What Are Contributing Factors?

Contributing factors are food preparation practices that lead to food getting contaminated with germs, or that lead to germs growing in food. Environmental health and food safety staff can find contributing factors for outbreaks and help prevent future outbreaks.

What Are the Types of Contributing Factors?

There are 32 contributing factors. They fall into these 3 types:

• Contamination – when pathogens and other hazards get into food
• Proliferation – when pathogens in food grow
• Survival – when pathogens survive a process to kill or reduce them

What Are the Most Common Contributing Factors for Outbreaks in Restaurants?

The top contributing factors for outbreaks in restaurants are:

• When a sick food worker contaminates ready-to-eat food through bare-hand contact.
• When a sick food worker contaminates food through a method other than hand contact (such as with a utensil they contaminated)
• When a sick food worker contaminates ready-to-eat food through glove-hand contact.
• When food handling practices lead to growth of pathogens (such as food not kept cold enough)

What Is the Role of Environmental Health and Food Safety Staff?

Environmental health and food safety programs can work to identify contributing factors for all foodborne illness outbreaks. Investigators should:

• Use their knowledge about the germ linked to the outbreak to guide their environmental assessment.
• 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.

Where Can I Learn More About Contributing Factors?

For more on contributing factors, explore the following resources:

• Contributing Factors: Preventable Causes of Foodborne Illness (infographic)
• Contributing Factor Definitions (list of all 32 contributing factors)
• E-Learning on Environmental Assessment of Foodborne Illness Outbreaks (training)
• Factors that Contribute to Outbreaks of Foodborne Illness (summary of scientific article)
• Outbreak Characteristics Associated with Identification of Contributing Factors to Foodborne Illness Outbreaks [PDF – 202 KB] (scientific article)