True but some can be seen from an expected flu peak and then a drop off. It also isn't as simple as you imply. Personal experience from having to find some where for my mother. I visited a number of them. One common factor is age. It's pretty difficult to differentiate past that other than nursing homes but even those aren't dead simple.
Also it appears the NHS was prioritised over care homes.
https://www.msn.com/en-gb/news/coro...outbreak-minister/ar-BB14lzCI?ocid=spartanntp