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How Environmental Health Specialists Investigate Outbreaks

This page shows the study purpose, method, results, conclusions, and recommendations in plain language for the EHS-Net project titled Environmental Health Specialists’ Self-Reported Foodborne Illness Outbreak Investigation Practices.

The findings and recommendations from this project are also in fact sheet format [PDF - 310 KB].

Citations for more EHS-Net publications are available by Study Topic or by Citation.

Photo of a specialist taking food temperature.

Study Problem

Knowing the contributing factors to foodborne illness outbreaks is critical to stopping them. Environmental health specialists find contributing factors by investigating outbreaks. But these investigations often do not give enough information. This may be the result of ineffective investigation practices and problems faced during investigations. Thus, it is important to collect data that will describe investigation practices and problems.

Study Purpose

The purpose of this study was to describe how environmental health specialists investigate foodborne illness outbreaks. This study also looked at problems faced by specialists during these investigations.

Study Findings in Brief

EHS-Net found that environmental health specialists dealt with the following problems during foodborne illness outbreak investigations:

  • Uncooperative restaurant workers.
  • Uncooperative restaurant customers.
  • Organizational problems such as lack of management support and training.

Study Method


Forty-two specialists took part in the study. They worked in state or local public health departments in the 2004 EHS-Net sites.

Data Collection

We talked to six focus groups. In each group, the study leader asked questions of five to eight specialists. The questions were about

  • Outbreak investigation practices.
  • Methods used to find outbreak contributing factors (such as environmental causes of outbreaks, or sick workers handling food).
  • Problems faced when investigating outbreaks.

Study Results

Outbreak Investigation Practices

Some specialists said they did routine inspections during outbreak investigations. But many said their visits to restaurants during outbreaks were different from their routine inspections. During an outbreak, they focused more on four activities. These activities are recommended by the Food and Drug Administration:

  • Finding the food linked to the outbreak.
  • Learning how the food linked to the outbreak was handled.
  • Learning how foods linked with foodborne illness in general are handled.
  • Talking to workers to find those who might be ill.

Many said they worked with epidemiology staff. How they worked together varied.

Methods Used to Find Contributing Factors

Finding contributing factors was hard. Specialists were often not able to find them.

Many specialists said they focused more on learning the germs that caused the outbreak than on finding contributing factors.

Finding contributing factors often depended on finding the food and/or germ linked to the outbreak.

The germ, food, and contributing factors were found by

  • Looking at illness symptoms.
  • Carrying out epidemiologic analyses.
  • Doing restaurant investigations.

Three things made it hard to find contributing factors:

  • Turnover of restaurant workers.
  • Restaurant workers who did not cooperate.
  • Time lags between outbreaks and investigations.

Problems Faced When Investigating Outbreaks

Specialists talked about 12 problems of investigations. Problems fell into four groups.

  • Restaurant workers who did not cooperate.
  • Restaurant customers.
    • Trouble contacting them to ask them about their illness and what they ate.
    • Lack of cooperation. Some did not want to talk about symptoms or give stool samples.
    • Trouble finding out what they ate. Some could not remember.
    • Lack of knowledge about foodborne illness. Specialists had to teach customers before their questions could be answered.
  • Public health agency.
    • Lack of epidemiologic help or a team approach.
    • Lack of training and experience investigating outbreaks.
    • Lack of support from management.
    • Lack of teamwork between state and local agencies.
    • Lack of staff to conduct investigations.
  • Other.
    • Lack of cooperation from doctors. They did not always test patients with illness symptoms when asked.
    • Delay in investigations because sick people were slow to tell agencies about illnesses.

Study Conclusions

Some specialists said they only did routine inspections during investigations. But many said their visits to restaurants during outbreaks were different from routine inspections. During these visits they focused on

  • Finding the food linked to the outbreak.
  • Learning how that food was handled.
  • Talking to food workers to find those who might be sick.

Many specialists said they did not often find outbreak contributing factors during investigations. Many said they focused more on learning which germs caused the outbreak than on finding the contributing factors.

Specialists discussed several investigation problems. These included problems linked with

  • uncooperative restaurant workers.
  • uncooperative restaurant customers.
  • organizational issues in public health agencies.

Some specialists reported a lack of help from and teamwork with epidemiology staff.

EHS-Net Recommends

Outbreak investigators should conduct activities that are more likely to lead to finding outbreak contributing factors.

Investigators should visit restaurants early in investigations. Workers may be more likely to cooperate in the early stages.

Education programs may help restaurant customers learn about foodborne illness.

Doctors could learn more about foodborne illness diagnosis and investigation. The Centers for Disease Control and Prevention primer on foodborne illness could be a helpful tool.

The role of environmental health in outbreak investigations should be defined. This is needed so that epidemiology and environmental health programs work together. This could also help with problems posed by public health agencies (for example, lack of support from management).

Key Terms

  • Contributing factors: conditions that contribute to foodborne illness. For example, a food worker handles food while sick and passes germs from his hands to the food he is making.
  • Environmental health specialists: public health workers who enforce health and safety standards related to food and other consumer products. They conduct restaurant inspections.
  • Epidemiology: study to describe risk factors for sickness and what caused sickness.
  • Focus groups: groups of environmental health specialists who were asked about what made it easier or harder to handle food safely.
  • Foodborne illness outbreak: when two or more people have the same sickness after eating food from the same place.
  • Inspection: regular visit to see how well restaurants follow local food safety rules.
  • Outbreak investigation: activities to find out what caused an outbreak.
  • Stool sample: Fecal matter collected for analysis.
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