Class 2- Outbreak Response Flashcards
Elements of the Course of Infection
- The incubation period
- The latent period
- The infectious period
The incubation period
The time between infection with a disease and the development of symptoms. Dictates when cases will be detected relative to individuals’ time of infection.
The latent period
the time between when an individual is infected and when he or she becomes infectious. May be the same about of time as the incubation period.
The infectious period
How long is a disease infectious to others?
Force of infection
the rate at which susceptible individuals acquire infection at a particular time, regardless of the source.
Force of infection= βI
Key components of analytic studies
- Exposure Assessment
- Determining the link between exposure (i.e. exposed and unexposed) and outcome of interest.
- Exposures can be fixed in an individual (genetics) or vary over time (seasonal flu)
- Outcome Assessment
- At the end of the period of risk, individuals will be in one of two groups
- infected or not infected
- Epidemiology is interested in the rate people move from exposure to outcome.
- At the end of the period of risk, individuals will be in one of two groups
Steps of Outbreak investigation
Step 1. Detect a possible outbreak
Step 2. Find and define cases
Step 3. Investigate cause
Step 4. Conduct analytic study
Step 5. Control measures
Step 6. Conclusions
Step 7. Plans for continued surveillance
Outbreak Investigation Step 1: Detecting a possible outbreak
Health surveillance systems are in place to monitor for abnormal trends in disease transmission Informal reports
- Reports from the community of spreading illness Formal reports
- Provided by doctors/microbiologist who observe an increase in cases for pathogen x.
- Tip of the iceberg – what about cases not showing up at health centers?
- Often, the first illnesses that are recognized are only a small part of the total outbreak.
- Identify cases, population at risk, and controls
Outbreak Investigation Step 2: Find and define cases
Conduct interviews with questions pertaining to:
- Signs and symptoms
- Onset of symptoms
- When did symptoms stop?
- Sample collection?
- Respond to Rx (if applicable)
- Prior behaviors
- Demographics
- Potential exposures
- There might be several case definitions for an outbreak investigation, each with a different purpose.
- For example, one case definition might be for confirmed illnesses and another for probable illnesses. Understanding transmission mechanisms will assist in confirming the causative agent of interest and source of exposure.
- There might be several case definitions for an outbreak investigation, each with a different purpose.
Case count
The number of illnesses that meet the case definition Are there secondary cases?
- Causative agent may be transmissible from person to person
Outbreak Investigation Step 3: Cause investigation
Identify common sources of exposure based on interviews, health reports, time lines
Cases can be both suspected or confirmed
Generate hypothesis about exposure
Determine probable route of exposure
- Routes of exposure?
Component of pathogen discovery
- Do you now have enough information to determine the pathogen?
Outbreak Investigation Step 4: Conduct analytic study
Choosing the correct study design
Determining the correct lab methods
- By now you should hopefully have an idea of what pathogen you are dealing with:
- Water/food/air/vector borne
- bacteria/virus/parasite/prion
What additional tests (measurements) are needed to test sources of exposure
What type of outbreak are you looking at?
- Point source
- Continuous
- Cluster
- Propagated
Frequencies of exposure to certain sources
Dose response relationships
What is the dose response relationship?
Magnitude, duration, and frequency of exposure
- i.e. 1 slice of contaminated cake vs a whole cake
- Eaten immediately vs. eaten slowly over the course of a week
- 1 slice vs 1 slice a day
Types of outbreaks
- Point source
- Continuous
- Cluster
- Propagated
Outbreak Response Step 5: Control measures
Initiating public health interventions
Monitoring and isolating infectious cases
Closing of area of source exposure
Communicating to the public ways to prevent infection
Examples of control measures:
- Spraying for mosquitoes
- decontaminating water supplies
- offering screening
- providing early treatment
- rodent control
- removal of vegetation
- animal culling
- vaccination programs
- mass drug administrations
- food recalls
- Methods used vary by outbreak
Outbreak Response Step 6: Dissemination of information to the public and stakeholders
How do you know an outbreak is over?
Are there any social/economic ramifications to this outbreak?
- Communicating with tact
- Avoiding hysteria
- Know your audience
- Speaking with clarity and it terms the community would understand vs. scientific reporting to agency stake holders
What lessons were learned from your outbreak scenario?
Do surveillance and response protocols need to be re-evaluated?
Outbreak Response Step 7: Plan for continued surveillance
If this is a new pathogen in the community, are plans being set in motion to monitor for the disease?
- See ebola in Dallas
Do health care providers need additional education on this subject?
Are there more efficient ways to conduct surveillance?
Chain of Infection
- Reservoirs maintain the agent
- Mode of transmission is how the agent moves from the reservoir to a host.
- Portal of entry=route of exposure
What is individual prevention
What can “you” do to prevent outbreak
What is community prevention
What groups/organizations can do to prevent outbreak
Individual Prevention Measures
- Hand washing
- Food safety
- Male condoms
- Personal prevention measures against vector-borne diseases
- Avoidance and elimination
- Physical barriers
- Chemical barriers
- Other barriers
- Chemoprophylaxis
Personal prevention measures against vector-borne diseases:
- Avoidance and elimination
- Physical barriers
- Chemical barriers
- Other barriers
- Chemoprophylaxis
Community Prevention Measures
- Sanitation and water safety Isolation, quarantine, case finding, and contact tracing
- Screening of the blood supply
- Community prevention measures against vector-borne diseases
- Environmental management
- Larval control
- Chemotherapy
- Insecticide-treated bednets
- Indoor residual spraying
