lecture 16 - Lecture Goals Lecture 16 Infectious Disease...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Lecture 16 Infectious Disease Epidemiology II Lecture Goals { Discuss steps to follow when investigating an outbreak and describe what each step entails { Draw epicurves for different modes of transmission { Calculate primary and secondary attack rates Definitions { Endemic – background cases; expected number of cases { Epidemic – excess number of cases in a localized area { Pandemic – excess number of cases worldwide Levels of Disease 0 5 10 15 20 25 30 TIME CASES Epidemic Endemic A pandemic occurs because… ± Entire populations are susceptible ± There are no effective treatments for the outbreak Types of Epidemics
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Defining an Outbreak { An outbreak occurs when there are more cases than you’d expect in a given area or among a given population in a specific period of time Steps to Investigating an Outbreak 1. Verify the outbreak 2. Plot an epidemic curve 3. Calculate attack rates 4. Determine the source of the outbreak 5. Recommend and implement control measures #1: Verify the Outbreak { Establish a case definition z Who (person) z What (symptoms) z Where (place) z When (time) { Identify, confirm, and quantify cases { Determine if there more cases than expected Types of Cases { Index Case – first person that is sick { Primary Case – people who get sick from being directly exposed to the agent { Measured by attack rate { Secondary Case – people who get sick from being exposed to a primary case { Measured by secondary attack rate #2: Plot an Epidemic Curve { Graph the cases { x-axis = time of onset { y-axis = # of cases { Interpret the curve z Describe pattern z Determine incubation period and perhaps mode of transmission { Examine Outliers Point Source Transmission { Most common type of food-borne outbreak { Large population with a short exposure period { Easier to identify incubation period { Example: Bad potato salad at a picnic # Cases Time
Background image of page 2
3 Salmonellosis in passengers on a flight from London to the United States, by time of onset, March 13--14, 1984 Source: Investigating an Outbreak, CDC Continuing Source Transmission { Several peaks of cases { Difficult to characterize incubation period { Example: Refrigeration temperature is off all week in a restaurant Time # Cases Vector-borne Disease { Cases start slowly { Incubation period estimated by time between first case and the peak of cases { Cases taper off slowly { Example: West Nile # Cases Time #3: Calculate Attack Rates { An incidence rate { Expressed as a percentage Attack Rate = # Ill * 100 Ill + Well { Calculated for different exposures or settings { Calculate RR – compare Attack Rates for exposed vs.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/06/2008 for the course PUBLIC HEA 832:335 taught by Professor Schneider during the Spring '08 term at Rutgers.

Page1 / 8

lecture 16 - Lecture Goals Lecture 16 Infectious Disease...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online