Infecious disease and Outbreak Flashcards
Outbreak Detection: How do you know an outbreak is occurring?
Typically first identified at the local level
- Report from doctor’s office, hospital, nursing home or laboratory
- Analysis of routine public health surveillance reports
- Analysis of “syndromic surveillance” reports
Why Investigate the outbreak?
- Primary motivation – prevent the spread of disease within initial population & prevent spread to additional populations
- Prevent future similar outbreaks
- Provide scientific explanation for the event
- React to and calm the public
Outbreak Investigation Steps
- Prepare and plan for the investigation
- Confirm the existence of an outbreak
- Identify and count cases
- Collect risk information
- Analyze data in terms of time, place, and person
- Collect specimens for laboratory analysis
- Institute control measures
- Formulate and test hypotheses
- Choose a study design
- Communicate the findings
What is line listings and what are included in it?
line listing is a method to quickly summarize pertinent variables. It is for Person information.
Each row represents a person. Each column represents a different variable
It should include:
- Identifying Information (name, address, phone number)
- Demographics (age, sex, race)
- Clinical information (symptoms, date of onset, laboratory results)
- Risk factor information (epi link to another case, food and other known exposures)
What is epidemic curve and 3 types of outbreak based on frequency?
Epidemic Curve depicts frequency of cases over time by plotting number of cases by date or time of onset. It is for time information.
- Point source epidemic – population exposed at one point in time.
- Common source epidemic – population continuously exposed.
- Propagated outbreak – involves person to person spread through population
Epi Curves – Point Source
Point source epidemics have a focal source that infects a number of people during a limited period of time. A good example would be a food handler. In point source epidemics the cases tend to occur during a span of time equal to the average incubation period of the disease.
Epi Curves – Common Source
The source is prolonged over an extended period of time and may occur over more than one incubation period.
Epi Curves – Propagated Outbreak
In a propagated epidemic an initial cluster of cases serves as a source of infection for subsequent cases and those subsequent cases, in turn, serve as sources for later cases. This can result in a series of successively larger peaks, reflective of the increasing number of cases caused by person-to-person contact, until the pool of susceptible people is exhausted or control measures are implemented.
Calculating attack rates and attack rate ratios with line listing
attack rate = Number of new cases/ population at risk
attack rate ratios = RR
Epidemiologic Triangle
In infectious disease epidemiology, there are numerous determinants that influence the susceptibility to and the development of disease.
The Epidemiologic Triangle is a framework for organizing these determinants and emphasizes the interrelation between three components: Host / Agent / Environment. (sometimes Vector at the center too)
Epi Triangle Example
•Host – Female •Agent – Influenza •Environment – Nursing home
Example of host factors
age
gender
diet and nutrition
ethnicity
Example of agent factor
size
motility
requirements for replication
Example of environment factors
physical
biologic
cultural
Example of vector factor
Life span
habitat
feeding practices
