What Are Contributing Factors?
Contributing factors are preventable causes of outbreaks.
Contributing factors are the practices and factors that lead to outbreaks. In an outbreak, contributing factors are the “how” and root causes are the “why.”
Identifying contributing factors in foodborne illness outbreaks can help stop them and prevent them in the future.
Watch our short training video on contributing factors, From Inspector to Investigator: Finding the Factors that Lead to Foodborne Outbreaks
Contributing factors fall into 3 types.
Pathogens and other hazards get into food.
For example, a sick food worker handles food with their bare hands.
Pathogens already in food grow.
For example, food held at the wrong temperature for a long time can allow harmful bacteria to grow.
Pathogens survive a process to kill or reduce them.
For example, food is not cooked long enough or to a hot enough temperature.
The most common contributing factors for outbreaks in restaurants come from sick food workers and food preparation practices.
Sick food workers can contaminate ready-to-eat food when they come into work while experiencing symptoms, such as vomiting or diarrhea. Food workers who are infectious can contaminate food:
- with bare hands
- while wearing gloves
- in other ways, such as letting food touch a contaminated cutting board or utensil
Improper food preparation practices are another common contributing factor for restaurant outbreaks. Not cooking food to a hot enough temperature and other improper food preparation practices can lead to pathogens growing.
Environmental health and food safety programs can take action to identify contributing factors for foodborne illness outbreaks.
They can
- Take CDC’s free, interactive training on conducting environmental assessments to improve their ability to identify contributing factors and their underlying root causes.
- Conduct an environmental assessment as soon as they learn of a potential outbreak.
- Use epidemiologic and laboratory data to guide the environmental assessment.
- Report contributing factors to CDC’s National Environmental Assessment Reporting System (NEARS).
The environmental assessment component of outbreak investigations helps identify contributing factors.
Environmental assessment activities include
- interviewing kitchen managers and food workers,
- observing how food is prepared,
- reviewing or collecting records (for example, records of food cooking temperatures, traceback records), and
- sampling for pathogens in the restaurant kitchen.
What else can food programs do?
State and local food regulatory programs can
- Join NEARS to provide critical information for their program and to inform national food safety efforts.
- Use the FDA Food Code as the model for regulation of restaurants and retail food establishments.
Data reported to NEARS showed that
Investigators were more likely to identify an outbreak’s contributing factors if
- They knew the pathogen linked to the outbreak,
- They scheduled their assessment visit to the establishment within a day of learning about the outbreak,
- They made multiple visits to the outbreak establishment to complete their assessment,
- the outbreak establishment prepared all meals on-site, and
- the outbreak establishment served more than 150 meals daily.
Read more: Factors that Contribute to Outbreaks of Foodborne Illness (summary of Brown LG, Hoover ER, Selman CA, Coleman EW, Rogers HS. Outbreak characteristics associated with identification of contributing factors to foodborne illness outbreaks. Epidemiol Infect. 2017;145(11):2254-62)
Want More Information?
Explore the following resources:
- From Inspector to Investigator: Finding the Factors that Lead to Foodborne Outbreaks (quick training video)
- Contributing Factors: Preventable Causes of Foodborne Illness (infographic)
- Contributing Factor Definitions (list of all 30 contributing factors)
- Root Causes of Outbreaks (resources on identifying root causes)
- Environmental Assessment Training Series (EATS) (training)
Additional articles on contributing factors:
- Factors that Contribute to Outbreaks of Foodborne Illness (summary of scientific article)
- Modernizing the Foodborne Outbreak Contributing Factors: the Key to Prevention (column about the 2020 revision process)
- Outbreak Characteristics Associated with Identification of Contributing Factors to Foodborne Illness Outbreaks (scientific article)