Outbreak investigation

===Lecture Details===
A Lecturer; Week 9 MED1022; Epidemiology
===Lecture Content===
Outbreak or epidemic is when there is more cases than expected of a particular disease among a given group of people in a given area over a given amount of time. An epidemic- more cases than usual; outbreak- same as an epidemic; pandemic- worldwide epidemic, a cluster- group/aggregation of cases, an endemic- permanent/regular disease incidence
Outbreaks occur due to new appearance of infectious agent or toxic material, arrival of susceptibles to environment with endemic pathogen, introduction of effective route of transmission from source to susceptibles e.g. climate change and mosquitoes
Steps of outbreak investigation: 1. prepare for field work : Epidemiological knowledge, supplies and equipment, team composition, administrative, personal
2. verify existence of outbreak: Defined as more cases than usual, establish usual, surveillance, can be false alarms which require health policy changes
3. confirm diagnosis: Review clinical findings, review laboratory results of cases, be as specific as possible about causative agent, talk to cases
4. define and identify cases: Case definition is important and may change, sensitive vs. specific, divide into confirmed, probable, possible, case finding is important
5. describe and orient data: Time, place, person
Epi curves: common point source, steep upslope and gradual downslope; continuous extensed source epidemics has a sharp up-swing followed by a plateau that corresponds to duration of exposure, then a right tail; propagated or progressive outbreak has progressively taller peaks which are one incubation period apart
6. develop hypotheses: Case control or cohort study, odds ratio
7. evaluate hypotheses; 8. refine hypotheses/perform additional studies
9. implement control and prevention measures ASAP, aim to break links in chain of infection, do as soon as possible
10. communicate findings: Throughout outbreak investigation, prepare timely reports, clearly state facts, beware of legal implications, aim to improve practice
===Readings===