 29.

Answer

(d) Typhoid vaccine is not an important means of controlling typhoid fever

in developed countries

Question 30.

The screening test for HIV infection used by the Red Cross Blood Transfusion Services tests for:

(a) HIV antigen

(b) HIV antibody

(c) T Helper T Suppressor ratio

(d) A combination of the above

Question 30.

Answer

(b) HIV antibody

Question 31.

What is the estimated risk of a child born to an HIV positive mother becoming HIV positive?

(a) Nil

(b) 100%

(c) 20 - 25%

(d) 80 - 90%

Question 31.

Answer

(c) 20 - 25%

Question 32.

B.C.G. vaccination is an example of immunization using:

(a) A live virus vaccine

(b) A killed vaccine

(c) A live attenuated bacillus

(d) A killed bacterial culture using a bacterial product

Question 32.

Answer

(c) A live attenuated bacillus

Question 33.

Pediculosis pubis is an infestation by the crab louse. It is commonly found in all but one of the following areas:

(a) Pubic hair(b) Perianal hairs(c) Scalp(d) Eyelashes(e) Axillae

Question 33.

Answer

(c) Scalp

Question 34.

Which of the following disease epidemics can be controlled by immunization of the population?

(a) Typhoid(b) Polio(c) Cholera(d) Cryptosporidiosis(e) None of the above

Question 34.

Answer

(b) Polio

Question 35.In a point source epidemic all cases will present:

(a) Within the infectious period of the source

(b) Within the range of minimum and maximum incubation periods of

the disease(c) Within the minimum incubation period of

the disease(d) Within the maximum incubation period

of the disease(e) At one point in time

Question 35.

Answer

(b) Within the range of minimum and maximum incubation periods of the disease

Question 36.Which of the following statements are not true about the

West Nile virus?(a) The West Nile virus can be transmitted

by culex mosquitos.(b) Human transmission of West Nile virus

is possible(c) The main reservoir for West Nile virus is

horses(d) 80% of people infected with West Nile

virus are asymptomatic(e) Crows play an important part in the

surveillence of West Nile virus

Question 36.

Answer

(c) The main reservoir for West Nile virus is horses

Question 37.It has been reported that approximately 13% of refugees from south east Asia have a positive test for Hepatitis B surface antigen (HBsAg). However, other groups in our community are recognized as having rates equal to or greater than those of the south east Asian refugee. Such groups would be:

(a) Physicians(b) Injection drug users(c) Microbiologists(d) Physiotherapists(e) Laboratory technicians ‑ chemical

pathology

Question 37.

Answer

(b) Injection drug users

Question 38.The control of epidemics by isolation of cases is of little value if the disease produces a large number of sub-clinical infections. Examples of such a diseases would be:

(a) Tuberculosis(b) Infectious Hepatitis A(c) Polio(d) Cholera(e) All of the above

Question 38.

Answer


Question 39.The following represents the epidemic curve for 24 cases of Hepatitis A.

It is an example of:(a) Person to person

spread(b) Possible point source epidemic(c) A recurrent food borne outbreak(d) None of the above

Question 39.

Answer

(b) Possible point source epidemic

Question 40.Examine the graph of an epidemic curve. The cases in this epidemic all have gastrointestinal complaints. Which of the following is the most likely cause of the epidemic?

(a) Staphylococcal food poisoning

(b) Salmonella

(c) Influenza‑like virus

(d) A spill of a toxic chemical into the area's water supply

(e) Pollution of the air by a toxic chemical from a

nearby paint factory

Question 40.

Answer

(b) Salmonella

Question 41.In 1967 WHO started a program of smallpox eradication. This was successful because:

(a) Sub‑clinical cases occur commonly(b) Humans constituted the only

reservoir(c) Vaccine effectiveness is not easily

measured(d) 100% vaccination has been

possible in the developing countries

Question 41.

Answer

(b) Humans constituted the only reservoir

Question 42.Which of the following factors contributed to the global eradication of smallpox?

(a) There were no sub-clinical cases(b) Immunization was highly effective(c) Isolation of clinical cases was

effective in preventing transmission(d) Action was organized at an

international level(e) All of the above

Question 42.

Answer


Question 43.

An adult patient of yours is going to Central Africa. What immunization(s) should be considered?

(a) Gonorrhea (b) Malaria (c) Yellow fever(d) West Nile virus(e) All of the above

Question 43.

Answer

(c) Yellow fever

Question 44.

For adult travellers from Canada to malarious areas, which of the following would not be considered for prophylactic use?

(a) Mefloquine

(b) Chloroquine

(c) Malarone

(d) Doxycycline


Question 44.

Answer


Question 45.

A certificate for yellow fever is required by one of your patients who is travelling to South America. After primary vaccination the certificate will be valid after:

(a) 3 days

(b) 6 days

(c) 10 days

(d) 14 days

Question 45.

Answer

(c) 10 days

Question 46.

Maximum time from intercourse with a person infected with syphilis to the development of a primary chancre is:

(a) Three weeks(b) Three months(c) Six months(d) One year(e) None of the above

Question 46.

Answer

(b) Three months

Question 47.

Chlamydia trachomatis infection has been associated in females with:

(a) Chronic pelvic pain

(b) Infertility

(c) Pelvic inflammatory disease

(d) Ectopic pregnancy


Question 47.

Answer


Food Poisoning

Food Poisoning- causes Staph aureus E. coli enteritis Salmonella Shigella Campylobacter Cholera Botulism Mushroom poisoning Listeria Bacillus cereus Fish poisoning Yersinia

Question 48.Bacillus cereus is a recognized agent of food poisoning. The food most likely to be contaminated with this agent is:

(a) Hamburger meat (b) Shellfish (c) Rice(d) Potato Salad (e) Chicken(f) Home-made canned vegetables

Question 48.

Answer

(c) Rice

Questions 49-54.Match each of the following with the food listed.

49. B. cereus 50. E. coli (0l57)51. Demoic Acid 52.

Staphylococcus 53. Salmonella 54. Clostridium

botulinum

(a) Hamburger meat (b) Shellfish (c) Rice(d) Potato Salad (e) Chicken(f) Home-made canned vegetables

Questions 49-54.

Answers

49- c

50- a

51- b

52- d

53- e

54- f

Question 55.Within 30 minutes of eating a bouillabaisse containing tuna, mackerel and shellfish, the subject became flushed, developed urticaria and abdominal cramps. The most likely cause was:

(a) Scrombotoxin (histamine) (b) Staphylococcal toxin (c) Clostridrium perfringens(d) Salmonella(e) Botulinum toxin (f) Shigella (g) Campylobacter

Question 55.

Answer

(a) Scrombotoxin (histamine)

Question 56.

66. One method of pasteurisation is to hold the product at 71.6oC for 15 seconds. This treatment can be relied on to:

(a) Kill spoilage organisms only

(b) Kill most pathogenic bacteria

(c) Sterilize the product

Question 56.

Answer

(b) Kill most pathogenic bacteria

Question 57.Which of the following statements about scabies are true? (Check any number)

(a) Now an uncommon condition (b) Always associated with poor personal

hygiene (c) Characterized by relentless itching,

more intense by day. (d) Distribution of rash characteristically

between fingers, around wrists, and in flexures and buttocks.

(e) Spread by personal contact (f) Persons who are re-infected develop

symptoms within 1-4 days

Question 57.

Answer

True- d, e, f

Questions 58-67.

An outbreak of illness from West Nile virus infection took place in the northeastern United States between July and October, 2001.

For each of the numbered situation below, select the most appropriate term from the following lettered options. Each option can used once, more than once or not at all.

A. EpidemicB. Sentinel caseC. Incidence rateD. RiskE. False- positiveF. False- negativeG. Risk factorH. Prognostic factorI. Natural historyJ. Case fatalityK. Median survivalL. Randomized controlled clinical trialM. Cohort studyN. Case-control study

Question 58.

Persons with fever/headache were ten times more likely than others to have serum evidence of WNV. Fever/ headache is best described as

Question 58.

G. Risk factor

Question 59.

Among Staten Island residents 2.5 per 100,000 persons developed severe WNV neurologic disease during this time period. This measure best described as

Question 59.

C. Incidence rate

Question 60.

WNV has occurred for the first time in the United States the preceding year. This unusual pattern of occurrence is best described as

Question 60.

A. Epidemic

Question 61.

A person who has the symptoms consistent with severe WNV neurologic disease, but does not have definitive serologic evidence of infection

Question 61.

E. False-positive

Question 62.

Two of 21 patients with severe WNV neurologic disease died. This best described by

Question 62.

J. Case fatality

Question 63.

The first person with severe WNV neurologic disease died. This is best described by

Question 63.

B. Sentinel case

Question 64.

Clinical outcome of severe WNV nerologic disease was substantially worse for elderly patients. Advanced age is best described as

Question 64.

H. Prognostic factor

Question 65.

A study of antiviral agents is conducted for the treatment of severe WNV neurologic disease in which treatment assignments to individual patients are made by chance

Question 65.

L. RCT

Question 66.

A study is conducted comparing prior use of mosquito repellent by persons with and without severe WNV neurologic disease. This best described as

Question 66.

N. Case-control study

Question 67.

A study is conducted in which the rates of subsequent WNV infection are compared in communities with and without mosquito abatement programs. This best described as

Question 67.

M. Cohort study

lmcc 2008 review- infectious disease epidemiology.ppt

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