2. “A sudden rise in the incidence of a disease”
The occurrence in a community or region of cases of
an illness with a frequency clearly in excess of normal
expectancy.
3. Endemic infections in hospital
Usual or expected frequency of infections in the
hospital (background rate)
Epidemic nosocomial infections in hospital
Unusual occurrence of infections clearly in excess of
expected occurrence (background rate)
Isolation of unusual (rare) organism
Isolation of organism with different anti-microbial
susceptibility, or molecular typing
4. Common source epidemics
Single source or point source
Continuous or Multiple exposure
Propagated epidemics
Person to person spread
5. Outbreak in Hospital/ Health facility
Outbreak in Community
Outbreak in community may have origin in a hospital
Outbreak in community may trigger outbreak in hospital
We take almost similar steps to investigate community
and hospital outbreaks
Infection control programme in hospital may not only
prevent outbreak in hospital, but in community also
6. Prevent additional cases in the current outbreak
Prevent future outbreaks
Learn about a new disease
Learn something new about an old disease
Reassure the public
Minimize economic and social disruption
Teach epidemiology
7. Magnitude
Characterization of cases by time, person and place
Risk factors
Source of infection, mode of transmission
Control of outbreak
Prevent recurrence
Document the outbreak – lessons learnt
8. Epidemiologist
Clinician/paediatrician/ neonatologist
Microbiologist
Member of Hospital Infection Control Committee
Staff from affected unit/ward
Others depending on the need
9. Confirm the diagnosis
Confirm the existence of an outbreak
Define at-risk population and characterize the cases by
time, person and place (Case definition; case
ascertainment – identify and count cases; line list of
cases; epidemic curve)
Review of literature about outbreaks/isolates
Formulate hypothesis about genesis of outbreak
(source and route of infection)
Make further investigations to confirm/refute the
hypothesis (case control studies, culture surveys)
Control the outbreak
Prepare and disseminate the report (documentation)
10. Case definition changed
Introduction of new laboratory tests
Frequency of testing of patients changed
Introduction of a new medical or surgical
procedure
New areas or population included under the
surveillance
11. Confirm outbreak
– Confirm diagnoses
– Case definition
– Case line listing started
– Case finding
– Case interviews
– Complete line listing
– Case descriptive epidemiology
– Establish baseline occurrence of cases
– Rule out alternative explanations (chance, bias, ...)
Generate preliminary causal hypotheses
12. Standard set of criteria for deciding if a person should
be classified as suffering from the disease under
investigation.
Clinical criteria, restrictions of time, place, person
characteristics
Specific inclusion and exclusion criteria
Simple, practical, objective
Suspect, probable, confirmed
Case definition may be more sensitive initially
Case definition should be more specific when
sufficient information is available
13. Identification No.
Age
Sex
Date of admission
Cause of admission
Intervention/surgery/procedure done, device used, if any
Date of undertaking intervention/surgery/procedure
Place where intervention/surgery/procedure undertaken
Date of onset of outbreak associated clinical features
Outbreak associated clinical features
Lab investigations
Result of lab investigations
Diagnosis (Nosocomial infection)
Outcome: Still ill, recovered, died, other (specify)
Other relevant variables
Comments
15. • Who is at risk of becoming ill?
• What is the disease causing the
outbreak?
• What is the source and the vehicle?
• What is the mode of transmission?
Compare hypotheses with facts
16. Systematically review known causal factors
(Transmission mechanisms and dynamics)
Prioritize likely causes to guide control
measures (Step 3)
Generate testable hypotheses to conduct analytic study
(Step 4) if cause remains unknown or control measure
not working
19. Implement control measures
May occur at any time
during the outbreak!!
Control the source of infection
Interrupt transmission
Modify host response
Prevent recurrence
20. Control measures related to source of infection
Identify and remove the source of infection
Isolation of cases
Quarantine of healthy contacts of infectious disease
Interrupt transmission
Protect susceptible host
Immunization
Chemoprophylaxis
Non specific measures
Surveillance programme for detection/control of
infections
Risk communication (IEC)
Research
21. Prepare study protocol
1. Primary question(s)
2. Significance
3. Design
4. Subjects
5. Variables
6. Statistical issues
● Conduct study
● Analyze data
● Interpret findings
24. Detect outbreaks
Detect public health threats
Detect infectious cases (case finding)
Monitor trends in a target population
Monitor exposed individuals for symptoms
Monitor treated individuals for complications
Direct public health interventions
Evaluate public health interventions
Generate hypotheses for further evaluation
25. Communicate preliminary assessments and
recommendations (letter, memo)
Prepare interim/final reports
Prepare manuscript (optional)
Risk communication strategy (what to say)
Media communication strategy (how to say it)
26. Every outbreak in the
hospitals is an opportunity to
improve infection control
programme. Lessons learnt
should be used to prevent
future outbreaks
27. Assign a spokesperson who has the authority,
is knowledgeable and respected by community,
health professionals and media
Give clear, accurate and timely information. Avoid
technical terms, if possible. Update information
regularly.
Forward 3 positive points against one negative
point.
Do not allow media to control the entire
dialogue
Be frank about your efforts and the challenges
28. Chronology of events - How was the outbreak suspected?
Methodology adopted for investigation
Outbreak investigation Team
Case definition
Case ascertainment
Lab investigations
Epidemiological observations
Characterization of cases/deaths by time, person and place
Results of laboratory investigations
Analysis and interpretation of data collected and compiled
Further investigations undertaken
Conclusion about source and route of infection
Interventions made/recommended
Dissemination of report including executive summary to all
stakeholders
29. Viral hepatitis B outbreaks occurred in hospitals in 1980s
and 90s
In 1997, NICD investigated 3 community outbreaks of viral
hepatitis B
Mehasana district in Gujarat
Sirsa district in Haryana
Sri Ganganagar in Rajasthan
Inadequately sterilized needles and syringes resulted in
these outbreaks
Inadequate sterilization still causes many infectious
diseases outbreaks in hospitals
Source: WHO 1998; 76:93-98; Epidemiol Infect 2000;125:367-375
30. ESI Hospital Colony, Madurai had an explosive outbreak of
chikungunya in September 2009
Chikungunya cases were admitted to the ESI Hospital
There was heavy breeding of Aedes mosquitoes in the
campus
Infection was transmitted to other cases and hospital staff
9 of 11 doctors and 34 of 37 nurses who worked in the
hospital or stayed in the campus were affected during the
outbreak
Most of other residents of the hospital colony were also
affected
Hospital transmission of dengue and chikungunya has been
observed in other cities also in the past
31. A patient admitted in a hospital probably started
the outbreak
Infection spread to other patients, visitors and
health acre workers
66 probable cases, 45 died
Many including health care workers got infection
in the hospital
No exposure of cases to animals
Human to human transmission of Nipah/ Hendra
virus was suspected
Source: IJMR 2006;123: 553-560