Cookie Dough or Cookie No?

Introduction

Public health surveillance is used to detect outbreaks in the United States. When outbreaks happen, state, local, and territorial health departments can ask for assistance from the Centers for Disease Control and Prevention (CDC) to identify the cause of the outbreak and control the spread. CDC works in partnership with local, state, and territorial health departments and with other federal agencies to protect the nation's public health.

According to the constitution, public health concerns are to be handled by state, local and territorial public health agencies, often called health departments. When the state health department requires additional resources and support, they can request assistance from the CDC. CDC is the federal public health agency for the United States. CDC is considered an advisory agency meaning the CDC provides assistance and scientific support to the investigation, but cannot make or enforce regulations, such as imposing recalls. CDC and the states rely on partnerships with regulatory agencies, including the Food and Drug Administration (FDA) and the US department of Agriculture (USDA), to develop and enforce regulations, and impose recalls.

CDC Disease Detectives

When an outbreak occurs and a state or territorial health department requests assistance, CDC's Epidemic Intelligence Service (EIS) officer, or disease detectives, often respond. EIS is a longstanding internationally-recognized fellowship program, renowned for its investigative and emergency response efforts.

Investigating Outbreaks

When an outbreak occurs disease detectives and other public health officials follow a set of steps to investigate. The steps listed below in Figure 1 are an example of one set of steps used to solve an outbreak. There can be some variation in these steps.

It is important to know that the steps of an outbreak investigation are meant to serve as a guideline. In many cases disease detectives do not follow the steps in order. For example, when we know that there is a serious illness, but we do not know the exact cause we still may want to share as much information with the public as possible so that they may protect themselves.

It is important to note that we will be talking about the source of an outbreak. When the word source is used, we are talking about the source of contamination (e.g., food manufacturing plant or petting zoo). When we use the word pathogen, we are referring to the strain of Escherichia coli (E. Coli) causing the illness.

Figure 1: Steps in an Outbreak Investigation

Steps in an Outbreak Investigation

Prepare for fieldwork
Establish the existence of an outbreak
Verify the diagnosis
Construct a working case definition
Find cases systematically and record information
Perform descriptive epidemiology
Develop hypotheses
Evaluate hypotheses epidemiologically
Reconsider, refine, and re-evaluate hypotheses.
Implement control and prevention measures
Initiate or maintain surveillance
Communicate findings

In this outbreak scenario PulseNet was used to identify several of the early cases. PulseNet is a national laboratory network that connects foodborne illness to detect outbreaks. PulseNet uses DNA fingerprinting of bacteria making people sick , to detect thousands of local and multistate outbreaks. Since the network began in 1996, PulseNet has improved our food safety systems through identifying outbreaks early. This allows investigators to find the source, alert the public earlier, and identify gas in food safety systems that would not otherwise be recognized.

This activity is based around a multi-state E.Coli outbreak that occurred in 2009 and was eventually linked to a specific product. While some of the data presented may not be the exact data that occurred in that outbreak, the basic facts of the outbreak are the background of this activity.

Communication during an outbreak

Communication is an important part of any outbreak investigation because outbreaks can cause panic among citizens, and because citizens need information to make informed consumer decisions. In this lesson, students will work to carefully craft messages to target populations once the outbreak source has been identified.

Public health agencies generally do not make public statements about foodborne illness outbreaks unless there is an action that the public can take. In doing this, the public health agencies don't induce panic in the public and avoid economic damage to a company that might appear to be connected to the outbreak initially but is later eliminated as a source of the outbreak. In this activity, you can highlight this idea because you are not asked to craft a public message until the source of the outbreak has been identified.

CDC's Emergency Operations Center

When outbreaks cross state lines and become large enough to necessitate additional money, people, and resources, CDC may choose to activate the Emergency Operations Center (EOC). The EOC is a place where highly trained experts monitor information, prepare for known (and unknown) public health events, and gather in the event of an emergency to exchange information and to make decisions quickly. Even when there is no specific public health threat, the EOC has dedicated staff monitoring information, helping to keep us safe 24/7.

During an EOC activation, disease detectives, or epidemiologists among other staff are called in to respond. It is important to note that EOC activation typically occurs for larger response efforts (E.G., Zika, Ebola, polio), this lesson simulates the activation of the EOC for educational purposes.

Odds Ratio

This scenario models a case-control study. In a case control study, the epidemiologist gathers data about case-patients (individuals with condition of interest) and controls (individuals with similar demographics as the cases, but without the condition of interest). You can think of cases as people who are sick and controls as people who are not sick . In this simulation, cases are individuals who meet the case definition (A person residing in the United States, with bacterial isolate matching the outbreak strain E.Coli O157:h7, with illness onset between February 15, 2009 to July 15, 2009). Controls would be people who did not have this strain of E.coli with illness onset coinciding with the dates above. Controls should be individuals who are similar to the case-patients. Epidemiologists try to match based on sex, race/ethnicity, age, and other demographics.

Once the epidemiologists identify cases and controls, they gather exposure data and calculate odds ratios. Exposure data is any potential source of the E. coli O157:h7 infection. This would include exposure to certain food and animals because they would be the pathogen host.

Odds ratios provide a measure of how much higher the odds of exposure are among cases as compared to contgrols. Odds ratios are calculated for each item of exposure for which data is collected. This might include specific food products (eggs, milk, peanut butter), specific brands, specific locations visited, etc. Odds ratios can be interpreted as follows:

An OR of 1.0 means the odds of exposure among case-patients is the same as the odds of expsure among controls. This means the exposure is not associated iwth the disease.
An OR greater than 1.0 means the odds exposure among case-patients is greater than the odds of exposure among controls. This means the exposure is possibly the cause of the disease.
An OR less than 1.0 means the odds of exposure among case-patients is lower than the odds of exposure among controls. This means the exposure might be a protective factor against the disease.

Odds raiots are, in theory, the odds of exposure for cases divided by the odds of exposure for controls. Odds' ratios can be a tricky concept in Epidemiology.

It is helpful no build a 2x2 table when calculating OR. The exposure in this outbreak will be the food items of interest (tomatoes, cookie dough, etc.). The disease of interest is E.coli O157:h7.