After reading your module notes, go to the CDC's Solve the Outbreak (accessible version available on the site). https://www.cdc.gov/mobile/applications/sto/web-app.html Navigate to Level 1. There you will be instructed to \"Select a Mission to Solve an Outbreak.\" For this activity, you will select the missions named in the document linked below (\"Case of the Conference Blues\" followed by \"Deadlier than War\"). Depending on your computer screen, you may need to scroll or click and drag to the right to see these cases. Answer the questions in the \"Solve An Outbreak Activity Questions\" sheet either as you progress through each activity, or at the end. You can return to the cases and replay them at any time. Infectious Disease, and Social and Behavioral Epidemiology Specific applications of epidemiology require additional specialization depending upon the focus. While there are numerous applications of epidemiology, this module will focus specifically on infectious disease, and social and behavioral epidemiology. During this module you will learn terms, methodologies, and key concepts necessary for these specific applications of epidemiology. Infectious Disease Epidemiology HIV, chlamydia, hepatitis A, E. Coli, influenza, Lyme disease, measles, malaria, rabies, smallpox and Zika are all examples of infectious diseases. Though chronic diseases are the leading causes of deaths worldwide, significant morbidity and mortality result from infectious diseases. When applying epidemiology to infectious diseases, it is important to understand infectious diseases themselves, and how best to study or control them epidemiologically. Epidemiologic triangle In order for someone to become infected with an infectious disease, there requires the presence of the disease (the agent), someone susceptible to becoming infected with the disease (the host), and the conditions necessary for that disease to survive (the environment). Below is an image of the epidemiologic triangle showing the connection between the host, agent, and environment all of which are required in order for illness to occur. More details will be provided on the role each factor has on the development of the disease. Plain text file Means of transmission of infectious diseases So you now know what factors are necessary for an infection to occur, but how is the agent transmitted from one person to another? First the agent must leave the infected person (reservoir) via a portal of exit which is where the agent leaves the person. A portal of exit can be from a skin lesion, one's genitourinary track, one's alimentary canal, or their respiratory passages. Once the agent is outside of the host, transmission can occur either through direct or indirect processes. The image below shows the chain of infection by which an agent is transmitted through some mechanism (defined in the next section of the module) by leaving a reservoir via a portal of exit, by means of direct or indirect transmission, to a susceptible host through a portal of entry (NOTE: see how important it is to be able to define key terms used in the study of infectious diseases!). Source: Centers for Disease Control and Prevention. Principles of epidemiology, 2nd ed. Atlanta: U.S. Department of Health and Human Services;1992. Public domain. Direct transmission Direct transmission is when an infectious agent is transmitted directly from one person to another (person-to-person). Think of kissing someone who has mononucleosis (mono). Or having sexual relations with someone infected with a sexually transmitted infection. If these encounters resulted in you becoming infected with the same disease, these would be examples of direct transmission. Just as an infected host requires of portal of exit, a susceptible host requires a portal of entry (which are the same as portals of exit). Indirect transmission Indirect transmission occurs when an infectious agent passes through a middle ground before infecting a susceptible host. Vehicle-born infections: These are infections that result following contact with a vehicle that is contaminated. Think of a vehicle as a non-living object that can carry the agent. This could be a food item or water product contaminated with some infectious disease. This could also be an inanimate object (a fomite) such as a door knob, or a syringe used to inject drugs. Airborne infections: These are infections that travel in particles in the air. This could result from stirred up dust that contains an agent, or from an agent aerosolizing in some manner. Your text provides an example of someone traveling via aircraft who had severe acute respiratory syndrome (SARS). In this example, the index patient is sitting in row 14 (midway on the aircraft). Because SARS is airborne, persons sitting throughout the aircraft became infected. Vector-borne infections: Unlike vehicle-born infections that involve a non-living object, vectorborne infections involve a living object. This could be an insect or an animal. Can you think of any infectious diseases that result from the bite of a mosquito? Or a tick? Classifications of infectious diseases Further classification of infectious diseases into specific categories of diseases is also important in their epidemiologic study. In this module, we will discuss: sexually transmitted diseases, foodborne illnesses, vector-borne diseases, and vaccine-preventable diseases. Again, knowing how they are transmitted, and what factors need to be present for transmission to happen is important in being able to discuss and understand their occurrence, but being able to further classify infectious diseases into categorizes of diseases aids in understanding the best way to study them epidemiologically. Sexually Transmitted Diseases Sexually transmitted diseases (STDs), are diseases or infections that can be transmitted through sexual contact. These include Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS), herpes, syphilis, chlamydia, gonorrhea, and hepatitis B, to name a few. STDs can have temporary or permanent impacts on the health of the infected individual including increasing susceptibility to other STDs and infections, damage to major organs resulting from long term infections, and potential transmission from mother to child during childbirth or through breast feeding. You can find more information on STDs on the CDC website. Syphilis, which you learned about in the last module and can lead to visual impairment and stroke, is showing an alarming rise among young men who have sex with men (MSM). The image below shows the increase over time of syphilis among young MSM in the United States: In the graph above, the year is on the x-axis (from 2007-2014), and the number of infections is on the y-axis (from 2,000-14,000). The lines representing men who have sex with women (MSW), and women show a relatively steady number of new infections per year, remaining at roughly 2,000 infections/per year. MSM show an alarming rise from under 6,000 in 2007 to almost 14,000 infections in 2014. Foodborne illness Foodborne illnesses are those agents that are transmitted via food. These can include E.Coli, Vibrio, Botulism, Listeria, and Salmonella. The most common initial symptoms of foodborne illnesses are nausea, vomiting diarrhea and/or abdominal cramps. Although foodborne illnesses can be self-limiting (go away on their own), some other illnesses left untreated can lead to permanent damage. To name a few, botulism can lead to permanent paralysis, and typhoid fever and vibrio can lead to death. It is also important to note that diarrhea and vomiting can lead to dehydration which can be a serious threat for young, old, or individuals who are immunocompromised. You can find more information on foodborne illnesses on the CDC website. Vector-borne diseases You already glimpsed vector-borne diseases when you learned about vectors in the context of transmission. Some examples of vector-borne diseases include West Nile virus, Lyme disease, Malaria, the Plague, Zika virus, and Eastern Equine Encephalitis. Common vectors include ticks and mosquitos. You can find more information about vector-borne diseases on the CDC website. Vaccine-preventable diseases Vaccine-preventable diseases (VPDs) are those diseases or infections that are preventable through vaccines. In the United States, there are mandatory vaccines for children that have significantly reduced the morbidity and mortality associated with the diseases they prevent. You can find more information about VPD's on the CDC website. Outbreak investigations Infectious disease outbreaks require specialized methodologies to study given the urgency in discovering a cause, and therefore a way to stop additional transmission. The steps of an outbreak investigation are provided below with some new terms that will be defined as you progress through the module: Infectious disease outbreaks require specialized methodologies to study given the urgency in discovering a cause, and therefore a way to stop additional transmission. The steps of an outbreak investigation are provided below with some new terms that will be defined as you progress through the module: Defining the problem- is there an actual outbreak? Are cases of the same disease or infection related to one another? Appraising existing data- Do you know of all of the cases? Did you collect specimens from all cases, and record their symptoms? Can you calculate an incubation period? After plotting the cases on an epidemic curve, what do you see? Can you calculate the attack rate? Can you map the cases? Formulate a hypothesis- What is the likely cause of the outbreak given all of the data? Confirm the hypothesis- Can you test the suspected source in a lab? Draw conclusions and implement a plan- Is there a way to stop additional cases from happening? The incubation period is the time from exposure to symptoms (or the time from when one is infected with the agent, to when they start to show symptoms). Understanding the incubation period will provide clues into the agent causing the outbreak, as different agents have different incubation periods. Plotting the epidemic curve is a graphical methodology employed that you have already glimpsed in previous chapters. The epidemic curve requires plotting cases over time. This method allows you to see how quickly cases appeared, how numerous the cases are, and if the cases are tapering off. To practice the application of creating an epidemic curve, you can participate in this optional exercise created by the CDC - Create An Epi Curve. Lastly, the attack rate is an important epidemiologic measure used for outbreak investigations that can provide insight into the cause of the outbreak. The attack rate is a type of incidence rate that is calculated as follows: Attack rate= # ill/(# ill + # well) x 100 A high attack rate would be indicative of a likely source (NOTE: there is no clear cut definition of a \"high attack rate;\" interpretation of attack rates is a subjective practice that requires additional information before drawing conclusions). But be careful when interpreting attack rates, especially for foodborne outbreaks. Multiple food sources can have high attack rates if the source of the outbreak was used in both dishes. Let's try an example of calculating an attack rate! There were 100 people who ate at a local restaurant over the weekend, and 50 ate the macaroni salad. Of those who ate the macaroni salad, 39 got sick. The attack rate would be calculated as follows: Attack rate for macaroni salad= 39/(39+11) x 100 = (39/50) x 100 =78% Social and Behavioral Epidemiology Unlike infectious diseases in which you learned specific terms, and methodologies utilized to study infectious disease epidemiology, this next section will provide an overview of what social and behavioral epidemiology is, and highlight key concepts that are studied. Whereas with infectious disease epidemiology, there is a specific focus on a microbial agent that is the cause of morbidity and mortality, social and behavioral epidemiology focuses on social adversities, lifestyle, and stress as the cause of morbidity and mortality. Perhaps slightly more abstract, social and behavioral factors can impact one's health in such a way that illness or death may occur. Very simply put, social epidemiology studies the relationship between social factors and health, whereas behavioral epidemiology studies the relationship between behavioral factors and health. For the remainder of the module, different social and behavioral factors will be introduced and discussed in the context of the impact on one's health. Although statistics are presented in your text highlighting the epidemiology of the below mentioned factors, a reiteration of statistics will not be provided in the module notes; the module notes will focus on introducing important factors to consider when studying social and behavioral epidemiology. Stress and Health Stress, which is a physical, chemical, or emotional factor that leads to tension in the body or mind. Stress has been shown to be linked to a variety of adverse health outcomes. As stated in your text, stress has been linked to: Cardiovascular disease Substance abuse Mental disorders Anxiety Chronic diseases Impaired immune function Research shows that the more serious a stressor, and the more sustained that stressor is, the more likely it is to result in adverse health outcomes. It is important to note that there are mitigating factors to the impact of stress on health. These include social support, and coping skills. Tobacco Use Use of tobacco, specifically smoking cigarettes has been linked to a plethora of negative health outcomes including cancer of the lung, cervix, kidney, pancreas, cervix, and stomach, as well as coronary heart disease, and stroke. The image below from the CDC shows the variety of health ailments associated with cigarette smoking. The image shows by highlighting specific areas of the body that smoking can lead to a variety of cancers, and chronic diseases (some already mentioned above): Another way that tobacco use is harmful is its potential impact to people exposed to secondhand smoke. This occurs when someone involuntarily inhales cigarette smoke from someone who is smoking nearby. The research on the negative health outcomes among persons exposed to secondhand smoke has been so extensive, that there have been a drastic number of health policies put in place to protect people from secondhand smoke. Disallowing smoking in work places, airplanes, public transportation, and restaurants have been major public health successes. Smoke free parks, and work and college campuses have also been implemented in a variety of states. Alcohol Consumption Alcohol consumption, whether it be binge drinking, heavy drinking, excessive drinking, alcohol use, or alcohol dependence can have short and long term health risks. Short term health risks include injuries, risky sexual behaviors, alcohol poisoning, violence, and miscarriage. Long term health risks include different types of cancer, mental health problems, social problems, liver disease, high blood pressure, and heart disease. Someone who is alcohol dependent might be subject to additional health problems related to loss of social support, or occupation which would lead to unemployment. Substance Use Like alcohol consumption, use of illegal substances can have similar short and longer term health risks. The number and severity of those risks vary by substance, and frequency of use. Overweight and Obesity Roughly 30% of people living in the United States are obese. Being overweight or obese can have long term impacts on one's physical health, but also one's mental and emotional health. Stigma associated with being overweight or obese, especially among children, can be another stressor which has additional implications for one's health. As you can see, the application of epidemiology specific to infectious diseases, and social and behavioral factors requires additional knowledge specific to the application. There are more specialized applications of epidemiology than there exists time in this course to cover. However, in the last and final module of the course, you will be introduced to the following special epidemiologic applications: molecular and genetic, epidemiology, environmental epidemiology, occupational health, and unintentional injuries. Solve an Outbreak! Activity Questions After completing the \"Case of the Conference Blues\" and \"Deadlier than War\" mysteries online, answer the following questions in this document. You will submit it as an assignment for Module 7. Remember to save this document to your computer first, then complete the questions. Point values for each question of this activity are provided. \"Case of the Conference Blues\" 1. What was the infectious disease agent involved in this outbreak? (1 point) 2. What is the means of transmission of the infectious disease agent in this case study (i.e direct or indirect)? If the means of transmission is indirect, specify if the infection is vehicle-born, airborne or vector-borne. (2 points) 3. When did the number of cases peak? (Make sure to use the epi-curve provided in Clue 2) (1 point) 4. Although the attack rate for the spinach dip is higher than that of the veggie lasagna, why can you not conclude that the spinach dip is the source of the outbreak? (1-2 sentences) (3 points) 5. In Clue 2, relative risks for getting sick by each food item was calculated. Create the 2*2 table for calculating the relative risk of illness as a result of eating the spinach dip using the information provided in the clue. (5 points) Extra credit: calculate the relative risk for eating spinach dip. Show your work. (2 extra points) Ill Not ill Total Ate spinach dip Did not eat spinach dip Total \"Deadlier than War\" 1. What was the infectious disease agent involved in this outbreak? (1 point) 2. What is the means of transmission of the infectious disease agent in this case study (i.e direct or indirect)? If the means of transmission is indirect, specify if the infection is vehicle-born, airborne or vector-borne. (2 points) 3. When did the number of cases peak? (Make sure to use the epi-curve provided in Clue 1) (1 point) 4. Calculate the attack rate for the conference attendees who: 1) stayed at, 2) visited, or 3) did not visit the hotel during the days of interest using the made up numbers below. (3 points) Conference attendees Stayed at the hotel Visited the hotel Excelsior College PBH 321 # ill 50 45 # well 5 25 Attack rate Did not visit the hotel Excelsior College PBH 321 5 55