BMS1042 Lecture Notes - Lecture 13: Mycobacterium Tuberculosis, Human Microbiota, Relative Risk
20 Jun 2018
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Department
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Professor
COMMUNICABLE DISEASE
The control and eradication of communicable diseases remains a global priority. In these weeks
you will learn about regional and global aspects of infectious diseases, particularly their social
and ecological determinants, emergence and burden. Over the next two weeks you will learn
what are the methods used in contemporary public health practice and applied in
population-based prevention and control of diseases such as sexually transmissible infections,
blood borne viruses and enteric infections. You will engage in discussions about prevention and
participate in an outbreak investigation exercises
13. THE WALKING DEAD OUTBREAK INVESTIGATION
An understanding of specific outbreak investigation terminology
An outbreak (or epidemic) exists when there are more cases than expected of a particular
disease among a specific group of people in a given area, over a particular period of time.
Epidemic
: More cases than usual
Outbreak
: Same as epidemic
Pandemic
: Worldwide epidemic
Cluster:
Group of cases
Endemic:
Permanent disease incidence (base-line)
Ability to describe barriers to care and outbreak control
- How to manage critically ill patients
- Build good-will in the community to eliminate distrust
- How to help patients who live in remote settings with limited resources
1. Identify the pathogen/ source of infection
2. Control and stop new cases
3. Prevent future outbreaks
As a bonus, we can learn about the disease and provide training opportunities.
To identify the preventive steps and strategies taken in an outbreak investigation
1. Prepare for field work: First we need good epidemiological knowledge on the outbreak.
What are the usual risk factors? Have there been previous outbreaks? Then we need to
gather supplies and equipment, and make sure we have a competent lab, with portable
devices. Team and administrative composition needs to be thought out.
2. Verify the existence of the outbreak: An outbreak is defined as “more than usual”, but
what is “usual”? To work out the baseline incidence, we have to look at the community,
region, and time period precisely (person, time, place). A way we do this is precise
surveillance, which involves monitoring of diseases in populations. It’s important to note
that false alarms may exist when there is a change in policy, a change in case definition,
increased public awareness, or increased reporting.
3. Confirm the diagnosis: Review the clinical findings and lab results. Be as specific as
possible about causative agent.
4. Define and identify cases: Use healthcare facilities, labs, and alert the public so they
can identify themselves
5. Describe the data (person, place, time):Draw an epidemic curve (number of cases (y),
time (x)), map the data, and explore data according to personal characteristics.
Common point source Continuous extended Propagated/ progressive
6. Develop hypotheses
7. Evaluate hypotheses
8. Refine hypothesis / perform additional studies
9. Implement control and prevention measures: Once the source of outbreak has been
identified, the aim becomes to break the links in the chain of infection.
10. Communicate findings: This needs to occur throughout the entire outbreak
investigation to ensure everyone remains calm and we can subside fear as best as we
can. Clearly state the facts, and beware of legal implications.
14. MEASURING RISK OF OUTCOME AMONG EXPOSURES
GAME PLAN
Understand the difference between probability and odds.
Probability = event of interest/ (all events) OR success/ (success + failures)
Odds = Event of interest/ not event of interest OR success/ failures
Understand the difference between and calculate relative risk (RR) and odds ratio (OR).
Both RR and OR is used to quantify the risk of an outcome of interest in the exposed group,
compared to the unexposed group. RR is the probability of an event occurring to an exposed
group compared with the unexposed group. OR is the odds of exposure in cases compared with
controls.
Ability to interpret and apply RR and OR values in the appropriate study design context.
Calculation of Standard Error (SE), 95% Confidence Interval (CI) and p-value of RR/OR.
Calculating RR
Document Summary
The control and eradication of communicable diseases remains a global priority. In these weeks you will learn about regional and global aspects of infectious diseases, particularly their social and ecological determinants, emergence and burden. Over the next two weeks you will learn what are the methods used in contemporary public health practice and applied in population-based prevention and control of diseases such as sexually transmissible infections, blood borne viruses and enteric infections. You will engage in discussions about prevention and participate in an outbreak investigation exercises: the walking dead outbreak investigation. An outbreak (or epidemic) exists when there are more cases than expected of a particular disease among a specific group of people in a given area, over a particular period of time. Ability to describe barriers to care and outbreak control. Build good-will in the community to eliminate distrust. How to help patients who live in remote settings with limited resources.
