MLS 404 — Medical Laboratory Microbiology I: Lecture Note

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LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: MLS 404 Course title: Medical Laboratory Microbiology I Course credit load: 2 Units Series 1: Epidemiology Of Communicable Diseases And Disease Control • Part 1.1: Principles of epidemiology • Sub-Part 1.1.1: Definition and scope of epidemiology • Sub-Part 1.1.2: Key concepts in communicable disease epidemiology • Sub-Part 1.1.3: Modes of transmission of communicable diseases • Part 1.2: Disease spectrum • Sub-Part 1.2.1: Stages of infection and disease progression • Sub-Part 1.2.2: Patterns of disease occurrence (endemic, epidemic, pandemic) • Sub-Part 1.2.3: Host factors influencing disease spectrum • Part 1.3: Disease control strategies • Sub-Part 1.3.1: Principles of prevention and control • Sub-Part 1.3.2: Public health interventions (surveillance, isolation, immunisation) • Sub-Part 1.3.3: Role of laboratory support in disease control • Part 1.4: Applied case studies in communicable disease control • Sub-Part 1.4.1: Case study of malaria control • Sub-Part 1.4.2: Case study of tuberculosis control • Sub-Part 1.4.3: Case study of HIV/AIDS control Introduction Communicable diseases remain one of the most significant challenges to public health worldwide. Their ability to spread rapidly within communities makes them a central focus of medical laboratory microbiology. Understanding how these diseases arise, how they progress, and how they can be controlled is essential for laboratory scientists who play a vital role in diagnosis, surveillance, and prevention. This Series will provide you with the foundational knowledge needed to appreciate the importance of epidemiology in managing communicable diseases.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The aim of this Series is to equip you with the ability to define the principles of epidemiology, explain the spectrum of communicable diseases, and evaluate strategies for their control. By the end of the Series, you will be able to connect theoretical concepts with practical applications in public health and laboratory practice. We shall commence this Series by examining the principles of epidemiology, including its definition, scope, and the modes of transmission of communicable diseases. Next, we will move on to the disease spectrum, where we will explore stages of infection, patterns of occurrence such as endemic and epidemic, and host factors influencing disease progression. Following that, we will study disease control strategies, focusing on prevention, public health interventions, and laboratory support. Finally, we will wrap up with applied case studies, looking at malaria, tuberculosis, and HIV/AIDS control to bring theory into real-world context. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define the principles and scope of epidemiology in relation to communicable diseases, • SLO 1.2 explain the key concepts and modes of transmission of communicable diseases, • SLO 1.3 describe the stages of infection and disease progression within the disease spectrum, • SLO 1.4 analyse patterns of disease occurrence such as endemic, epidemic, and pandemic, • SLO 1.5 evaluate host factors that influence the spectrum of communicable diseases, • SLO 1.6 apply principles of prevention and control to communicable diseases, • SLO 1.7 explain public health interventions including surveillance, isolation, and immunisation, • SLO 1.8 demonstrate the role of laboratory support in disease control, and • SLO 1.9 assess applied case studies of malaria, tuberculosis, and HIV/AIDS control in relation to epidemiological principles. 1.1 Principles Of Epidemiology 1.1.1 Definition and scope of epidemiology Epidemiology is the study of how diseases occur, spread, and can be controlled within populations. It provides the scientific foundation for public health interventions and helps to identify risk factors, patterns of transmission, and strategies for prevention. The scope of epidemiology extends beyond infectious diseases to include chronic conditions, but in this Series our focus will be on communicable diseases. Fill in the blank: The study of how diseases occur, spread, and can be controlled within populations is called __________.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Scope of epidemiology in communicable diseases 1.1.2 Key concepts in communicable disease epidemiology Several key concepts underpin the study of communicable diseases. Incidence refers to the number of new cases of a disease in a population over a specific period. Prevalence refers to the total number of cases, both new and existing, at a given time. Morbidity describes the state of being diseased, while mortality refers to death caused by disease. These measures help epidemiologists assess the burden of disease and evaluate the effectiveness of control strategies. Fill in the blank: The total number of cases of a disease, both new and existing, at a given time is called __________. Concept Definition Example Incidence Number of new cases of a disease occurring in a population during a specified period Annual incidence of influenza cases in a city Prevalence Number of existing cases (new + old) of a disease in a population at a given time Point prevalence of HIV infection in a community Morbidity Measure of illness, disability, or departure from well-being in a population Morbidity due to malaria (episodes of fever and anaemia) Mortality Measure of death due to a disease in a population Mortality rate from tuberculosis in a country Table 1.1: Key concepts in communicable disease epidemiology

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1.3 Modes of transmission of communicable diseases Communicable diseases spread through various modes of transmission. These include direct transmission, such as person-to-person contact, and indirect transmission, which involves vectors, contaminated food or water, or airborne particles. Understanding transmission pathways is crucial for designing effective control measures. For example, malaria is transmitted through mosquito bites, while tuberculosis spreads via airborne droplets. Fill in the blank: Tuberculosis is primarily transmitted through __________ droplets. Plate 1.1: Modes of transmission of communicable diseases Pilot questions 1.1 1. What is the study of how diseases occur, spread, and can be controlled within populations called? 2. What term refers to the number of new cases of a disease in a population over a specific period? 3. What is the total number of cases of a disease, both new and existing, at a given time called? 4. Which term describes death caused by disease? 5. Tuberculosis is primarily transmitted through what type of droplets?

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.2 Disease Spectrum 1.2.1 Stages of infection and disease progression The disease spectrum refers to the range of manifestations that a communicable disease can present in different individuals. The stages of infection typically include incubation period (the time between exposure and the appearance of symptoms), prodromal stage (early, non-specific symptoms), clinical stage (characteristic signs and symptoms), and convalescence (recovery phase). Recognising these stages helps in diagnosis, treatment, and control. Fill in the blank: The time between exposure to a pathogen and the appearance of symptoms is called the __________ period. Figure 1.2: Stages of infection and disease progression 1.2.2 Patterns of disease occurrence Communicable diseases can occur in different patterns. An endemic disease is consistently present in a population, such as malaria in certain regions. An epidemic refers to a sudden increase in cases above the expected level, while a pandemic is an epidemic that spreads across countries or continents. These patterns are important for public health planning and response. Fill in the blank: A disease that is consistently present in a population is described as __________. Pattern Definition Example Endemic Constant presence of a disease within a geographic area or population Malaria in parts of sub-Saharan Africa Epidemic Sudden increase in the number of cases of a disease above expected levels Cholera outbreak in a community

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Pattern Definition Example Pandemic Epidemic that spreads across countries or continents, affecting large populations COVID-19 pandemic (2019 onwards) Table 1.2: Patterns of disease occurrence 1.2.3 Host factors influencing disease spectrum The way a disease manifests can be influenced by host factors. These include age, genetic makeup, nutritional status, immunity, and co-existing conditions. For example, measles may be mild in healthy children but severe in malnourished individuals. HIV infection alters the spectrum of many diseases by weakening the immune system. Understanding host factors helps in predicting disease outcomes and tailoring interventions. Fill in the blank: Malnutrition is a host factor that can make measles more __________. Plate 1.2: Host factors influencing disease spectrum Pilot questions 1.2 1. What is the time between exposure to a pathogen and the appearance of symptoms called? 2. Which stage of infection is characterised by early, non-specific symptoms? 3. A disease consistently present in a population is described as what? 4. What term is used for an epidemic that spreads across countries or continents? 5. Name one host factor that influences the severity of communicable diseases.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.3 Disease Control Strategies 1.3.1 Principles of prevention and control Disease control refers to measures taken to reduce the occurrence and impact of communicable diseases. The principles of prevention and control

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