That’s the number of cases being directly linked to a specific cause, it doesn’t mean that the actual number was 400/year. It’s like someone trying to estimate how much violence exists from watching the news. You’re likely to see major incidents, but you can only estimate the actual total.

I wouldn’t be surprised if it was well over 10k/year, but the CDC is conservative with their numbers for good reasons.

Also worth noting that there can be incidents where a massive number of people are infected in a short span.

> with the largest sickening over 2,000 water frolickers in one go.

Lots of people experience isolated events of food-borne illnesses for a variety of reasons. But when a restaurant gets 2000 people sick in a short time frame, we shut it down...and correctly so!

The average annual rate is not terribly informative for making effective public health decisions because it smooths out most of the interesting bits.