I am unable to find any instances of random samples for Covid-19 tests being drawn from the general population (at the time of writing, see other answers for more recent developments). Current random test samples seem to have been drawn from populations most likely to be infected with the virus, such as healthcare professionals or those who have recently returned from communties most at risk, or those already presenting with influenza-like symptoms.
The ramping-up of tests in the UK that the question refers to relates to the overall testing capacity of the NHS. According to the NHS website:
Tests for coronavirus are only done if there's a high chance you could
have the illness.
This may be because:
- you have been in close contact with someone with confirmed coronavirus
- in the last 14 days you have travelled to a country or area with a high coronavirus risk – see our coronavirus advice for travellers
However, on 26th February, Public Health England announced that it would conduct random tests in a selection of GP practices and NHS hosptials on patients who are suffering from "severe respiratory infections but who do not display Covid-19 symptoms".
The Department of Health in Hawaii yesterday announced that they too would be conducted random tests for the virus, however these tests are also to be conducted on "Samples collected for influenza testing from patients with respiratory symptoms", and not on samples collected from the general population.
In the Netherlands, random tests were conducted on hospital staff in Brabant, resulting in 4% being identified as having contracted the virus. Again, though, I cannot find any evidence on tests having been conducted on a general sample of the population as a whole.
In New York, in a briefing delivered on Monday, Governor Andrew M. Cuomo gave an insight into the current testing protocol:
The testing - we'll go through the latest numbers, but let's also
remember the context for testing if we can: The more you test, the
more positives you will find, and you are testing primarily a suspect
group because we're testing people who we believe came in contact with
a positive person. We want that data because we want to find out who's
positive so we can isolate them and reduce the spread. But it is not a
random sample, it is not statistically representative of anything.
It's testing a particular universe that we believe may very well have
been exposed to a positive person. So it's not statistically, I don't
know what it means, I take it as good news because I want to be
finding the positives so we can isolate them and we can reduce the
spread. And that's what the testing is all about.
It seems, therefore, that given the rapid spread of the disease and ongoing battle for
health services to simultaneously cope with the current situation whilst also preparing for the future spread of the virus, testing capabilities are being prioritised for patients most at risk of having contracted the illness, in order to provide treatment and quarantine those who test positive. While statistical analysis of a random sample of the population might be interesting, it is not particularly helpful for health services, most of which acknowledge that community spread is inevitable.