In the 2012 pet food outbreak, the majority of dogs and cats owned by case patients were mostly healthy.

• A. Mostly sick
• B. Mostly healthy
• C. None sick
• D. Unknown

Answer: (B)

In outbreak investigations, exposure to a contaminated product does not automatically cause illness in every exposed animal; the proportion that becomes ill is the attack rate. For the 2012 pet food outbreak, the data showing that the majority of dogs and cats owned by case patients were mostly healthy indicates a relatively low attack rate among exposed pets. This reflects that many animals exposed to the contaminated product did not develop disease, which can happen due to factors like dose, timing, individual susceptibility, or immune status. Saying most were sick would imply a higher attack rate than was observed, while none sick would imply no illness at all, and unknown would suggest insufficient data.