community 3

Web of causation

Theorized that to fight a disease you have to identifyThe causes closest and break the web there

Epidemic

When disease exceeds normal frequency in a community - Ex) opioid epidemic

Pandemic

When epidemic spreads across the globe - Ex) covid 19, bubonic plague

Endemic

• Disease that settles in specific area

  • Ex) Malaria on Mali, plague in vietnam

Birthrate

• Total number of live births in 1 yr/mid year total population * 1000

Infant mortality rate

• specified geographic area dying under one year of age divided by the number of resident live births for the same geographic area (for a specified time period, usually a calendar year) and multiplied by 1,000.

 

Formula: (infant deaths in year/ live births in year)*1000

• Examples: 1,300 infant deaths in 2008 among state residents 150,000 live births in 2008

1,300/150,000 x 1,000 = 8.7 infant deaths per 1,000 live births in 2008 among state residents

Attack rate

• Number of people who got sick/number of people who got exposed*100

Morbidity rate

• Incidents of disease in population

 

Mortality rate

• Sum of deaths over time

• (Deaths in given time period * 10^n)/population risk

• Crude death rates = overall deaths

• Specific death rates = deaths from specific causes

• Case specific death rate =  deaths from specific disease

• Infant mortality rate= death rate of children under 1 for specific time period

  • (Infant deaths in year/live infant births in year) * 1000

 provide information about cause of death.

    Deaths in a given time period   X 1000

              population at risk

Epidemiological triad

• host

• Agent

• Environment

Host

• Human or animal that harbors agent

• Sex, age, genetics, FHx, Hx occupation, religion ,

• Can be less vulnerable- Inherit resistence

Agent

• Causes problem

  • Biologic

    • Bacteria, viruses

  • Chemical

    • Poison, alcohol, smoke

  • Physical

    • Trauma, radiation, fire

  • Nutritional

    • Lack, exess

  • Lack of white blood cells

• Vector

  • Carried the agent to the host

    • Mosquitos, ticks, sand fly

Environment

• Temperature, humidity, altitude

• Crowding, housing, neighborhood

• Water, milk, food

• Radiation, pollution, noise

 

• Geography, buildings, plants, insects

• Psychosocial influences influences

  • Poverty, lack of healthcare, stress factors at work

  • Psychology

  • Cultural

  • Social

  • Economic influences

Immunity

• Ability of a host to resist disease

Types:

• active

• Passive

• Cross immunity

• Herd immunity

Active immunity

• life long resistance to diseases.

  • Vaccines or infection experience

Passive immunity

• short term resistant naturally acquired or artificial

• antibodies

• Types

  • Naturally

    • Placental transfer IgG

    • Breast milk transfer IgA

  • Antibodies

    • Immunoglobulin injections (rabies, hep a, tetanus)

Cross immunity

• Resistance to one disease gives immunity to another

Herd immunity

• Population has immunity to disease

Four stages of disease

• susceptibility

• Preclinical stages

• Clinical disease

• Resolution

Susceptibility

• No one has been exposed yet but hosts and environment may display risk factors

• Risk factors like poor diet or genetics make them open to getting sick

Preclinical stage

• they have been exposed but aren’t showing symptoms.

• An incubation period may follow.

•  Induction or latency period  with non-infectious agents may last years-decades

Clinical disease

Signs and symptoms of the disease finally appear. This is when most people visit a doctor and get a diagnosis

Resolution

• The disease ends in Recovery, disability, or death with vaccination rate

 

Prevalence

• Amount of people who have particular health condition in population

• Rate:

  • Number of existing cases in the population at a specific time ÷ population total x 1,000 = _____ per 1,000

 

Incidence

Number of new cases in the population at a specific time

New cases ÷ population total x 1,000 = _____ per 1,000

sources of information for epidemiologic study

• Existing data

  • Vital statistics, census data, health agency disease reports

• Everyday informal observations

  • Diabetes cases

  • Abused children in clinic

Scientific studies

• Vital statistics

• Census data

• Reportable diseases

• Disease registries

• Surveillance systems 

• Environmental monitoring

• National Center for Health Statistics health surveys

• Federal public health agency reports

• Informal observational studies

• Scientific studies

• Counts