University:
American Career College
Course:
NURS115 | Intermediate Medical
Academic year:

2020
Views:

164

Pages:

18
Author:

Opfer8fg

10 Outbreak Investigation Disease Outbreaks 11 ¨ If an outbreak occurs in the group of people who have eaten the food, it is called a common- vehicle exposure, The food may be served only once: single exposure ¤ served more than once: multiple ¤ ¨ When a water supply is contaminated with sewage because of leaky pipes, Periodic: due to changing pressures in the water supply system ¤ Continuous: constant leak leads and persistent contamination ¤ Incubation periods for 191 delegates affected by a Salmonella typhimurium outbreak at a medical conference in Wales, 1986. 12 Epidemic curve of all confirmed global cases of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) 13 14 The three critical variables in investigating an outbreak or epidemic 1. 2. 3. When did the exposure take place? When did the disease begin? What was the incubation period for the disease? If we know any two of these, we can calculate the third. Exploring Occurrence of Disease Investigation 15 ¨ ¨ ¨ WHO WHEN WHERE Attack rate 16 food-specific attack rate 17 CROSS-TABULATION 18 ¨ ¨ several possible causal agents, To determine which of the possible agents is suspected to be the cause Attack Rate 19 ¨ In general, time is not explicitly specified in an attack rate ¤ ¤ ¨ ¨ ¨ ¨ the exposure is common the illness is acute A person who acquires the disease from that exposure is called a primary case. A person who acquires the disease from exposure to a primary case is called a secondary case. The secondary attack rate is defined as the attack rate in susceptible people who were not exposed to the suspected agent who have been exposed to a primary case. It is a measure of person-to-person spread of disease after the disease has been introduced into a population STEPS IN INVESTIGATING AN ACUTE OUTBREAK 20 1. 2. 3. 4. 5. 6. 7. 8. Define the outbreak and validate the existence of an outbreak Examine the distribution of cases Look for combinations (interactions) of relevant variables Develop hypotheses Test hypotheses Recommend control measures Prepare a written report of the investigation and the findings Communicate findings to those involved in policy development and implementation and to the public 21 Define the outbreak and validate the existence of an outbreak ¨ a. Define the “numerator” (cases) Clinical features: Is the disease known? ¤ What are its serologic or cultural aspects? ¤ Are the causes partially understood? ¤ ¨ ¨ ¨ Define the “denominator”: What is the population at risk of developing disease (i.e., susceptible)? Determine whether the observed number of cases clearly exceeds the expected number Calculate the attack rates Examine the distribution of cases 22 ¨ ¨ ¨ Time Place Time-place interaction Develop hypotheses 23 ¨ based on: a. Existing knowledge (if any) of the disease ¤ b. Analogy to diseases of known etiology ¤ c. Findings from investigation of the outbreak ¤ Test hypotheses 24 ¨ ¨ a. Further analyze existing data (case-control studies) b. Refine hypotheses and collect additional data needed Recommend control measures 25 ¨ ¨ a. Control of current outbreak b. Prevention of future similar outbreaks Outbreak 26 Outbreak- 2 foods 27