Outbreak Data on Contributing Factors

At a glance

Find out when contributing factors were more likely to be identified for nearly 300 foodborne illness outbreaks. Environmental assessments are key to identifying these factors.

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Key takeaways

To identify foodborne illness outbreak contributing factors,A investigators should

  • Use their knowledge about the germ linked to the outbreak to guide their environmental assessment.B
  • Conduct their assessment as soon as they learn of a potential outbreak.
  • Conduct a complete assessment that may require multiple visits to the outbreak establishment.

To improve their ability to identify contributing factors, investigators can take CDC's free, interactive training on conducting environmental assessments.

Why this is important

Each year, more than 800 foodborne illness outbreaks occur in the United States. Data on contributing factors to outbreaks are critical to outbreak prevention, and environmental assessments identify contributing factors.

Environmental health and food safety program staff conduct these assessments during outbreak investigations. But, we don't know a lot about how to help investigators identify contributing factors. The purpose of this project was to learn more about outbreak traits linked with identifying contributing factors.

What we learned

Contributing factors were identified in 3 out of every 5 outbreaks (194 of 297) reported to CDC's National Environmental Assessment Reporting System (NEARS). Contributing factors were more likely to be identified for outbreaks if:

  • The germ linked to the outbreak was known
  • The outbreak establishment prepared all meals on-site
  • The outbreak establishment served more meals daily
  • Investigators quickly (within a day of learning about the outbreak) contacted the establishment thought to be linked with an outbreak to schedule their assessment visit and
  • Investigators made multiple visits to the outbreak establishmentC to complete their assessment

Timely and complete outbreak assessments are important to identifying contributing factors. These findings highlight the need for strong environmental health and food safety programsD with the capacity to complete such assessments.

More information

Journal article this plain language summary is based on

About this study‎

This study assessed outbreak data reported to the National Environmental Assessment Reporting System (NEARS). Local, state, tribal, and territorial programs use NEARS to report environmental assessment data. These data come from foodborne illness outbreak investigations in restaurants, banquet facilities, schools, and other institutions.
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Content Source:
National Center for Environmental Health
  1. Contributing factor: Food preparation practices that lead to food getting contaminated with germs, or that lead to germs surviving and growing in food; for example, food not being cooked at a hot enough temperature to kill germs.
  2. Environmental assessment: Part of the outbreak investigation describing how and why the environment contributed to germs getting in and spreading to make people sick.
  3. Outbreak establishment: An establishment that has been linked with a foodborne illness outbreak; for example, several people with a foodborne illness all report eating the same food at the same restaurant.
  4. Environmental health and food safety programs: Public health programs responsible for ensuring environmental health and food safety; staff in these programs are typically responsible for inspection restaurants and conducting environmental assessments during foodborne illness outbreak investigations.