Step 3. Determine the Existence of an Outbreak Show
Establishing A Baseline For Confirming An Outbreak After the initial June 1981 Morbidity and Mortality Weekly Report of a cluster of cases of Pneumocystis pneumonia among men in Los Angeles, the ensuing investigation required approximately 6 months to establish surveillance and a baseline that confirmed the early phase of what eventually came to be known as the national epidemic of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS). Source: Adapted from References 10, 11. Determining the existence of an outbreak is a sometimes difficult step that should be completed before committing program resources to a full-scale investigation. This step also is necessary to rule out spurious problems (e.g., pseudoepidemics or reporting increases caused by surveillance artifacts). As noted previously, pseudoepidemics might result from real clustering of false infections (e.g., inadvertent contaminants of laboratory specimens) or artifactual clustering of real infections (e.g., increases in the number of reported cases because of changes in surveillance procedures introduced by the health department or implemented by a healthcare delivery system) (9). Problems potentially associated with pseudoepidemics include risks related to unnecessary or inappropriate treatment and unnecessary diagnostic procedures. To confirm the existence of an outbreak, the field investigation team must first compare the number of cases during the suspected outbreak period with the number of cases that would be expected during a nonoutbreak timeframe by
For certain problems, an outbreak can be rapidly confirmed through use of existing surveillance data. For others, however, substantial time lags might occur before a judgment can be made about the existence of an outbreak (Box 3.3). Step 4. Identify and Count Cases Simple Versus Complex Case Definitions Example of a Simple Case Definition The 2007 Zika virus (ZIKV) outbreak in Yap used the following case definition: Case definition: A patient with suspected disease had acute onset of generalized macular or papular rash, arthritis or arthralgia, or nonpurulent conjunctivitis during the period from April 1 through July 31, 2007. Case classification: We considered a patient to have confirmed Zika virus disease if Zika virus RNA was detected in the serum or if all the following findings were present: IgM antibody against Zika virus (detected by ELISA), Zika virus PRNT90 titer of at least 20, and a ratio of Zika virus PRNT90 titer to dengue virus PRNT90 titer of at least 4. A patient was classified as having probable Zika virus disease if IgM antibody against Zika virus was detected by ELISA, Zika virus PRNT90 titer was at least 20, the ratio of Zika virus PRNT90 titer to dengue virus PRNT90 titer was less than 4, and either no Zika virus RNA was detected by RT-PCR or the serum sample was inadequate for the performance of RT-PCR. Example of a Complex Case Definition Note how the case definition changed from 2007 as researchers learned more about ZIKV transmission. Laboratory Criteria for Diagnosis Recent ZIKV Infection
Recent Flavivirus Infection, Possible ZIKV
Epidemiologic Linkage
See Also Subtype Case Definitions
Source: Adapted from Duffy MR, Chen TH, Thane Hancock W, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med 2009;360:2536–2543; and Centers for Disease Control and Prevention. National Notifiable Disease Surveillance System (NNDSS). Zika virus disease and Zika virus infection, 2016 case definition. https://wwwn.cdc.gov/nndss/conditions/zika/case-definition/2016/06/. The aim of this step is to identify, or ascertain, as many cases as possible without including noncases. As a practical matter, this entails casting a broad net through use of a classification scheme—the case definition (see the following discussion)—that maximizes sensitivity (i.e., correctly identifies persons who have cases of the condition [true-positives]) and optimizes specificity (i.e., does not include persons who do not have cases of the condition [false-positives]) (see Box 3.4). The case definition is a statement consisting of three elements that together specify a person
Although the case definition might be broad at the onset of an epidemiologic field investigation, it is a flexible classification scheme that often is revised and narrowed as the investigation progresses. To minimize the likelihood of ascertainment bias (i.e., a systematic distortion in measurement due to the way in which data are collected), cases ideally are sought and counted through systematic searches of a multiplicity of potential sources to identify the maximum number, or a representative sample, of cases. Examples of sources include
Information about identified cases (e.g., coded patient identifiers, age, sex, race/ethnicity, date of illness onset or diagnosis, symptoms, signs, laboratory findings, or other relevant data) should be systematically recorded in a spreadsheet or through other means (e.g., a line listing or similar epidemiologic database) for subsequent analysis and for use in conducting further investigative studies (e.g., hypothesis testing). All staff involved in data collection and maintenance should be trained to use the forms and questionnaires (whether these be on paper or electronic) and to store the forms to protect personal information while facilitating rapid data analysis. Depending on the nature, scope, and extent of the outbreak, consideration should be given to the need for additional active case finding and surveillance once sufficient information has been collected to support prevention and control efforts. Specifically, ongoing or intensified surveillance can be paramount in subsequent efforts to evaluate the effectiveness of control measures for curbing and terminating the epidemic (see Step 9). Step 5. Tabulate and Orient the Data in Terms of Time, Place, and Person This step involves translating and transforming data from the line listing into a basic epidemiologic description of the outbreak. This description characterizes the outbreak in terms of time, place, and person (referred to as descriptive epidemiology). Through systematic review of data in the line listing, key actions typically involve
In addition, these key actions contribute to developing initial hypotheses for explaining the potential cause, source, and mode of spread of the outbreak’s causative agent(s). Time Establishing the time of the outbreak or epidemic requires the following actions:
Chapter 6 includes examples of epidemic curves displaying the types of information that can be analyzed to aid in conducting a field investigation.
Place Use information collected for the line listing and through other inquiry to orient cases in relation to locations, including
Using information about place, construct spot maps (Figures 3.1, 3.2, 3.3) or other visual methods to depict locations of cases at time of onset of illness or possible exposure to causal agents or factors, including
Person Use information collected for the line listing to describe cases in relation to such factors as
When possible and where indicated, obtain denominator data (e.g., total cook-out attendees in a foodborne disease outbreak) to develop preliminary estimates of rates of illness in relation to demographic, exposure, and other characteristics. Which of the following must be created before establishing the evaluation plan for a health project?13. What must be created before establishing the evaluation plan to determine the success (or lack of) for a health project? Goals are generally what is desired, while observable and measurable objectives are used to determine whether or not the goal was achieved and whether the project was successful.
Which of the following best describes when a community health nurse would try to collect data on a health issue?Which of the following best describes when a community health nurse would try to collect data on a health issue? Formal data collection does not exist for all health data. Therefore, many nurses must perform additional data collection, compilation, and analysis.
What best describes why is it important for nurse Rosemary to be knowledgeable about the community when providing care to Individuals?Which best describes why it is important for the nurse to be knowledgeable about the community when providing care to individuals? Individuals and families are strongly influenced by the community and environment around them.
Which task would the nurse complete first?-The first action the nurse should take when using the nursing process is to collect data from the client. By identifying the client's concerns and reasons for refusing the medications, the nurse can determine which actions to take next to prevent worsening of the client's condition.
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Which of the following actions must a nurse take to be successful in addition to the typical assessment diagnosing and planning directly related to the intervention project?
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