Just read the following in a news site.
Does this mean we do not know the true extent of cases in UK.
Less than a third of people positive for Covid showing symptoms
Less than a third of people testing positive for coronavirus reported having symptoms, new figures have shown.
An analysis by the Office for National Statistics (ONS) found that only around 28% of people testing positive for Covid-19 reported any evidence of symptoms at the time of their swab test or at either the preceding or subsequent tests.
The remaining 72% of positive cases either did not report having any of the specific or general symptoms on the day of their positive swab test, preceding or subsequent swab tests or did not answer both questions, the ONS added.
It said that the findings, published on Tuesday, suggested that there was a “potentially large number” of asymptomatic cases of the virus.