outbreak investigation.pdf

Outbreak investigation (Infection control) Dr. Mais Alkhalili Community medicine Specialist What is an outbreak? The occurrence of more cases of a disease than expected for a particular place and time No. Cases of a Disease...

Outbreak investigation (Infection control) Dr. Mais Alkhalili Community medicine Specialist What is an outbreak? The occurrence of more cases of a disease than expected for a particular place and time No. Cases of a Disease “More than expected” = “Outbreak” “Usual”, “Expected” Time How potential outbreaks are identified Review of surveillance data Clinician or laboratory reports of unusual diagnoses Reports from the public Reports from the media Objectives of a field investigation Identify the: agent source, and/or mode of transmission Characterize the extent of the outbreak, e.g., who has been affected, who is at risk Identify exposures or risk factors that increase risk of disease Develop and implement control and prevention measures  Steps of an Outbreak Investigation 5 General phases of an outbreak investigation Descriptive Explanatory Response Descriptive phase 1. Prepare for fieldwork Done 2. Confirm existence of an outbreak simultaneously 3. Verify the diagnosis or in any order 4. Construct a case definition 5. Find cases systematically and record information 6. Perform descriptive epidemiology Explanatory phase 7. Develop hypotheses 8. Evaluate hypotheses epidemiologically 9. Reconcile epidemiology with laboratory and environmental findings 10. Conduct additional studies as necessary Response phase 11. Implement and evaluate prevention and control measures 12. Initiate or maintain surveillance 13. Communicate findings Components of an outbreak field investigation Epidemiology Laboratory Environmental Outbreak case definitions are commonly constructed using the following elements: 1. Clinical criteria based on: Clinical symptoms and signs that are characteristic of the disease of interest Laboratory tests, both microbiological and clinical 2. Epidemiological criteria (especially for outbreaks) that specify time, Place, Person When developing a case definition, you must be as precise as possible in the language that is used, because other people will use the case definition, and you want everyone to make the same decision in the same way about whether a patient meets the case definition or not.  The criteria should be: Objective, Simple, Accurate, Practical, and Measurable where possible. The following case definition applies to COVID-19 based on clinical criteria, epidemiologic criteria, and laboratory testing. Clinical Criteria: Acute Respiratory Illness: 1. Fever (subjective or confirmed) 2. Cough 3. Shortness of breath 4. Additional symptoms may include fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea. Laboratory Criteria: Confirmatory Laboratory Evidence: Detection of SARS-CoV-2 RNA by a molecular amplification test (e.g., RT-PCR). Epidemiologic Criteria: 1. Being within 6 feet for at least 15 minutes over a 24-hour period with a confirmed or probable case of COVID-19. 2. Direct physical contact with a confirmed or probable case. 3. Providing care at home to someone who is sick with COVID-19. 4. Direct contact with infectious secretions (e.g., being coughed on). Case classification levels laboratory confirmed, Confirmed compatible symptoms compatible symptoms, Probable epidemiologically linked Possible or Suspect compatible symptoms What is a hypothesis? Hypothesis (in context of outbreak) = educated guess about an association between an exposure and outcome, and/or about mode of spread Hypothesis should be in a form that allows it to be tested  Knowledge of the disease, its reservoir, it’s mode of transmission, and other features is probably the most common way of developing hypotheses. For a disease without a confirmed diagnosis yet, ask yourself what kinds of agents can cause this clinical presentation? What kind of agents usually cause this clinical presentation? For a known disease but unknown source or reservoir or vehicle, ask, What are the agent’s usual reservoirs? How is the agent usually transmitted? What are the most common vehicles for transmitting this agent to humans? What are the known risk factors? What are the usual suspects for this disease? e.g., for cholera – water For measles – contact with a case  We spent a lot of time reviewing descriptive epidemiology. One of the reasons descriptive epidemiology is so important is that it provides clues that we can use to develop hypotheses. Time (Epidemic curve) -- Does the shape hint at the mode of transmission? Does the narrow peak point to a particular time of exposure? Place – Are attack rates particularly high in one area? What is special about that place (neighborhood, wing of hospital, etc.)? Person – Which group(s) — by age, sex, occupation, etc. — have the highest rates? In some cases, when combining the laboratory, clinical, environmental and /or epidemiological evidence, the evidence is strong enough to determine the association without further testing. For example, if the newborns in the meningitis example tested positive for Neisseria meningitides, and staff, mothers, and visitors were tested and only 1 visitor tested positive for Neisseria meningitides, and that visitor was around all of the babies who tested positive, you may not need to conduct an epidemiologic study. Evaluating hypotheses: Conduct analytic study Comparing hypotheses with collected evidence Laboratory evidence Clinical evidence Environmental evidence Epidemiologic evidence Conduct analytic study – cohort study – case-control study However, if the evidence isn’t as strong, or if there is some question as to the cause, analytic epidemiology is used to test if an association exists, and if so, how strong it is. The most common types of analytic studies used in outbreak investigations are cohort studies and case-control studies Implementing control measures Prevent further exposure and future outbreaks by eliminating or treating the source Initiate as soon as possible Control strategies Reservoir Route of Susceptible Host Transmission Agent Control the Interrupt Protect reservoir transmission the host Prevention and control measures Immediate control measures Working with persons at risk Long-term control measures Working with regulators or government Long-term response Why did the outbreak occur? Do these conditions still exist, i.e., could another outbreak occur again? What is needed to change the conditions and reduce possibility of future outbreak? Education? Sanitation improvement / inspection? Vaccination? Legislation? Other? hospital-acquired infections outbreak Steps for investigating cases of hospital-acquired infections or a suspected outbreak Outbreak investigations in a hospital are critical for identifying, controlling, and preventing infectious disease outbreaks. Here are the key steps involved in such an investigation: 1. Preparation Develop a Plan: Create a response plan detailing roles, responsibilities, and communication strategies. Assemble a Team: Form an investigation team including epidemiologists, infection control practitioners, laboratory personnel, and other relevant experts. 2. Detection of an Outbreak Identify the Problem: Recognize unusual patterns in the incidence of disease. This could be through routine surveillance, reports from healthcare workers, or patient complaints. Confirm the Outbreak: Ensure the increase in cases is real and not due to changes in reporting, diagnostics, or population at risk. 3. Case Definition and Finding Cases Develop a Case Definition: Create a standard set of criteria for identifying cases, including clinical symptoms, lab results, and exposure history. Case Finding: Search for cases through active surveillance, reviewing medical records, and interviewing staff and patients. Outbreak investigations in hospitals are complex but essential for maintaining patient safety and preventing the spread of infectious diseases. 4. Descriptive Epidemiology Describe Cases: Collect data on person, place, and time. This includes demographics, symptoms, onset dates, and locations within the hospital. Create Epidemic Curves: Plot the number of cases over time to identify the outbreak's pattern. 5. Hypothesis Generation Identify Potential Sources: Use the descriptive data to hypothesize potential sources and modes of transmission. Perform Initial Investigations: Conduct preliminary environmental assessments and interviews to gather more information. 6. Analytical Epidemiology Conduct Case-Control or Cohort Studies: Compare affected individuals (cases) with unaffected individuals (controls) to identify risk factors. Analyze Data: Use statistical methods to test the hypotheses and identify significant associations. 7. Laboratory and Environmental Investigations Collect Specimens: Obtain samples from patients, staff, and the environment for testing. Laboratory Testing: Conduct microbiological, serological, or molecular tests to identify the causative agent. Environmental Assessments: Investigate potential environmental sources, such as water systems, ventilation, or medical equipment. 8. Implement Control Measures Immediate Interventions: Implement control measures such as isolation of patients, staff cohorts, enhanced cleaning, and antimicrobial stewardship. Long-term Interventions: Develop strategies to prevent future outbreaks, such as improving infection control practices and policies. 9. Communication Internal Communication: Keep hospital staff informed about the outbreak status and control measures. External Communication: Inform public health authorities, patients, and the public as appropriate. 10. Evaluation and Follow-up Evaluate the Response: Assess the effectiveness of control measures and the investigation process. Follow-up Surveillance: Continue monitoring to control the outbreak and prevent reoccurrence. 11. Documentation and Reporting Document Findings: Write a detailed report of the outbreak investigation, including methods, findings, and recommendations. Share Results: Share the report with relevant stakeholders and consider publishing findings to contribute to the broader knowledge base. Key Challenges Timeliness: Rapid identification and response are crucial. Coordination: Effective coordination among various departments and external agencies. Resource Availability: Ensuring adequate resources and personnel are available for investigation and control efforts. Steps for investigating cases of hospital- acquired infections or a suspected outbreak Steps for investigating cases of hospital- acquired infections or a suspected outbreak Case Study Example: Hospital-Acquired Infection Outbreak A hospital experienced an outbreak of Methicillin-resistant Staphylococcus aureus (MRSA). The investigation involved: 1.Detection: An increased number of MRSA cases in the ICU was noted. 2.Confirmation: Laboratory tests confirmed MRSA in patients and healthcare workers. 3.Case Definition: symptoms + MRSA-positive culture in ICU patients between specific dates. 4.Data Collection: Reviewed medical records, conducted interviews, and performed environmental sampling. 5.Analysis: Identified a common source, likely a contaminated medical device. 6.Control Measures: Implemented strict hand hygiene, device sterilization protocols, and isolation of infected patients. 7.Communication: Informed staff, patients, and the public about the outbreak and measures taken. 8.Evaluation: Monitored MRSA rates post-intervention to ensure effectiveness. 9.Prevention: Updated infection control policies and conducted staff training. By following these structured steps, outbreak investigations can effectively control and prevent the spread of infections. Healthcare-Associated Infection Surveillance It is limited to monitoring hospital acquired infections by collecting infection data, their locations and agents within hospitals. Upon reporting, feedback should be obtained through data analysis and by taking appropriate interventions. Health care associated infection Surveillance is one of the most vital functions to prevent and control infection. Surveillance This is a continuous process that includes data collection, analysis and interpretation. Also, it requires dissemination of some health issues, in order to take necessary decisions that limit mortalities and the number of infected people.  Monitoring hospital-acquired infection could be utilized in many aspects, as follows: Early detection of abnormal hospital infection increase. Monitor epidemiological patterns and changes in diseases that spread in hospitals. Make appropriate interventions based on the monitoring data. Evaluate infection prevention and control programs adopted at the hospital. Identify health requirements and needs. Establish a database for research and studies. Thank you