PUB 540 Discuss the steps involved in an outbreak investigation

PUB 540 Discuss the steps involved in an outbreak investigation

PUB 540 Discuss the steps involved in an outbreak investigation

A disease outbreak/epidemic is the occurrence of cases of disease in excess of what would normally be expected in a defined community, geographical area or season. (Dr. Aruba Rastogi 2019)

An outbreak/epidemic may occur in a restricted geographical area, or may extend over, several neighboring areas, whole country or several countries. It may last for a few days or weeks, or for several years.

Most local health departments investigate an apparent outbreak when the number of affected (or exposed) persons is large, when the disease is severe (serious illness with high risk of hospitalization, complications, or death), when effective control measures exist, and when the outbreak has the potential to affect others unless prompt control measures are taken.

At the state or national level, the unusual presentation of disease may spur an investigation.

Occurrence of a new or rare disease or a change in the pattern of disease in an area is more likely to prompt an investigation than occurrence of a common disease with well-established transmission patterns and control measures.

Once the decision to conduct a field investigation of an acute outbreak has been made, a systematic approach ensures that the investigation proceeds without missing important steps along the way. ( Dr Aruba Rastogi 2019 )

Prepare for field work

Investigator should be well prepared to conduct a field investigation before leaving for the field regardless of when the decision to conduct a field investigation is made.

Establish the existence of an outbreak

To establish the existence of an outbreak, the observed number of cases is compared with the expected number for a certain place or time period.

Verify the diagnosis/ ensure proper diagnosis of reported cases

Verifying the diagnosis is closely linked to verifying the existence of an outbreak. This is important: (a) to ensure that the disease has been properly identified, since control measures are often disease-specific; and (b) to rule out laboratory error as the basis for the increase in reported cases.

Define and identify cases

A case definition is constructed for the identification of cases. It is a standard set of criteria for deciding whether an individual should be classified as having the health condition of interest. A case definition includes clinical criteria (signs and symptoms) and restrictions by time, place, and person. The criteria must be applied consistently to all persons under investigation.

Perform descriptive epidemiology

In an outbreak situation, cases that prompt the concern are often only a small and do not represent the total number of cases. Therefore, with the help of public health workers, investigator must look for additional cases to determine the true geographic extent of the problem and the populations affected by it. All the cases should be counted as reported by either passive surveillance (patient coming directly to health facility) or reported by active surveillance (health worker searching for the cases)

PUB 540 Discuss the steps involved in an outbreak investigation
PUB 540 Discuss the steps involved in an outbreak investigation

Develop hypotheses

The descriptive epidemiology may provide useful clues that can be turned into hypotheses. In an outbreak context, hypotheses are generated in a variety of ways. First, consider what is known about the disease itself: What is the agent’s usual reservoir? How is it usually transmitted? What vehicles are commonly implicated? What are the known risk factors?

Evaluate hypotheses

After a hypothesis that might explain an outbreak has been developed, the next step is to evaluate the plausibility of that hypothesis. Typically, hypotheses in a field investigation are evaluated using a combination of environmental evidence, laboratory science, and epidemiology. From an epidemiologic point of view, hypothesis is evaluated in one of two ways: either by comparing the hypotheses with the established facts or by using analytic epidemiology to quantify relationships and assess the role of chance.

Communicate findings

The final task is to summarize the investigation, its findings, and its outcome in a report, and to communicate this report in an effective manner. An oral briefing for local authorities and a written report that follows the usual scientific format of introduction, background, methods, results, discussion, and recommendations should be send to concerned authority.

Implement control and prevention measures

In most outbreak investigations, the primary goal is control of the outbreak and prevention of additional cases. In practice control and prevention activities are implemented as early as possible.

Follow up recommendations/ maintain surveillance

Once control and prevention measures have been implemented, outbreak situation should be monitored. Active surveillance should be continued as is essential for:

Deciding if outbreak is over and for this surveillance may be continued for at least two incubation periods of concerned disease following onset in the last case. Documenting effectiveness of control measures

Reference :

Dr. Aruna Rastogi : Mar 01, 2019

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Friis & Sellers (2021) discuss the process that Dr. Snow used in tracing the origin of cholera in 1854. The text lays out five major steps in investigating a disease outbreak. The steps are as follows: 1) define the problem as an actual outbreak in the community or potentially caused by a physiologic problem, the importance of getting this right is that this will cut down on time related to finding the origin of the outbreak; 2) evaluate the problem for what it is as compared to other events associated with a certain, time, place or person is important to determine where most cases are occurring, how long people after exposure are people getting sick, and also to allow testing of bodily waste to determine the cause; 3) come up with a working theory as to what is causing the problem, so that if you can figure out the cause, you then can come up with a way to control the outbreak as well ; 4) test the hypothesis by ruling out certain causes and come up with alternative causes to make sure the correct causes has been determined; and 5) based on the evidence at hand, draw conclusions as to the cause and put in place interventions to mitigate and potential cure the problem for long-term tracking and long-term control measures. 

Webber, R. (2020) describes an outbreak as any time there are excessive deaths, unexplained clusters of disease presentation, excessive cases of disease in the population, there may be an outbreak of disease. The author describes steps that are both rational for each step and description together. Where treatment for the causes and interruption of transmission takes place together by the same interventions depending on the cause of the outbreak. 


Friis, R. H., & Sellers, T. (2020). Epidemiology for public health practice (6th ed.). Jones & Bartlett Learning. 

Webber, R., (2020). 4.1 investigation of an outbreak. Communicable diseases: a global perspective (6th ed.). CABI. Credo Reference: 

An outbreak is defined as a localized disease epidemic in a specific place such as a healthcare facility or a city ( Friis & Sellers, 2021). An outbreak investigation is conducted to collect information about the cause or source of disease and to prevent more people from getting infected. Outbreak investigation steps are the systematic procedures to properly study the origin of a disease and identify solutions. The following are the steps for outbreak investigation:

1.      Prepare for the field – This is the step when researchers gather equipment and tools needed for investigation and make arrangements for the local community and identify protocols to follow.

2.      Establish the existence of an outbreak – This step determines the severity of the outbreak, potential threat, how it spread, and any public concerns.

3.      Verify the diagnosis- This procedure ensures that no lab errors such increase of cases due to experimental error. It verifies procedures that identified the problem.

4.      Construct a working case definition- Case definition is the criteria that determine if an individual has the health condition of concern.

5.      Find cases systematically and record information- This procedure is conducted by public health workers to identify the extent of the outbreak by identifying individuals affected by the outbreak.

6.      Perform descriptive epidemiology – This step is crucial during the investigation as it provides a characterization of the outbreak.

7.      Develop hypotheses – Hypotheses helps provides solutions to many questions regarding the outbreak.

8.      Evaluate hypotheses epidemiologically – This procedure validates the hypotheses through lab verification and comparison of established facts.

9.      As necessary, reconsider, refine, and re-evaluate hypotheses -This is conducted when hypotheses cannot be confirmed during analytical studies. Therefore, there may be the need to look for a new mode of transmission and be more specific in makeup controls and case patients.

10.  Compare and reconcile with laboratory and/or environmental studies -1.      Laboratory are environmental studies are both important in explaining how an outbreak has occurred. Laboratory validates finding while environmental studies is helpful in identifying environmental conditions.

11.  Implement control and prevention measures – This procedure is critical in stopping the spread of the disease by interrupting the chain of transmission and preventive measures such as immunization.

12.  Initiate or maintain surveillance- It is a critical step to ensure the implemented preventive measures are effective by monitoring.

13.  Communicate findings – This is another important step as it provides essential information for future reference, legal issues, and education through written reports.


Center for Disease Control and Prevention. (n.d.) Lesson 6: Investigating an outbreak, Section 2: Steps of an Outbreak Investigation. Retrieved from

Friis, R.H. & Sellers, T.A. (2021). Epidemiology for public health practice (6th ed.). Burlington, MA: Jones & Bartlett Learning.

When it comes to outbreaks within the community investigations are very influential, as they assist the healthcare professionals in learning more about the cause and outbreak of the disease. The investigations can mark the cause and provide the knowledge to the community. In order to control an outbreak and prevent additional illnesses it is important to recognize infections/ occurrences of the diseases and follow the appropriate steps. According to English, L (2017). The steps go as followed: Identify investigation team and resources, establish existence of an outbreak, verify the diagnosis and obstruct case definition, find cases systematically and develop line listing, Perform descriptive epidemiology/develop hypotheses, Evaluate hypotheses/perform additional studies as necessary and Implement control measures.

In step one , it’s important have the group of resources at a State and local level to allocate all consults and specialist to respond to appropriately, next establish the outbreak, this is important as this allows the investigators to get a sense of the true magnitude of the outbreak. Establishing the existence of an outbreak ,verify the diagnosis and obstruct case definition all assist the investors in identifying the characteristic of the illness including risk factors and cause. In finding cases systematically and develop line listing assist in gathering clinical data i.e.; Symptoms, onset dates and time, exposure information and demographic info. In performing descriptive epidemiology the primary focus is on person, place and time including the EPI curves which suggest the time & type of exposure . Next step is to Evaluate hypotheses/perform additional studies as necessary and Implement control measures during this stage of the investigation the focus is on studying the types, exposures equally among both ill and non-ill, exposures and in the control measures the aim is to prevent further diseases and encouraging isolation and all measures to control the outbreak (Moore, 2018). Following the proper steps during an outbreak investigation can assist the public health departments in allocating all the necessary resources and protect the community


L’Tanya, E (2017). Outbreaks and Infection Emergencies. Retrieved from:

Moore, Z,(2018).Outbreak Investigations: The 10-Step Approach. Retrieved from

An outbreak is a sudden increase in the number of cases of a health risk such as pathogenic agents, transmissible diseases, or infections (Houlihan & Whitworth, 2019). Outbreaks record a higher number of cases compared to the normally expected number. Outbreaks are similar to epidemics but are limited to a smaller geographical area. Outbreak investigation refers to a process of scrutinizing a new disease aiming to identify the cause, mode of transmission, and prevalent populations (Houlihan & Whitworth, 2019). The investigation process enables epidemiologists to identify relevant factors used in developing potentially effective treatment and preventive measures. According to Houlihan and Whitworth (2019), the steps involved in an outbreak investigation are as follows:

Step 1: This step involves establishing the presence of an outbreak (Houlihan & Whitworth, 2019). Healthcare providers can report unusual and unexpected presentations. For instance, caregivers can identify a disease outbreak after attending to a cluster of patients from a similar location presenting with unusual symptoms. Surveillance systems help monitor populations for early detection of outbreaks.

Step 2: Verifying the diagnosis

This step is significant in identifying disease pathogens. Samples are transported to laboratories for RNA and DNA amplification in cases where standard diagnostic tests are unsuccessful.

Step 3: Making a definition

This step is essential in ensuring cases are not missed. Despite the complexity of defining cases when diseases have non-specific symptoms, real-time analysis of case definitions helps capture all cases.

Step 4: Finding cases

This step involves the use of paper forms and electronic data-entry platforms to list, locate, and follow up on outbreak cases and contacts.

Step 5: Rapid diagnostic tests

Rapid diagnostic tests are significant in the quick identification of cases.

Step 6: This step involves the improvement of health systems by the provision of adequate resources, and improving laboratory systems, diagnostics, and treatment techniques.

Step 7: Descriptive epidemiology and hypothesis testing

Hypothesis testing is significant in confirming the origin of an outbreak. Descriptive epidemiology helps define the population at risk, its geographical location, and the specific time of outbreak onset.

Step 8: Control measures and communication aiming at mitigating the disease outbreak.


Houlihan, C. F., & Whitworth, J. A. (2019). Outbreak science: Recent progress in the detection  and response to outbreaks of infectious diseases. Clinical Medicine (London, England)19(2), 140–144.

The steps that are involved in an outbreak investigation is making sure we prepare for the field work. Doing the field work something to investigate before you go ahead and make any accounting for the increase for the disease of the outbreak. For the the field work to run smooth make sure that the Public health workers have everything they need to investigations. For me as a Enviromental Health worker I have to make sure I have all my testing kits for pools, and kits for the kitchen for establishments that includes, gloves. masks, flash light, zip lock bags in case of something abnormal i can take and seal. The second step is the establish the existence of an outbreak. An epidemic or an outbreak is repetitive of more cases than expected. Another one I can use is my job if I get a complaint on a establishment of food borne illness. I have 24 hours to investigate the problem. I would check certain foods that the complaint said got them sick and I will investigate the temperatures and the reheating and the contamination. Another thing is I get a number, a large number of people I will go ahead and see where that outbreak came from thats why its so important to see what foods where given and how fast they got sick, because there is certain bacterias that grow and get people sick and there is a time frame for them to develop and get them sick. The third step is to verify the diagnosis. This step is very important because we to make sure the diseases is properly identified. Step four is construct a working case definition deciding whether an individual should be classified as having the health condition of interest.