You might also use spot maps to represent affected villages, towns, or other smaller population units. Ideally, code response categories in advance and on the instrument to facilitate data entry and analysis (e.g., yes = 1, no = 0). To support person-to-person transmission, you should also see that the timing between onsets of cases approximates the known incubation periods for the disease (Figure 6.8) (5). Public Health Problem: To support a rapid response, field epidemiologists need to determine the most efficient, timely, and cost-effective method for data collection during an outbreak. Many emerging infectious diseases are zoonotic in origin, so related data are needed. Am J Epidemiol. Reduce embellishments that obstruct a clear vision of disease and potential exposures. Deputy Director for Public Health Science and Surveillance, Center for Surveillance, Epidemiology, and Laboratory Services, Division of Scientific Education and Professional Development, U.S. Department of Health & Human Services. The last three questions are assessed as patterns of these data in terms of time, place, and person. These include forms for recording screening, baseline, treatment, and outcome measures, as well as tools to monitor data accrual, visit scheduling, events such as adverse reactions to study treatment or out-of-protocol events. By September, an increased number of infants with microcephaly was reported from Zika virus–affected areas. Although some existing data sources (e.g., death certificates) cover many disease outcomes, others are more specific (e.g., reportable disease registries). Control over completeness and order of questions. The analyses and results are only as good as the quality of the data collected (remember GIGO!). Plotting only numerators loses the advantage of both the spot map (indicating exact location and detailed background features) and the area map (indicating rates). In September 2009, the Oregon Public Health Division investigated an outbreak of gastroenteritis that occurred among more than 2,000 participants of a week-long, 475-mile bicycle ride. Cases of salmonellosis among passengers on a flight from London to the United States, by time of onset, March 13– 14, 1984. Is the objective to identify specific behaviors that put people at increased risk (e.g., cross-contamination during food handling)? Data collection is the process of gathering and measuring information on variables of interest, in an established systematic fashion that enables one to answer stated research questions, test hypotheses, and evaluate outcomes. Equal rates of change in time (e.g., a 10% decrease/year) will yield misleading, divergent lines on an arithmetic plot; a logarithmic scale will yield parallel lines. Temporal disease rates are usually illustrated by using a line graph (Box 6.4). Having a written data collection section as part of the overall study protocol is essential. They can have various response categories (e.g., nominal, numeric, Likert scales). Six biologic differences in human–vector–human propagation affect the size and the shape of the epidemic curve (Box 6.7). Age-specific mortality rates per 100,000 population/year: United States, 1910, 1950, and 1998. Epidemiologic data are paramount to targeting and implementing evidence-based control measures to protect the public’s health and safety. Cholera deaths per 10,000 inhabitants and altitude above the average high-tide level, by district in London, England, 1849. Indicate underpopulated or depopulated areas. After evaluating whether existing data can address the study objectives, the field epidemiologist must determine whether additional data need to be collected and, if so, what and how (Box 4.4). Differentiate them with labels, legends, or keys. Never mix incident with prevalent cases in epidemiologic analyses. These can then be counted and the rates calculated. Rates correct counts for differences among population sizes or study periods. To indicate numeric intensity, use increasing intensity of gray from white to black. Include a legend or key to clarify map features (e.g., disease cases, rates, and exposures). Consider instead. A sample can be selected through probability sampling or nonprobability sampling (e.g., purposive sampling or a convenience sample). Ensure that potential exposures are easily discerned and labeled. An epidemic curve with a tight clustering of cases in time (≤1.5 times the range of the incubation period, if the agent is known) and with a sharp upslope and a trailing downslope is consistent with a point source (Figure 6.3) (6). With acute infections, poisonings, and injuries, you will often have precise exposure times to different suspected agents. Two important qualifications apply to person data assessments. Similar to developing a protocol, the most efficient and effective means for developing a survey instrument might be to identify an existing survey questionnaire or template that can be adapted for current use. Participatory epidemiology can be utilised primarily as a data collection method in which case it is more closely related to RRA. The following sections describe certain kinds of epidemic situations that can be diagnosed by plotting cases on epidemic curves. Source: Adapted from Ajloun Non-Communicable Disease Project, Jordan, unpublished data, 2017. The underlying epidemiologic process might produce disease distributions within and among social groupings that range from strong aggregation to randomness or uniformity. 6th Edition. Information was drawn in part from the “Surveys and Sampling” chapter in the earlier edition of this book (27) and from Designing Clinical Research (28). Data collection procedures, variables to be collected, procedures to safeguard participants. Seasonal distribution of malaria cases, by month of detection by voluntary collaborators in four villages: El Salvador, 1970–1977. Instructions on conducting the interviews, especially if there are multiple interviewers: Include the importance of reading the questions verbatim, term definitions, the pace of the interview, answers to frequently asked questions, and ways to handle urgent situations. Variations in slopes (e.g., bimodal or a broader than expected peak) might indicate different ideas about the appearance, persistence, and disappearance of exposure to the source. Since this outbreak was recognized, the epidemic has spread through the mosquito vector as well as through sexual and perinatal transmission to multiple countries and continents around the world. In contact diagrams (Figure 6.2, panel A) (5), which are commonly used for visualizing person-to-person transmission, different markers are used to indicate the different groups exposed or at risk. Use alternating light shading of rows to assist readers in following data across a table. During 2014–2015, a sharp increase in the percentage of children with elevated blood lead levels in Flint, Michigan, resulted from exposure to drinking water after the city introduced a more corrosive water source containing higher levels of lead (Box 4.3) (14). All articles in the collection are completely free to access, download, and share until the end of 2020. Doing so facilitates data exchange with other systems if the outbreak extends to other jurisdictions. Arthropod vectors, after becoming infected, remain so until they perish. Epidemic curves from environmentally spread diseases reflect complex interactions between the agent and the environment and the factors that lead to exposure of humans to the environmental source. < Previous Chapter 3: Conducting a Field Investigation, Next Chapter 5: Using Technologies for Data Collection and Management >. Close-ended questions could include cascading questions, which can be an efficient way to get more detailed information as one filters down through a hierarchy of questions (e.g., first you ask the participant’s state of residence, then a menu of that state’s counties drops down). Epidemiology is a scientific discipline with sound methods of scientific inquiry at its foundation. Generally, government public health agencies have the authority to access healthcare system data (with justification). Data for healthcare epidemiology come from three sources: direct ascertainment of information from subjects using questionnaires or direct observation; review of medical records; and electronic sources, such as billing records, laboratory records, and medication administration records. Dot chart (A) and bar chart (B) comparison of mean body mass index among adults, by age group and sex: Ajloun and Jerash Governorates, Jordan, 2012. On maps representing land areas, indicate longitude and latitude and orientation (i.e., by using a northward-pointing arrow). For example, a plot of the days between contact with a SARS patient and onset of SARS in the person having contact indicates an approximation of the incubation period (Figure 6.8) (5). To indicate divergence from an average range, use white for the center range and deepening intensities of two different hues for divergent strata on opposite extremes. This type of curve can be made for any time cycle (e.g., time of day, day of week, or week of influenza season). These three points should bracket the exposure period. The last two factors listed in the box will lead to irregular peaks during the progression of the outbreak and precipitous decreases. Other scenarios that challenge epidemiologists trying to access external data include concern by healthcare systems that requests for data on hospitalizations, clinic visits, or emergency department visits breach privacy of protected health information; concern by school officials that access to information about children during an outbreak associated with a school activity violates provisions of the Family Educational Rights and Privacy Act (32); and concerns by businesses that case-patients in an outbreak associated with a particular food item or establishment might pursue legal action or lawsuits. If large amounts of data need to be collected manually, not having adequate data entry … Study population, case definition, sample size, and selection. Compare the association of cases during these pre-and post-epidemic periods with the main outbreak. Returning now to counts, you can calculate expected case counts for a population by multiplying an expected (e.g., historical counts, increased surveillance, or output from prevention and control programs) or a target rate by the population total. To assess the impact of drinking contaminated water on blood lead levels (BLLs), the distribution of BLLs 5 μg/dL or higher among children less than 6 years of age before, during, and after the switch in water source was assessed. Avoid using dividing lines, grids, and other embellishments within the data space. The epidemiologist must keep in mind that the primary purpose of a field investigation into an urgent public health problem is to control the problem and prevent further illness. Significant space–time clustering (assessed by the Knox test) of dengue cases in the city of Cairns, Australia, during January–August 2003. However, sometimes the population is unknown, costly to determine, or even inappropriate. Compute and plot rates for the smallest area possible. [1] Porta M, ed. Ongoing population surveys are important for understanding the prevalence of health risk behaviors in the general population. If you know both time of onset and time of the presumed exposure, you can estimate the incubation or latency period. Use other intervals (e.g., weeks or days) accordingly. The media can play important and sometimes conflicting roles during an outbreak. Electronic health records (EHRs) appear to be a promising newer source of data for public health surveillance and for assessing the prevalence of disease or behavioral risk factors in the population seeking healthcare (22). Information about determining whom to select is covered in study design discussions in Chapter 7, but sample size is worth briefly mentioning here. Information bias, such as measurement error, self-report bias, and interviewer bias. [Article in Italian] Parazzini F, Regallo M. PMID: 6427892 [PubMed - indexed for MEDLINE] MeSH Terms. New data may come by adding an ancillary … Text that highlights the main patterns of the data (this text might appear within the table or graphic or in the body of the report). However, it is important to consider conducting some preliminary data analysis even before data collection is complete. The data also helps healthcare agencies in assessing and forecasting the prevalence of diseases and ways to implement … The form collects information needed to monitor the status of screen- ing, reviewing and summarizing of each article by multiple reviewers. Cases of leptospirosis by week of hospitalization and rainfall in Salvador, Brazil, March 10–November 2, 1996. Participants were less likely to complete the Internet surveys. A second reason for students to have experience in data collection is that, sooner or later, they are likely to want to collect data of their own. In addition to the previously mentioned elements in common to all data displays (Box 6.2), tables have column and row headings that identify the data type and any units of measurement that apply to all data in that column or row. Because population estimates or censuses follow standard geographic areas (e.g., city, census tract, county, state, or country), determination of rates is also restricted to these same areas. < Previous Chapter 5: Using Technologies for Data Collection and Management, Next Chapter 7: Designing and Conducting Analytic Studies in the Field >. Contrast this with chronic diseases that can have exposures lasting for decades before development of overt disease. Good sample selection can help improve generalizability of results and ensure sufficient numbers of study participants. Public Health Problem: During April 2014–October 2015, residents of Flint, Michigan, were exposed to elevated lead levels in drinking water after the water source was switched from the Detroit Water Authority from Lake Huron to the Flint Water System (FWS) from the Flint River. Make sure overlapping plotting symbols are distinguishable. Cases can be plotted on a base map (Figure 6.13 [14]), a satellite view of the area, a floor plan, or other accurately scaled diagram to create a spot map. In contrast, if the public believes an outbreak resulted from eating a specific food item or eating at a specific restaurant, that belief can preclude the field epidemiologist’s ability to obtain accurate data after a press release has been issued because it might cause self-report bias among study participants. Similarly, prevalent case counts divided by the population from which they arose produce a proportion (termed prevalence). Recognizing disease patterns by personal attributes (e.g., age, sex, education, income, or immunization status) constitutes the fifth element in descriptive epidemiology. *Discontinued Resource by the GPO* Contains a collection of statistics (at the county, state, & country level) on social and economic conditions in the United States. Accordingly, less efficient and inaccurate displays, although common, were avoided or noted as not recommended. This expected or target case count is now corrected for the population and can be compared with the actual observed case counts. Minimize frames, gridlines, and tick marks (6–10/axis is sufficient) to avoid interference with the data. The best charts for quick and accurate understanding are dot plots, box-and-whisker plots, and simple bar charts. Footnotes that explain any abbreviations used, the data sources, units of measurement, and other necessary details or data. In compiling questions, consider the flow, needed skip patterns, and order (e.g., placing more sensitive questions toward the end). Determine Decisions Regarding Control Measure Implementation, Define The Investigation’s Objectives And Determine Data Needed, Multistate Outbreak Of Salmonella Typhimurium Infections Associated With Peanut Butter– Containing Products, 2008– 2009, Zika Virus Infection: An Emerging Vectorborne Disease, Environmental: Childhood Lead Poisoning And Drinking Water, Comparison Of Survey Methods In Norovirus Outbreak Investigation, Develop the Questionnaire or Survey Instrument, Calculate the Sample Size and Select the Sample, Review Legal Authority, Rules, and Policies Governing Data Collection, Issues and Challenges with Data Collection, Centers for Disease Control and Prevention. Examples of clinical data sources include medical record abstraction, hospital discharge data (e.g., for cases of hemolytic uremic syndrome) (15), syndromic surveillance systems (16) (e.g., for bloody diarrhea during an Shiga toxin–producing Escherichia coli outbreak) (17), poison control center calls (e.g., exposure to white powder during anthrax-related events) (18), and school and work absenteeism records (e.g., New York City school absenteeism in students traveling to Mexico at the beginning of the influenza A[H1N1] pandemic) (19). When comparing two graphs of the same dependent variable, use scaling that improves comparison and resolution. The collection of cancer incidence data used in the California Teachers Study was supported by the California Department of Public Health pursuant to California Health and Safety Code Section 103885; Centers for Disease Control and Prevention's National Program of Cancer Registries, under cooperative agreement 5NU58DP006344; the NCI's Surveillance, Epidemiology, and End Results … Collection of data on post environmental changes, such as climate or weather anomalies, natural disasters, ecological (flood, earthquake) or manmade conditions (war), helps the policymakers in assessing the potential to control and manage prevalence of infectious diseases. cDefined as current use of asthma medicine or one or more of the following symptoms during the previous 12 months: wheezing or whistling in the chest, awakening with a feeling of chest tightness, or attack of asthma. A rapid decrease in dengue cases follows this decrease in vector density. Epidemic curves for large geographic areas might not reveal the early periodicity or the characteristic increase and decrease of a propagated outbreak. To reveal distinctive internal patterns (e.g., by exposure, method of case detection, place, or personal characteristics) in time distributions, epidemic curves should be stratified (Figure 6.9). But we generally don’t enroll the entire population; instead we take samples. Some of the resources are collections or databases of data instruments, such as PROMIS or PhenX. Subsequent chapters discuss the details of data analysis. Response rate. By law, most states require laboratories that identify causative agents of notifiable diseases to send case information electronically to state public health agencies. To approximate the time of exposure, count backward to the average incubation period before the peak, the minimum incubation period from the initial cases, and the maximum incubation period from the last cases. Plot the rate, average, or total for each interval on a histogram or line graph. If the disease cause is unknown, this arrangement can assist the epidemiologist in developing hypotheses regarding possible exposures. Numbers are more easily compared down a column than across a row. These might include detailed administrative boundaries or a longitude-latitude grid. Aspect ratios (data space width to height) of approximately 2:1 work well. Thus, incidence divided by an appropriate estimation of the population yields several versions of incidence rates. Saving Lives, Protecting People. Align columns of numbers on the decimal point (or ones column). The rapid increase, plateau, and precipitous downslope all appeared with a salmonellosis outbreak from cheese distributed to multiple restaurants and then recalled (Figure 6.5). In 1951, the first conference of state epidemiologists determined which diseases should be nationally notifiable to the Public Health Service and later to CDC. Consider indicating the zero-level separately. Similarly, times of suspected exposures vary in their precision. A mixed mode of survey administration (e.g., mailed survey with phone follow-up) might be less expensive to conduct than a phone-only survey, but it also increases study complexity. If this means that you must exclude the zero level, exclude it, but note for the reader that this has been done. The predominant survey conducted in all states is the Behavioral Risk Factor Surveillance System, a random-digit– dialed household survey of noninstitutionalized US adults. You can use empirical cutoff points (e.g., BMI ≥26 for overweight). Control measures targeting the larva and adults of the mosquito vectors Aedes aegypti and A. albopictus began late in the first generation. Use alternatives to joining data points with a line. The range of public health control measures is broad (see Chapter 11). These distance associations of cases or rates are best understood on maps. Organize data by magnitude (sort) across rows and down columns. Use the table layout to guide the eye. The y-axis represents the rate of the health event. Distinguish between place of onset, place of known or suspected exposure, and place of case identification. Guidelines for Graphical Data Presentation, Characteristics of Propagated Epidemic Curves, Factors Affecting Patterns of Human–Vector–Human Transmission Across Time, Guidelines Regarding Data Display Area Of Epidemiologic Maps, Three General Interpretations of Age Distributions, Centers for Disease Control and Prevention. Instead, put them just outside the data region. During the same period, Dr. John Snow, known as the father of modern epidemiology, mapped deaths from cholera in London and determined the Broad Street Pump as the source of contaminated water (4). Date of onset of 185 cases of dengue in a fishing port: Guangdong Province, China, 2007. Data collection is defined as the ongoing systematic collection, analysis, and interpretation of health data necessary for designing, implementing, and evaluating public health prevention programs. They begin with a single or limited number of cases and increase with a gradually increasing upslope. Tables are commonly used for characterizing disease cases or other health events and are ideal for displaying numeric values. Additional existing data sources can help identify cases, determine background rates of human illness, or assess exposures to disease-causing agents (e.g., pathogenic bacteria, vectors, environmental toxins) in a field investigation. To develop effective prevention strategies, countries need to improve their information. For rates that vary more widely, a logarithmic scale for the y-axis is recommended for epidemiologic purposes (Figure 6.10) (10). In creating epidemiologic maps, you should follow certain basic guidelines (Box 6.9). 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