The occurrence of cases of an illness, specific health-related behavior, or other health-related events clearly in excess of normal expectancy. ( >Mean +2SD) The area and the period in which the cases occur are specified precisely
Adapted from WHO recommended surveillance standards, 2 nd edition, 1999
Judged to be an outbreak A greater number of cases than normally occur in the same place compare to the same period of time
Meningococcal Epidemic Curve July '96 - June '98, Ireland
Judged to be an outbreak A cluster of cases which can be linked to the same exposure. The number of meningococcal cases associated with pilgrims who have traveled for the Haj has increased, and the total number of cases to date is 14 including 4 death Judged to be an outbreak A single case of disease that has never been occurred . A 3 year old boy, case of Avian flu (HSN1), alerted the public health people around the world to start a full scale investigation
Estimate exposure period to calculate incubation period
No. Pt. Sick date (Point source outbreak) Min. IP Max. IP Median. IP 0 1 2 3 4 5 6 7 8 9 10
Compare Common Source Propagated source 1.Curve Bell curve Scatter bell 2.First and last pt. < 1 IP > 1 IP 3.Transmission One source From person to person 4.Duration Short Long 5. control Eradicate source Health education
Many adults in a remote village were sick with fever, severe joint and muscle pain and rash over the body
Is this an outbreak?
What is likely diagnosis?
Which intervention should be start?
Shall we start the investigation?
Measles, rubella, dengue
Shall we start vaccine or spray mosquitoes?
Outbreak confirmed, further investigation warranted Form outbreak Investigation & control team Epidemiologist Microbiologist Clinician Environmentalist Government Media etc. Team coordinates Field investigation
2. Define case and start case-finding 3. Descriptive data collection and analysis Descriptive epidemiology Person Place Time
Identify & count cases Obtain Information Identifying information Demographic data Clinical details Risk factors