@FlamingoAndJohn There are 100 clinics and some hospitals testing people for Coronavirus if they present with certain symptoms as part of a pilot. I believe the point of this is to try and work out how much community transmission is going on. This is part of the reason that such high numbers are being tested in the UK compared to some other countries. I believe the plan is to extend this program if it's deemed necessary.
Due to the fact that there are 2 people in the UK where we can't trace the transmission, we can assume there are/have been some cases in the community that have not been caught. However, due to the fact there are only those 2 cases (so far), I think it's fair to assume the spread in the community is not that widespread, because we would have caught more than 2 cases- in another scenario, the pilot could have turned up 100 cases straight away, and that would be a totally different scenario.
If you compare this to e.g. the Dutch situation, where they have 18 cases from only doing about 200 tests, and they have cases of community transmission already- then I think we do have a better picture of how many cases there are in the UK.
We're also not in the same situation as the US where cases of community transmission are turning up all over a large country and we can safely assume some people aren't getting tested due to their lack of insurance cover.
I'm not saying we have the situation under control in the UK at all- but I don't think there are loads of undetected cases in people who haven't traveled/been in close contact with someone who has traveled, yet.
This week we will start to see how many people brought it back from Italy with them, and then next week we may start to see who they have passed it on to, and that will give us a picture of what we are dealing with.
If there's a sudden spike in community transmission cases, then of course this all changes.