Select all modes of transmission that are likely to apply in this outbreak. For each mode of transmission selected, indicate whether it was a primary or secondary mode, and select the option that best describes the level of evidence available. For most outbreaks, there should only be one primary mode of transmission.

Primary mode – how the condition (disease) was contracted (see example below):

Secondary mode – how the contamination spread to others.

Example: Person eats Hepatitis A contaminated food and gets Hepatitis A. Other contacts of the case become unwell later. In this instance the primary mode would be contaminated food and the secondary mode would be person to person spread.

Level of Evidence Codes
1 - Elevated risk ratio or odds ratio with 95% confidence intervals not including 1 AND laboratory evidence
2a - Elevated relative risk or odds ratio with 95% confidence intervals not including 1
2b - Laboratory evidence, same organism and sub type detected in both cases and vehicle (to the highest level of identification)
3a - Compelling evidence, symptomatology attributable to specific organism e.g. scrombrotoxin, ciguatoxin etc
3b - Other association i.e. organism detected at source but not linked directly to the vehicle or indistinguishable DNA or PFGE profiles
3c - Raised but not statistically significant relative risk or odds ratio
4 - No evidence found but logical deduction given circumstances