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Virology > Unit 2 - Lecture 12 Viral Epidemiology > Flashcards

Unit 2 - Lecture 12 Viral Epidemiology Flashcards

1
Q

What are the terms of Epidemiology?

A
  1. Study
  2. Distribution
  3. Determinants
  4. Health-related states
  5. populations
  6. control
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2
Q

Define Study?

A

Study: epidemiology is a highly quantitative discipline based on principles of statistics and research methodologies

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3
Q

What is Distribution?

A

Distribution—frequencies and patterns of health events within groups in a population (“when”, “where”, and “whom”).

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4
Q

What are Determinants?

A

Determinants—search for causes or factors that are associated with increased risk or probability of disease (“how” and “why”).

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5
Q

What are health-related states?

A

Health-related states—applied to the whole spectrum of health-related events, which includes chronic disease, environmental problems, behavioral problems, and injuries in addition to infectious disease.

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6
Q

What are populations?

A

Populations— epidemiology deals with groups of people rather than with individual patients.

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7
Q

What is a control?

A

Control—data steers public health decision making and aids in developing and evaluating interventions to control and prevent health problems.

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8
Q

What is an Endemic?

A

Endemic—diseases that persist at a moderate or steady state level within a given geographic area.

ex: Chicken Pox in US
- malaria is not endemic to US

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9
Q

What is Epidemic?

A

Epidemic—an unusually high number of cases in excess of normal expectation of a similar illness in a population, community or region.

Ex: Seasonal influenza, yellow fever (1793), cholera (1865) dengue in bolivia (2009)

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10
Q

What is pandemic?

A

Pandemic: a worldwide epidemic

ex: 1918 influenza, HIV and smallpox

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11
Q

What is Sporadic?

A

Sporadic—disease outbreaks that have no pattern of occurrence in a given time or location.

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12
Q

What is incidence?

A

Incidence—measurement of morbidity; the number of new cases of a disease that occurs in a specified period of time in a susceptible population; usually expressed per 1000 persons

There is an equation!

Incidence rate = number of new cases of a disease in a population during a specified time frame / number of persons exposed to risk to developing disease during a specified time frame x1000

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13
Q

What is Prevalence?

A

Prevalence—measurement of all individuals affected by a disease at a specified time; also recorded per 1,000 persons

Equation:

Prevalence = number of cases of disease present in a population during a specified time frame / Number of persons at risk of having disease at a specified time frame

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14
Q

What is Morbidity?

A

Morbidity: refers to an illness or disease state

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15
Q

What is Mortality?

A

The number of deaths correlated with a particular disease during a given time frame

Mortality rate:

Mortality rate = Number of deaths in a population during a specified time frame / number of persons in the population during a specifiied time frame

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16
Q

What is the Incubation period?

A

Incubation period is the time between infection with a virus and the onset of symptoms.

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17
Q

What is the prodromal period?

A

Prodromal period - first appearance of mild or nonspecific signs and symptoms of an illness.

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18
Q

What is Mode of Tranmission?

A

Mode of transmission—how an infectious disease is spread or passed on.

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19
Q

What is Etiological agent/pathogen?

A

Etiological agent/pathogen—disease causing agent.

20
Q

What is the Reservoir?

A

Reservoir—where the etiological agent lives, grows, and multiplies (e.g., human, animal or arthropod).

21
Q

What is a Case definition?

A

Case definition—a standard set of criteria that is used to identify who has the disease being studied.

22
Q

What is Communicable Period?

A

Communicable period—time period when an infected individual or animal is contagious and he/she can directly or indirectly infect another person, animal, or arthropod.

23
Q

What is convalescence?

A

Convalescence—the recovery period after an illness

24
Q

What is Zoonosis?

A

Zoonosis—any infection or infectious disease transmissible from animals to humans.

25
Q

What is the History of Epidemiology?

A

Pioneers of epidemiology
Their important observations and actions led to disease prevention:

Edward Jenner (1796, smallpox)

John Snow (1854, cholera)

Florence Nightingale (1855, mortality rates of wounded British soldiers during the Crimean War)

26
Q

Who is John Snow?

A

John Snow (1813-1858)

  • 19th century physican
  • Believed in the germ theory of disease during a time period when most people believed in the miasmatic theory
  • Miasma: polluted gases from swamps or decaying matter that cause disease
  • Groundwork for descriptive epidemiology
27
Q

Who is Florence Nightingale?

A
  • Credited mostly for her modernizing nursing practices of the times
  • Collected statistics and mapped mortality rates of British soldiers during the Crimean War
  • Observed unsanitary conditions in the army hospital
  • Soldiers were dying of typhus, cholera, and dysentery instead of battle wounds.
  • Nightingale believed these infections were preventable.
28
Q

What are the complexities of disease transmission?

A

There are many factors associated with increased risk of diease transmission.

29
Q

What are the host characteristics that are associated is the factors of disease transmission?

A

Some Characteristics that are involved are:

  • Age
  • Sex
  • Reace and genetic factors
  • Immune status (decreased)
  • Nutritional status (lack)
  • Behavior (e.g. occupation, lifestlye, religion, customs)
  • Previous infection or current coinfections.
30
Q

What are the factors from the pathogen to cause disease?

A
  • Stability is the environment
  • virulence factors
  • Presence of immune evasion gnes
  • Resistance to antiviral therapy
  • Enhanced mode of transmission
31
Q

Within Modes of transmission:

What is direct?

What is indirect?

A

Direct: person to person

Indirect: Virus is transferred or carried.

32
Q

What is the Chain of infection?

How do you break the chain of infeciton?

A

Chain of infection: term frequently used in hospitals with regard to the control and prevention of infectious diseases.

Ways to break the chain:

  • Rapid ID of pathogen
  • Proper snitation
  • Disinfect or sterilize fomites
  • Barrier technique
  • handwashing
  • Proper trash and waste disposal
  • Proper food handling
  • Aseptic technique
  • Recognition of high risk individuals
33
Q

What is the concept of Herd immunity?

A

If the majority of population (herd) is mostly protected from a disease through immunization or genetic resistance, the chance of a major epidemic is unlikely.

When a population lacks herd immunity the disease spread very quickly or to many people

34
Q

What does an epidemiologist want to know?

A
  • Case definition (what)
  • Person (Who)
  • Place (where)
  • Time (when)
  • Risk factors (how and why)
35
Q

When gathering data…

What are descriptive studies?

What is analytical epidemiology?

A

Descriptive studies

  • Performed right after the epidemic occurs
  • Short study (e.g., Snow’s 1854 cholera study)
  • Published as case reports
  • Leads to lengthier, larger analytical studies

Analytical epidemiology

  • Determines the “why and how” of the epidemic
  • Hypothesis-driven studies
  • May involve control group
  • Cohort method (2 similar populations)
36
Q

Surveillance and serlogical epidemiology has several forms:

A
  • Monitor available data from mandated reports on reportable diseases
  • Active field surveillance at healthcare facilities
  • Serological screening of populations
  • antibodies are the “footprints” of disease exposure and protection against disease.
37
Q

A method of surveillance can be down with chicken. Describe the scenerio of the

Sentinel Chick Surveillance Program

A
  • Canadian health authorities used sentinel chickens along the Canadian/U.S. border to monitor for the presence of West Nile virus in 2000.
  • Chickens with West Nile develop a very short viremia without symptoms.
  • Scientists draw blood
  • looking for WNV antibodies.
38
Q

How are tracking diseases from outer space done?

A
  • Environmental factors play a role in outbreaks of viral illnesses.
  • Use of satellites to monitor changes on land surfaces.

——-Heavy rainfall (more mosquito eggs laid in standing water)

———Temperature changes

———Vegetation changes

39
Q

How are infectious diseases contained?

What is Quarantine?

A
  • Practice of quarantine is still used today to prevent person-to-person transmission of infectious diseases (e.g., SARS outbreak, tuberculosis)

Individual is thought to have been exposed to another individual suffering from a communicable disease
Animals too

  • Isolation: separation of ill individuals from healthy individuals
  • Placards
40
Q

What are things to consider while traveling?

A
  • What arthropod vectors are in the area?
  • Is there contaminated food or water (food and waterborne illnesses)?
  • What medical facilities exist in remote areas?
41
Q

What are some Medical facilities?

A
  • 15 percent of the population in rural Kenya is infected with HIV
  • Many live in districts with fewer than one doctor for every 15,000 patients
  • Clinics lack supplies, medicines, and expertise
  • Gov’t, religious groups, and private organizations provide support to remote areas of developing countries
  • Travelers should take active steps to minimize the risk of injury and infection
42
Q

Epidemiology Example: Nipah Virus

How was this virus come about?

A
  • Based on seroprevalence data and virus isolations, the primary reservoir for Nipah virus was identified as Pteropid fruit bats

Pteropus vampyrus (Large Flying Fox)

Pteropus hypomelanus (Small Flying-fox)

  • Overlap between bat habitats and piggeries in peninsular Malaysia

fruit orchards were in close proximity to the piggery

spillage of urine, feces and partially eaten fruit onto the pigs

43
Q

What is a Nipah Virus?

What is the structure?

How is it diagnosised?

What are the clinical features?

A
  • Negative strand ssRNA
  • Helical, enveloped

Diagnosis:

  • serum neutralization
  • ELISA
  • PCR
  • immunofluorescence assay
  • virus isolation by cell culture

Clinical features:

  • fever, migraine, vomiting, myalgia, and coma
  • case-fatality rate of 40%
44
Q

Continued Nipah Virus

Where and when did this virus come about?

A
  • Outbreak of febrile encephalitis in Malaysia in September 1998.
  • Initially thought to be Japanese encephalitis
  • Preceded by the occurrence of illness and excessive mortality in pigs in 3 pig-farming areas in same affected suburb
45
Q

Epidemiology Example: Nipah Virus

Who did it affect?

A
  • Ministry of Health Malaysia recorded a total of 283 cases of viral encephalitis with 109 deaths from 29 September 1998 to December 1999
  • 86% of case-patients reported touching or handling pigs before the onset of illness
  • Majority of patients were from 21 to 60 years of age (88.1%)
  • Largest number of cases (15.9%) occurred in the 40-44 year old age group, followed by the 30-34 and 25-29 age groups (13.8% and 13.1%, respectively)
46
Q

What is the prevention and control of the Nipah Virus?

A
  • Nationwide campaign to educate people on the dangers of JE and its mosquito vector

—-fogging of pesticides were carried out on 18,586 pig farms and 403,837 houses in the vicinity of the pig farms

  • Phase I: Immediate eradication by mass culling of pigs

—–1 million swine; significant impact pig industry in Malaysia

  • Phase II: Antibody surveillance of high-risk farms to prevent future epidemics
  • Additional actions: ban on transporting pigs within the country

—-No US imports from Malaysia during 1999 epidemic

47
Q

What are the fundamental Concepts?

A
  • Epidemiology is the branch of science that deals with how diseases affect groups (whole communities or populations).
  • —-Disease diagnostics,trends, prevention, and control measures
  • —Common terms
  • —-Pioneers in the field include Snow and Nightingale
  • Vaccination is an effective way to create herd immunity to prevent further spread of infectious disease
  • Two types of epidemiological investigations:
  1. Descriptive= provides the “what, when, where, and who” of an outbreak
  2. Analytical= provides the “why” and “how” of an outbreak
  • Surveillance programs and reporting systems play a fundamental role in public health
  • —Gov’t and private organizations
  • —Quarantine and isolation techniques
  • Medical clinics established globally to met the needs of travelers

—–Lack of proper supplies, medicines, and experienced staff

  • Changes in environment may set the stage for new diseases.
  • Nipah virus epidemiology

Virology (23 decks)

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