micmc47 I think the corona virus came here to the UK, and probably other countries, long before it was announced as such.
For example, in January, thousands of Chinese students returned to University from China after going home for Chinese New Year. I know of cases of people working with them who had very a bad flu-like illness with severe coughing for up to 3 weeks in late January. Others I know had the "coughing flu" for a few days in January or February. Nobody knew what it was and most did not go to the Doctor. Most now believe they had COVID19 as their symptoms match the list.
We cannot tell when this silent virus came to each country from China or even elsewhere. We know people can be infected and not feel particularly ill, carrying on with their daily life as usual. We only know the first diagnosed cases after it had been recognised. There would have been many cases which might have been symptom free or so mild it was unremarkable and others like the people I know who had "something" which in hindsight they see had the same symptoms, but at the time they did not know about covid19's symptoms and dangers.
As for saying a lot of science goes behind the PM's announcements! The trouble has been, particularly at the start, our PM ignored advice from very eminent leaders in the fields of virology and epidemiology and did not follow their advice, thus not containing the virus' spread. Think of the questions about why we were not doing what Ireland or France were doing? Think of the terrible fudging explanation about flattening the curve. This could only be done by stopping social contact not by letting people mix! Now he's had to say that the numbers of those ill and needing help has risen more quickly and much higher than "they" anticipated! So no flattening of the curve then, but a sudden steep rise! Which he was told would happen due to his measures! It is far too late to close this stable door now. Thousands upon thousands will die needlessly and before their time simply because our PM and his government did not listen to the experts.
It's time Johnson stood down and an inter-party committee with experts in virology and epidemiology and psychology was formed to lead us through this crisis. Daily bulletins need to be made by an intelligent, informed and comprehendible person. Not by a bumbling stammering bluffing idiot who only wants the lime light and changes his plans so many times we get dizzy and leaves people more confused after he has spoken than before.
But my point remains micmc47, nobody knows when this virus arrived in the UK and nobody knows the number of people who had it before it was properly recognised as this virus.
Maybe, if the government wanted to understand it better, they could ask people to send in their data as to whether they were ill prior to the beginning of March, say. They could ask, symptoms, dates, duration, whether a medic was consulted, did the person go out, did they mix, etc...