1. Outbreak Investigations
CHS 446
Communication Skills for the
Healthcare Professional
Mohammed S. Alnaif, Ph.D.
6/10/2018
Dr. Mohammed Alnaif

2. Outbreak Investigations
Epidemic refers to the outbreak of a disease in a localized group of people; it can be infectious and spread from one person to another.
Epidemic nosocomial infections are defined as hospital-acquired infections that represent an increase in incidence over expected rates.
6/10/2018
Dr. Mohammed Alnaif

3. Outbreak Investigations
Outbreaks: The basics
Goals of an outbreak investigation:
To identify the source of illness
To guide public health intervention
Ways to recognize an outbreak:
Routine surveillance activities
Reports from clinicians and laboratories
Reports from affected individuals
6/10/2018
Dr. Mohammed Alnaif

4. Outbreak Investigations
Epidemic associated infections usually are clustered temporally or geographically, suggesting that infections are from common source or are secondary to increased person-to-person transmission.
These outbreaks are often associated with specific procedures or devices.
6/10/2018
Dr. Mohammed Alnaif

5. Outbreak Investigations
Epidemics are important because they account for substantial percentage of nosocomial infections.
Approximately 5% of nosocomial infections occur in epidemics.
Most of these infections occur in small clusters of two to three patients.
6/10/2018
Dr. Mohammed Alnaif

6. Outbreak Investigations
If infection control personnel thoroughly investigate nosocomial epidemics, they may identify new agents, reservoir, or mode of transmission.
To accomplish these goals, infection control personnel must evaluate data obtained from epidemiologic studies and from microbiologic and molecular studies.
6/10/2018
Dr. Mohammed Alnaif

7. Outbreak Investigations
Recognizing Outbreaks
Epidemiology determines questions to ask
Laboratory provides answers
EPI and LAB together “solve” most outbreaks (especially true for outbreaks in healthcare facilities)
6/10/2018
Dr. Mohammed Alnaif

8. Outbreak Investigations
Surveillance
cultures
Environmental
samples
Culture ID
Susceptibility
testing
Isolate typing
Surveillance
Provides first evidence of outbreak
Often detected by microbiology
Line list of cases
Epi-curves
Case-Control study
Exposure risks
Epidemiologic Studies
A hospital outbreak usually begins when ongoing surveillance signals a clusters of unusual infections.
ADVANCE
This provides the first evidence of an outbreak, and is often picked up by the microbiology lab.
Epidemiologist in the field then help define the outbreak by providing a line-list of cases, an epi-curve which shows the distribution of cases over time, and perhaps results of a case-control study, which can give clues to exposures that are related to the disease in question.
But it usually work done in the laboratory that confirms the suspicions raised by epidemiology. This may involve:
collection of surveillance cultures to see if the outbreak is ongoing,
collection and identification of environmental samples and clinical isolates,
susceptibility testing of organisms and molecular typing to see if they are related.
Many hospital outbreaks end once the organism and its transmission dynamics have been determined. This usually results in local interventions such as isolation of patients, a change in disinfection protocol, or even suspension of an implicated procedure or closure of a unit until new cases cease to arise.
Confirmatory Studies
Patient isolation
Enhanced disinfection
Suspend procedure or
close unit
Local Interventions
Adapted from Ostrowsky and Jarvis Efficient Management of Outbreak Investigations

9. Outbreak Investigations
Recognizing Outbreaks
Hospitals must have reliable, sensitive surveillance systems that allow the infection control personnel to detect increased infection rates in a defined time period and geographic area, suggestive of epidemic transmission.
Sometimes outbreaks are easy to recognize.
6/10/2018
Dr. Mohammed Alnaif

10. Outbreak Investigations
Recognizing Outbreaks
Sometimes outbreaks are easy to recognize.
Fore example, even one episode of an uncommon infection, such as group A streptococcal surgical site infection, can indicate an out break.
6/10/2018
Dr. Mohammed Alnaif

11. Outbreak Investigations
Recognizing Outbreaks
Sometimes outbreaks are easy to recognize.
In other cases, an increased incidence of infection caused by unusual organisms, such as multidrug-resistant Mycobacterium tuberculosis, indicate epidemic transmission.
6/10/2018
Dr. Mohammed Alnaif

12. Outbreak Investigations
Steps in Outbreak Investigation
Preliminary Investigation and descriptive Study
Review existing information
Determine the nature, location, and severity of the disease problem
Verify the diagnosis
Establish a case definition
Find and ascertain case-patients.
6/10/2018
Dr. Mohammed Alnaif

13. Outbreak Investigations
Steps in Outbreak Investigation
Preliminary Investigation and descriptive Study
Request that the laboratory save isolates from affected patients and from suspected sources or vehicles
Draw an epidemic curve
Summarize data in a line-listing
Establish the existence of an outbreak
Institute or assess adequacy of emergency control measures.
6/10/2018
Dr. Mohammed Alnaif

14. Outbreak Investigations
Steps in Outbreak Investigation
Comparative Study and Definitive Investigation
Review records of existing case-patients
Develop hypotheses
Test hypotheses in comparative (case-control or cohort) studies
Conduct microbiologic or other laboratory studies and surveys
Conduct additional studies, including observational studies, surveys, or experiments, to confirm the mode of transmission
6/10/2018
Dr. Mohammed Alnaif

15. Outbreak Investigations
Emergency Measures
Once the outbreak is confirmed we decide immediately whether to:
Conduct a full epidemiological study
Obtain cultures from equipment or suspected vehicles
Call local, or central agencies
Institute emergency control measures
6/10/2018
Dr. Mohammed Alnaif

16. Outbreak Investigations
Emergency Measures
When making these decisions we should consider the following factors:
The mortality associated with the epidemic
The public health importance of the outbreak
The frequency of infection versus colonization
The possibility of a common source
The size of the outbreak
The characteristics of the pathogen
Local and government regulation that may require healthcare facilities to report epidemics
6/10/2018
Dr. Mohammed Alnaif

17. Outbreak Investigations
Closing the Ward
The epidemiology staff must weight carefully the benefits of closing a ward or a unit against the risk of decreased access to care.
6/10/2018
Dr. Mohammed Alnaif

18. Outbreak Investigations
Reporting Outbreaks
Epidemiology ICP should report to the local health officials all outbreaks that have potential public health implications at the local or national level.
6/10/2018
Dr. Mohammed Alnaif

19. Outbreak Investigations
Reporting Outbreaks
In addition, ICP should report suspected intrinsic contaminations, infections caused by contaminated blood transfusion reactions, infections associated with defective devices to the hospital infections programs, and local health officials.
6/10/2018
Dr. Mohammed Alnaif

20. Outbreak Investigations
Conducting an Epidemiologic Study
Reviewing the Line-Listing
Before conducting a comprehensive epidemiologic study, ICP should review line- listing and the epidemic curve, because these tools may suggest the cause of the outbreak.
6/10/2018
Dr. Mohammed Alnaif

21. Outbreak Investigations
Comparative Studies
In many outbreaks, a putative risk factor can be confirmed only if it meets certain criteria.
First the risk factor must have been present before the onset of the disease.
Second the risk factor generally will be associated with the condition statistically.
6/10/2018
Dr. Mohammed Alnaif

22. Outbreak Investigations
Comparative Studies
To confirm the second point, epidemiology staff must either compare affected patients with patients who did not acquire the condition (control) or compare the rate of the condition among patients with certain putative risk factor to the rate among patients without the risk factors (a cohort study).
6/10/2018
Dr. Mohammed Alnaif

23. Outbreak Investigations
Observational Studies
ICP should observe health care workers perform procedures, particularly patient-care techniques that might be related to outbreaks.
6/10/2018
Dr. Mohammed Alnaif

24. Chapter 14 Outbreak Investigations
Culture Surveys
Organisms that cause nosocomial outbreaks can be isolated frequently from nonsterile environmental sources or from staff.
6/10/2018
Dr. Mohammed Alnaif

25. Chapter 14 Outbreak Investigations
Demonstrating Biological Plausibility
The investigators should design and conduct additional studies to confirm that the reservoir and the mode of transmission are biologically plausible.
6/10/2018
Dr. Mohammed Alnaif

26. Chapter 14 Outbreak Investigations
Acting on Results
ICP should focus their interventions on the immediate cause of an outbreak and should institute the simplest measures that will correct the problem.
ICP should develop a plan and timeline for implementing the control measures.
ICP must determine whether the measures are effective.
6/10/2018
Dr. Mohammed Alnaif

27. THANK YOU
6/10/2018
Dr. Mohammed Alnaif