Disease Surveillance PDF

Disease Surveillance BSc Medical Sciences: Epidemiology Assistant Prof. Dr. Soza Th. Baban Introduction and Review In session 5, we discussed: Definition of screening tests Validity components including: Sensitivity test Specificity test Predictive accuracy of test Learning objectives 1. To...

Disease Surveillance BSc Medical Sciences: Epidemiology Assistant Prof. Dr. Soza Th. Baban Introduction and Review In session 5, we discussed: Definition of screening tests Validity components including: Sensitivity test Specificity test Predictive accuracy of test Learning objectives 1. To define and explain the differences between disease monitoring and disease surveillance. 1. To describe the various types of disease surveillance systems. 1. To the key elements of an effective surveillance system, including data collection, analysis, reporting and response. 1. Discuss the challenges, importance and the role of disease surveillance in preventing and controlling outbreaks. Let’s go through each of these points in detail!  Disease Monitoring and Surveillance Disease Monitoring: Disease Surveillance: The ongoing systematic collection, A more specific and active process analysis, and interpretation of health of detecting disease outbreaks, data essential to planning, involving the collection, analysis, implementation, and evaluation of and dissemination of data for early public health practice. warning and response.  Disease monitoring It is the performance and analysis of routine measurements aimed at detecting changes in the environment or health status of a population. Monitoring air pollution, water quality, and nutritional status. Ongoing measurement of health service performance and patient compliance. It keeps track of achievements, staff movements and utilization, supplies and equipment, and expenditure relative to available resources, ensuring immediate corrective measures can be taken if necessary. Disease Monitoring: Examples: Recording vaccination coverage rates across regions to ensure compliance with immunization programs. Total number of COVID-19 vaccine doses administered by country in 2021.  Tracking obesity rates in a population through routine health surveys.  Monitoring air quality and its impact on respiratory diseases (e.g, their effect on asthma cases.  Monitoring hospital infection rates of Methicillin-resistant Staphylococcus aureus (MRSA) over years to assess long-term trends. Recording antibiotic prescription rates in outpatient clinics to evaluate misuse. Methicillin-resistant Staphylococcus aureus  Monitoring for new cases of polio in countries at risk of re-emergence. The spread of Circulating Vaccine-Derived Poliovirus Type 2 in 2022. This figure highlights areas with outbreaks, particularly where immunization coverage is low, and illustrates the ongoing use of Oral Polio Vaccine Type 2 (OPV2) in response to such outbreaks.  Disease Surveillance Surveillance means watch over with great attention, authority, and often with suspicion, and is described as "the continuous detailed investigation of the factors that determine the occurrence and distribution of disease.  Objectives of Disease Surveillance A. To provide information about new and changing trends in the health status of a population, e.g., morbidity, mortality, nutritional status, health practices and other factors that may affect health; B. To provide feed-back for Policy and Health system improvement based on the data collected and analysed; C. To provide timely warning of public health disasters so that interventions can be mobilised.  Disease Surveillance Detecting and responding to outbreaks of foodborne diseases like salmonellosis.  Real-time surveillance of COVID-19 cases to identify outbreaks and hotspots.  Disease Surveillance Surveillance for Marburg virus to prevent its spread to unaffected regions. Detecting new antibiotic resistance genes, such as mcr-1, and coordinating rapid containment responses. Fluoroquinolone-resistant Escherichia coli (2019) (Source: Lancet) Marburg virus disease (MVD) is one of the most virulent pathogens known to humankind, posing a serious public health threat. While sporadic outbreaks have occurred in Africa since the first recognized cases in 1967, the outbreak in Rwanda, first reported by the Ministry of Health on 27 September 2024, is the country’s first, and has rapidly affected urban areas in the capital, Kigali. Active surveillance of multidrug-resistant tuberculosis (MDR-TB) cases in high-risk populations. The eight countries ranked in descending order of their total number of MDR/RR-TB incident cases in 2022 are India, the Philippines, the Russian Federation, Indonesia, China, Pakistan, Myanmar and Nigeria.  Key Elements of an Effective Surveillance System These elements form the foundation upon which a surveillance system operates: 1. Data Collection: Accurate and timely data must be gathered from reliable sources such as hospitals, clinics, laboratories, and communities. Example: During the Ebola outbreak in West Africa, health workers relied on direct patient data from clinics and communities to track the spread of the virus.  Key Elements of an Effective Surveillance System 2. Data Analysis: The collected data must be interpreted to identify trends, patterns, and potential outbreaks. This involves sophisticated statistical techniques to detect early warning signs. Example: Influenza surveillance systems analyse trends in flu cases to predict the onset of flu season and tailor vaccination efforts accordingly.  Key Elements of an Effective Surveillance System 3. Data Reporting: Information must be disseminated quickly to public health authorities, healthcare providers, and sometimes the public to ensure a rapid response. Example: During the COVID-19 pandemic, governments used data reporting systems to inform the public about case numbers and vaccination availability.  Key Elements of an Effective Surveillance System 4. Response: Public health measures such as vaccination, quarantine, or health education campaigns must be implemented based on surveillance data to prevent the further spread of disease. Example: SARS-CoV-2 (COVID-19) led to global lockdowns, travel restrictions, and mass vaccination campaigns based on real-time surveillance data.  Key Challenges in Disease Surveillance Surveillance systems face significant challenges that can hinder outbreak control and prevention, leading to poorer public health outcomes. The most common challenges are discussed below: 1. Underreporting of Data 2. Data Quality 3. Resource Limitations  Key Challenges in Disease Surveillance 1. Underreporting of Data Issue: Limited healthcare access, lack of awareness, or poor infrastructure. Impact on Public Health: Creates data gaps, delaying outbreak detection and response. Real-World Example: In the early COVID-19 pandemic time, underreporting in some Sub- Saharan African countries masked the outbreak's true scale, delaying aid, uncontained transmission and worsening health outcomes.  Key Challenges in Disease Surveillance 2. Data Quality Issue: Inaccurate, incomplete, or outdated data weakens surveillance systems. Impact: Leads to incorrect trend analysis and flawed predictions, hindering responses. Real-World Example: During the 2014 Ebola outbreak, poor reporting in rural West Africa led to underestimated case numbers, delaying the WHO's global response and contributing to rapid virus spread and higher deaths.  Key Challenges in Disease Surveillance 3. Resource Limitations Issue: Low-income countries lack funding, trained personnel, and infrastructure for effective surveillance. Impact: Limited resources prevent proper data collection and response, leading to undetected outbreaks. Real-World Example: During the early HIV/AIDS epidemic in Sub-Saharan Africa, resource shortages delayed detection and response, allowing the disease to spread until international aid helped improve surveillance.  Key Challenges in Disease Surveillance 4. International Cooperation Issue: Low-income countries lack funding, trained personnel, and infrastructure for effective surveillance. Impact: Insufficient resources hinder data collection and analysis, leading to undetected outbreaks. Real-World Example: During the HIV/AIDS epidemic in Sub-Saharan Africa, limited resources delayed detection and response, allowing the disease to spread until international aid improved surveillance systems.  Three Case Studies addressing Surveillance Challenges 1. Case Study: The Global Polio Eradication Initiative (GPEI) 2. Case Study: The Global Influenza Surveillance and Response System (GISRS) 3. Case Study: HIV/AIDS Surveillance in South Africa (Session 6 - Impact of Surveillance Case Studies)  The key elements of an effective Global Influenza Surveillance and Response System (GISRS) GISRS is a global public health network, coordinated by the WHO, that monitors and responds to influenza viruses. This system is vital for preventing seasonal flu and managing pandemics. (Session 6 - Surveillance System Information handout)  Types of Disease Surveillance Systems Sentinel Surveillance targets specific institutions, communities, or groups to monitor key health indicators. These sentinel sites are strategically chosen to detect early disease trends before they spread more widely. Sentinel surveillance is especially useful for diseases that are rare or hard to track.  Sentinel Surveillance Objectives: Early warning of potential outbreaks by focusing on specific groups. Monitoring health indicators in selected populations that are representative of larger trends. Evaluating the effectiveness of public health interventions in real-time. Real-World Example: The UK’s influenza sentinel surveillance system monitors flu-like symptoms in a network of general practitioners (GPs) across the country. Selected GPs report cases of flu-like illnesses during the flu season, which helps public health authorities predict upcoming flu outbreaks and adjust vaccination strategies.  Sentinel Surveillance Strengths and Weaknesses: Provides early warning signs of outbreaks in high-risk populations. Less resource-intensive than active surveillance since it focuses on a small, representative group. Limited in scope; only covers specific populations or regions, so it may miss outbreaks in other areas. Data from sentinel sites may not always be generalisable to the entire population.  Syndromic Surveillance Syndromic surveillance uses real-time data from non-traditional sources (e.g., pharmacy sales, school absenteeism, or online search queries) to detect unusual patterns of illness that might indicate the early stages of a disease outbreak. It focuses on symptoms rather than confirmed diagnoses.  Syndromic Surveillance Objectives: Early detection of potential outbreaks before laboratory confirmation is available. Continuous monitoring of health trends using real-time data. Fast response to emerging public health threats, even without detailed clinical data.  Syndromic Surveillance Real-World Example: COVID-19 and Google Flu Trends During the early stages of the COVID-19 pandemic, syndromic surveillance systems were used to detect increases in flu-like symptoms. Google Flu Trends, an experimental service by Google, predicted flu outbreaks based on people’s search queries for flu-related symptoms. Though imperfect, the system highlighted how syndromic surveillance could provide early insights into disease spread before clinical confirmation.  Syndromic Surveillance Strengths and Weaknesses: Provides rapid detection, especially useful in the early stages of an outbreak. Utilises non-traditional data sources, which can complement traditional surveillance systems. May produce false alarms due to overreliance on symptom reporting rather than confirmed cases. Requires sophisticated data analysis and algorithms, which may not always be accurate or available.  Exploring Different Types of Disease Surveillance Systems Group Discussion Questions: 1. Which type of surveillance system do you think is most effective in detecting new, emerging diseases? Why? 2. What challenges do you foresee in implementing active surveillance in low-resource countries? 3. How could syndromic surveillance be improved to reduce the risk of false alarms? (Session 6 - Surveillance Systems Case Study)  How Does Disease Surveillance Prevent and Control Outbreaks? Early Detection: Timely surveillance which involves collecting and analyzing data promptly to spot potential health threats as they arise. Examples: COVID-19, Ebola virus, hospital- acquired MRSA and CA-MRSA  How Does Disease Surveillance Prevent and Control Outbreaks? Public Health Response: Surveillance informs interventions such as: Vaccination campaigns target at-risk populations based on data. Quarantine measures are deployed to contain outbreaks. Public awareness initiatives educate communities on prevention. Example: Surveillance during the Ebola outbreak enabled targeted vaccination and treatment centres.  The Spectrum of Disease Control The term "disease control" describes (ongoing) operations aimed at reducing: 1. the incidence of disease; 2. the duration of disease, and consequently the risk of transmission; 3. the effects of infection, including both the physical and psychosocial complications; 4. the financial burden to the community. Review this report from CDC: Recommendations of the International Task Force for Disease Eradication  The Spectrum of Disease Control Between the extremes of disease "control" (reduction in incidence and/or prevalence) and "eradication," several intermediate levels of impact on diseases are described. Disease elimination Is the reduction to ZERO of the incidence of a specified disease (neonatal tetanus) or infection caused by a specific agent (polio virus) in a defined geographical area as a result of deliberate efforts; continued measures to prevent re-establishment of transmission of the specific agent are required. It is a control of the manifestations of a disease so that the disease is no longer considered "a public health problem,"  Disease eradication Means to ‘’tear by roots’’. It is a permanent reduction to ZERO of the worldwide incidence of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer need. Implies termination of all transmission of infection by extermination of the infectious agent. True eradication usually entails eliminating the microorganism itself or removing it completely from nature, as in the case of smallpox virus, which now exists only in storage in two laboratories.  Disease eradication Once the morbidity of a disease reaches a very low level, a ‘’residual’’ infection usually persists in the population leading to a state of equilibrium between the agent, host and environmental components of the disease process. In this situation there are always hidden foci of infection, unrecognised methods of transmission, resistance of the vector or organism, all of which may again flare up when the agent- host-environment equilibrium is disturbed. Surveillance-Led Public Health Interventions and Their Role in Disease Prevention and Control 1. The Eradication of Smallpox 2. Global Influenza Surveillance and Response System (GISRS) Reference: https://www.who.int/initiatives/global-influenza-surveillance-and-response-system 3. The Control of Ebola Outbreaks (Session 6 – Surveillance-Led Interventions Case Study) The Intensified Eradication Program began in 1967 by WHO. smallpox was eradicated in 1980, becoming the first human disease to be eradicated through vaccination and public health measures. History of Smallpox | Smallpox | CDC  Eradication of Smallpox Key Elements: Early Detection: Surveillance efforts were critical in tracking outbreaks of smallpox, particularly in developing countries where the disease was most prevalent. WHO established surveillance units that monitored outbreaks and worked to vaccinate affected populations rapidly.  Eradication of Smallpox Public Health Response: The cornerstone of the eradication program was the ring vaccination strategy, which focused on identifying and vaccinating individuals in close contact with infected persons. This targeted approach was based on surveillance data and allowed health authorities to contain outbreaks before they could spread.  Eradication of Smallpox International Cooperation: The success of the eradication program relied heavily on the cooperation of national governments, health workers, and WHO. Vaccines, technical assistance, and funding were provided globally to support the eradication effort.  Eradication of Smallpox Impact on Public Health: The eradication of smallpox is considered one of the greatest achievements in public health history. Before eradication, smallpox killed 3 out of every 10 people infected and left many survivors disfigured or blind. Eradicating smallpox saved an estimated 5 million lives annually, and it serves as a model for how surveillance-led interventions can achieve global health goals. Global Influenza Surveillance and Response System (GISRS) The Global Influenza Surveillance and Response System (GISRS) is one of the most prominent examples of a surveillance-led intervention. It was established by the World Health Organisation (WHO) and has been operational for more than 70 years. GISRS plays a critical role in monitoring the spread of influenza viruses, identifying new strains, and coordinating global responses to seasonal and pandemic influenza outbreaks. Global Influenza Surveillance and Response System (GISRS) Key Elements: Early Detection: GISRS operates through a network of 153 national influenza centres across 114 countries. These centres collect and analyse respiratory samples to detect influenza viruses and their mutations. This early detection allows countries to prepare for flu seasons and respond quickly to novel strains. Global Influenza Surveillance and Response System (GISRS) Public Health Response: The system informs the development of the seasonal influenza vaccine. Twice a year, WHO issues recommendations for the composition of the flu vaccine based on GISRS data, ensuring the vaccine targets the most prevalent strains. Global Influenza Surveillance and Response System (GISRS) International Cooperation: GISRS relies on collaboration between national health authorities, WHO, and laboratories worldwide. This cooperation is essential for sharing real-time data and ensuring that all regions are prepared for influenza outbreaks. Global Influenza Surveillance and Response System (GISRS) Impact on Public Health: GISRS has been instrumental in reducing the global burden of influenza, which causes up to 650,000 deaths annually. By ensuring timely identification of strains and coordinating international vaccine responses, GISRS has saved countless lives and prevented the widespread transmission of influenza, particularly during the H1N1 pandemic in 2009.  The Control of Ebola Outbreaks The 2014-2016 Ebola outbreak in West Africa was one of the deadliest in recent history, resulting in more than 28,000 cases and 11,000 deaths. Surveillance systems were crucial in controlling the outbreak and preventing its spread to other regions of the world. The lessons learned from this crisis have shaped future responses to outbreaks of similar scale and severity.  The Control of Ebola Outbreaks Key Elements: Early Detection: Surveillance in the early stages of the outbreak was weak due to poor health infrastructure in countries like Liberia, Sierra Leone, and Guinea. Once the severity of the outbreak was recognised, international partners, including WHO and Centres for Disease Control and Prevention (CDC), helped strengthen local surveillance systems by training healthcare workers and providing mobile laboratories for rapid testing.  The Control of Ebola Outbreaks Public Health Response: Once reliable surveillance systems were established, they guided the response by identifying transmission hotspots. Public health authorities implemented quarantine measures, set up treatment centres, and launched contact tracing efforts to monitor and isolate individuals who had come into contact with Ebola patients.  The Control of Ebola Outbreaks International Cooperation: The global response to the Ebola outbreak involved cooperation between national governments, international organisations, non-governmental organisations (NGOs), and local communities. This collaboration led to the development of a new Ebola vaccine, which was successfully deployed during the latter stages of the outbreak.  The Control of Ebola Outbreaks Impact on Public Health: Despite the high death toll, the Ebola outbreak was eventually contained thanks to a combination of enhanced surveillance, public health interventions, and international cooperation. The outbreak highlighted the importance of strengthening surveillance systems in low-resource settings and prompted the development of new vaccines and treatments for Ebola.  Recap and Q&A Today, we covered screening of disease measures with examples: Disease surveillance is essential for detecting, responding to, and preventing outbreaks. Effective disease surveillance systems require accurate data, timely reporting, and international cooperation. Different types of surveillance systems serve different needs, from local to global. Preparation for Next Session In the next session we'll explore the natural history of disease and its impact on public health interventions. Read Chapter 3 (Pages 41-64) from "Gordis Epidemiology" by Celentano DD and Szklo M. Read Chapter 6 (Pages 123-146) from "Gordis Epidemiology" by Celentano DD and Szklo M. Review Chapter 3 (Pages 41-51) from "Parks Textbook of Preventive & Social Medicine" by K. Park.