Tutorial 1.pptx case definition in outbreak investigation

Case definition in outbreak investigation

1. Tutorial (1) Introduction to case definition

2. Objective By the end of this tutorial, students will be able to: Develop appropriate case definitions based on available outbreak data.

3. Class Agenda Introduction to Case Definitions (30 minutes) Definition and Importance of Case Definitions. Types of case definitions: Clinical, Epidemiological, and Laboratory. Group Activity: Developing Case Definitions (30 minutes) Divide students into small groups. Provide each group with a specific outbreak scenario with available data (e.g., measles outbreak in a school). Students will create case definitions for suspected, probable, and confirmed cases. Discussion and Presentation (20 minutes) Each group presents their case definitions. Class discusses similarities and differences across groups. Conclusion and Q&A (10 minutes) Summarize key points from the tutorial. Open floor for questions. Assessment Participation in group activities will be assessed. Students will submit their developed case definitions for feedback.

4. Introduction to Case Definitions

5. 1. Definition and Importance of Case Definitions Case Definitions are standardized criteria معايير موحدة used to identify and classify a particular disease, health condition, or event within a population. In the context of public health, a case definition outlines the specific set of symptoms, signs, and laboratory results that qualify an individual as having a particular condition , such as an infectious disease (e.g., COVID-19), chronic illness (e.g., diabetes), or other health events (e.g., food poisoning outbreaks).

6. Why Are Case Definitions Important? Consistency: Case definitions ensure uniform criteria for identifying and reporting cases, reducing confusion. Data Comparability: Standardized definitions allow for easy comparison of disease data across regions and globally. Public Health Monitoring: Help track disease spread, assess outbreak severity, and allocate resources efficiently. Diagnosis and Treatment: Guide doctors in accurately diagnosing and treating patients according to established guidelines. Outbreak Control: Enable experts to identify cases, monitor spread, and design control measures during outbreaks.

7. 2. Types of Case Definitions Case definitions are classified into three main categories , each serving a distinct role in the identification and reporting of diseases: Clinical case definition Epidemiological case definition Laboratory case definition

8. A. Clinical Case Definitions (suspected case) A clinical case definition is based on the symptoms and physical signs observed in a patient. It focuses on observable clinical criteria , such as the appearance of a rash, fever, or coughing. Example: Influenza’s clinical case definition may include fever, cough, sore throat, muscle aches , etc. Strengths: Useful when laboratory testing is unavailable or impractical. Allows for early identification of disease during an outbreak when testing capacities are limited. Limitations: Symptoms may be similar across different diseases, leading to potential misdiagnosis. Non-specific symptoms may lead to underreporting or overreporting of actual cases.

9. B. Epidemiological Case Definitions (probable case) An epidemiological case definition uses a broader context, incorporating not only clinical signs but also exposure history and known risk factors . Example: During a foodborne outbreak, an epidemiological case definition might include individuals who were present at a specific event where food contamination occurred, regardless of their clinical presentation. Strengths: Effective for identifying cases that may not yet show full clinical signs but were exposed to risk factors (e.g., contact with a confirmed case). Useful in outbreak investigations to track the source of disease spread. Limitations: Reliance on exposure data can sometimes be imprecise or unavailable, limiting the accuracy of the definition. May require more detailed investigation and resources for confirmation.

10. C. Laboratory Case Definitions (confirmed case) A laboratory case definition depends on the confirmation of a disease through diagnostic testing, such as blood tests, cultures, imaging , or genetic analysis . These definitions provide the highest level of certainty, as they rely on objective data obtained from laboratory examinations. Example: A laboratory case definition for HIV would involve testing for specific antibodies or viral RNA in the blood. Strengths: Provides the highest level of accuracy in diagnosing cases. Reduces the ambiguity of clinical symptoms or epidemiological risk factors. Limitations: Testing facilities may be limited, particularly in resource-poor settings or during large outbreaks. Laboratory delays can slow down diagnosis and reporting, especially in emergencies.

11. Activity: Case Scenario: Measles outbreak in a school By the end of this activity, students will: Understand the differences between suspected, probable, and confirmed case definitions. Learn to apply case definitions in various outbreak scenarios. Appreciate the importance of precise case definitions in managing disease outbreaks.

12. Scenario Description: A measles outbreak has been reported in a local elementary school. Over the past two weeks, several students have shown symptoms such as fever, cough, runny nose, and rash. The local health department is trying to contain the outbreak and has asked for assistance in defining cases of measles within the school to determine how widespread the outbreak is. The school serves about 500 students, ranging in age from 5 to 12 years. Most students are vaccinated, but several have exemptions due to medical or religious reasons. The outbreak seems to have started after a student who had recently traveled abroad returned to school while experiencing symptoms.

13. Category Student 1 (Age: 7, Female) Student 2 (Age: 9, Male) Student 3 (Age: 8, Female) Student 4 (Age: 6, Male) Student 5 (Age: 10, Female) Reported Symptoms Fever (38.89°C), cough, runny nose, red eyes, rash on face and neck Fever (38.61°C), cough, red eyes, rash on torso and arms Fever (37.11°C), rash on arms and legs, no cough Fever (38.33°C), cough, rash spreading from face to rest of body Rash on face and arms, no fever, no cough Laboratory Test Results Positive for measles IgM antibodies Lab results pending Not tested Lab results pending Negative for measles Epidemiological Data Traveled to a country with measles outbreak Same classroom as Student 1, close contact Classmate of Student 2, no known travel/contact with Student 1 Neighbor of Student 1, plays with Student 1 outside of school Sibling of Student 4, no other known exposure Vaccination Status Unvaccinated (religious exemption) Vaccinated with one dose of MMR Vaccinated with two doses of MMR Unvaccinated (medical exemption) Vaccinated with one dose of MMR Timeline of Symptoms Symptoms started 10 days ago (fever, cough, rash on day 3) Symptoms started 8 days ago (fever, rash on day 4) Symptoms started 7 days ago (fever, rash on day 2) Symptoms started 5 days ago (fever, rash on day 2) Symptoms started 2 days ago (rash only

14. Activity In this scenario, students would use the data provided to define suspected , probable , and confirmed cases based on: Symptoms, laboratory results, Epidemiological links, and Vaccination status.

15. Classification Student Symptoms Epidemiological Link Laboratory Confirmation Suspected Case Student 3 Fever (100.8°F), rash None No lab test performed Student 5 Rash on face and arms, no fever None Tested negative for measles Probable Case Student 2 Fever, rash, cough Close contact with Student 1 Lab results pending Student 4 Fever, rash Contact with Student 1 (neighbor) Lab results pending Confirmed Case Student 1 Fever, rash, cough None Positive for measles IgM antibodies

16. Activity 2: Mach the statement in column a with the suitable term (Sporadic, Endemic, Outbreak, Pandemic) COVI19 affects all countries of the world during the year 2020 Among 20 newborns, 2 cases was confirmed as neonatal tetanus in a rural hospital within a month During the year 2018, the reported number of typhoid patients in a country X is 50-70 / 1000 population while the reported cases in the previous year in the same country was 60 cases / 1000 population Few cases of influenza not related to each other are scattered all over the country