A new app launched by scientists in the battle against coronavirus suggests 1.9 million people in the UK are infected.
It comes as the UK’s cases jumped to 38,168 and deaths rose to 3,605.
Contributors can track their daily health on the app, which is also being used by health professionals across the country, with early user data showing nearly two million have symptomatic Covid-19.
Researchers also found it shows wide disparities in the location of hotspots, which include cities such as London, Birmingham, Manchester, Liverpool, Glasgow and Belfast.
South Wales is also flagged by the data as badly affected, following a shortage in hospital beds.
As of April 1, 2020 there were 1,626,355 users of the tracker aged 20-69 who had recorded their symptoms, healthy or not.
Statistical models created by the researchers estimate that 79,405 of these users would be positive if tested (4.9%), but the data will become more accurate as the sample increases.
The figure was then extrapolated to the whole UK population, based on region, age and gender proportions, to form a total estimate.
Professor Tim Spector of King's College London, the lead researcher on the project, said: “Accurate real-time data is essential if we are to beat this disease.
“The more people we can get logging their symptoms on the app, the quicker we will be able to really understand this disease - it is clear levels of infection are very different around the country.
“We would like to thank every single person who is already participating, and would urge everyone else to download the app and check in every day, whether you are experiencing any symptoms or feeling fine.”
It comes amid a deepening rift between Number 10 and the NHS frontline over low levels of testing and basic supplies, and the lack of personal protective equipment (PPE) for doctors and nurses.
The Department of Health and Social Care has also asked manufacturers to fill in two forms if they can help with ventilators, testing kits and other essentials.