Looking at the ratio is meant to control for the very different flu seasons we experience. What this is showing is that every year prior to this we had a very constant ratio of older patients to total patients week by week. However, this year that ratio has been shooting up. There's a few other explanations for why this is, but it seems likely to me that this represents an illness that is disproportionately impacting older people. We know that coronavirus does this. We also know that it has led to very few hospitalizations (relatively speaking) of 25 and under.

Now, for coronavirus to start to overwhelm these numbers in this way, it means you probably would have to have a lot of cases. You could probably use this and other numbers to try and estimate coronavirus cases, but you wouldn't have an exact number. There's some reason for optimism in that if this is wider spread than previously thought, it means the fatality rate is lower, and we're closer to herd immunity. But there's also room for pessimism in that it will mean the task of controlling this will be far harder (millions have it, many without even realizing it).

I mostly share because I think it's an interesting quirk in the data that I haven't seen talked about anywhere else.