Declaring the outbreak over

Investigative partners agreed to declare the outbreak over on September 2, 2014. The calculation for this date is summarized in the following figure:

Declaring the outbreak over

Note that this date is not static; the date should be re-evaluated if new, relevant information comes in (e.g., case reporting increases above baseline levels in the “lag window”, the CFIA reports that they have found some product on store shelves despite effectiveness checks, or new traceback information suggests other products/product lots may be contaminated).

Question 4-1: How would the date the outbreak can be declared over change if there are multiple new cases reported whose dates of onset occurred after the product was recalled?

ANSWER
  • Multiple cases reported after a product was recalled would suggest that either the recall was not well communicated, or that other products/product lots may be contaminated.
  • In this situation, the most recent date of illness onset should be used to re-calculate the date the outbreak can be declared over.
  • For example, if the most recent case’s date of illness onset is August 26, then the outbreak would be declared over August 26, 2014 + 10 days + 20 days = September 25, 2014.

 

Question 4-2: How would the date the outbreak can be declared over change if there was a new case reported after the outbreak had already been declared over? 

ANSWER

Having one case reported after the outbreak has been declared over will not necessarily change the date the outbreak is declared over. However, this case should still be included in the scope of the outbreak and investigated.

If it is confirmed that the case consumed a recalled product, this new case does not represent an on-going issue and would not affect the date the outbreak is declared over.

However, if there appears to be an on-going risk, the date could be revised based on any new information. Investigative partners may consider re-opening the investigation.

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