Root Causes of Outbreaks
Outbreak investigators can identify root causes to help stop outbreaks.
Root causes are the reasons outbreaks occur. Root causes of outbreaks are sometimes called environmental antecedents. Identifying root causes can help determine the steps needed to stop the outbreak and prevent future ones.
During an investigation of a restaurant outbreak, investigators look for evidence about what might have led to the outbreak. They then ask questions to narrow down potential root causes. For example, they might identify high staff turnover or a language barrier as a root cause of restaurant outbreaks.
Use our resources to identify root causes.
We have several resources to help investigators learn more about root causes and identify them:
- Root Causes Overview [PDF – 260 KB]: One-pager on the five types of root causes
- Field Guide to Identifying Root Causes [PDF – 876 KB]: Information on root causes for use during outbreak investigations
- Identifying Root Causes—A Reference for NEARS Users [PDF – 774 KB]: In-depth reference manual for those reporting data to NEARS
Reporting root cause information in NEARS has practical benefits.
Food safety personnel who use NEARS report information on root causes of foodborne outbreaks. NEARS helps programs understand outbreaks in their community and take action to stop them. CDC also uses this information to identify common root causes across outbreaks. This information can also help identify common practices and factors leading to outbreaks (also known as contributing factors) and can help determine best practices to address these issues.
For example, NEARS data showed that lack of managerial oversight was a common root cause of many outbreaks. In response, the Food and Drug Administration recommended that restaurants have a kitchen manager certified in food protection on site during hours of operation.
What are the main types of root causes?
There are five types of root causes.
- People: for example, managers not ensuring food workers are following safe food handling practices
- Equipment: for example, not having enough refrigerators to store perishable foods, leading to germ growth
- Economics: for example, lack of sick leave for food workers, leading them to come to work while sick and contaminate food
- Process: for example, not cooking a hamburger to the temperature needed to kill germs
- Food: for example, not treating food as a perishable item (such as not refrigerating something that needs to be kept cold)
What’s the difference between root causes and contributing factors?
In short, the contributing factor is the “how.” The root cause is the “why.”
For example, let’s say there’s a restaurant outbreak of Salmonella linked to raw chicken. The outbreak investigators determine that a new worker did not wash their hands after touching raw chicken. They then prepared a salad. In this outbreak scenario, the contributing factor would be cross-contamination. The root causes could be lack of training for food workers and high staff turnover.
By observing and asking questions, investigators can uncover these contributing factors and root causes.