King's College London

The latest analysis of data from the COVID Symptom Tracker app, used by over 2 million people, shows the rate of new symptoms being reported nationally has slowed down significantly in the past few days. The latest figures estimate that 1.4 million people in the UK aged 20-69 have symptomatic COVID-19, a fall from 1.9 million on the 1 April. 

Researchers behind the app say that these figures suggest that staying home is having a big impact on the spread of the virus in the UK. They say the drop in new symptoms indicates that although the number of hospital admissions and deaths from COVID-19 are currently rising, they should start to fall in about two weeks provided social distancing continues. They believe the two week lag is caused by the delay between symptoms starting and becoming very severe.  

This data concurs with what has been reported by NHS digital based on much smaller numbers. They show a decline in the number of calls to NHS 111 with COVID-19 since the 22 March¹ .

While symptoms have been decreasing nationally, researchers say that their data shows that in all areas there are still many people with active symptoms. It supports both the success of lockdown and the importance of maintaining it. The data also shows that individual areas vary. Most of the country’s larger cities like London, Birmingham, Glasgow, and Liverpool continue to have very high levels of symptoms in the community, even this far into lockdown. Other hotspots include South Wales. There are significantly higher levels of symptoms across the Midlands, the North of England and Southern Scotland than in the South West of England. 

Developed by researchers at King’s College London and healthcare science company, ZOE, the COVID Symptom Tracker has been used to log symptoms by over 2 million people across the UK, with over 10 million individual reports so far. Members of the public are using the app to track their daily health whether they are healthy or showing potential COVID-19 symptoms. It is also being used by healthcare and hospital workers nationwide so their increased risk can be recorded.

The researchers have developed a statistical model which analyses millions of COVID Symptom Tracker data points, including thousands of people who have had tests for COVID-19, in order to predict which combination of symptoms indicate someone is likely to test positive. This model is then applied to the UK population aged 20-69 and to regions of the country accounting for age and gender differences to provide maps over time. The most predictive individual symptoms, in order of importance were: lack of taste & smell, fatigue, shortness of breath, fever and persistent cough. The model estimates that 3.5% of these app users would be positive if tested.

Lead researcher Professor Tim Spector from King’s College London, said: 'It is really encouraging to see that the rate of new symptoms being reported is beginning to fall. Even though hospital admissions and deaths are still on the rise, we hope that these figures offer a much needed light at the end of the tunnel.'

An interactive map allowing anyone to see the distribution of COVID-19 in their area is available at covid.joinzoe.com.

The app is available to download from the Apple App Store and Google Play from the links at covid.joinzoe.com.

NHS 111 call data captured on 7th April 2020 from the following sources:

• https://digital.nhs.uk/data-and-information/publications/statistical/mi-potential-covid-19-symptoms-reported-through-nhs-pathways-and-111-online/latest 
• https://app.powerbi.com/view?r=eyJrIjoiNzhiNTlhZmUtYmI1Zi00NWU1LTgzNWUtNGViZTExNzlhMGFkIiwidCI6IjUwZjYwNzFmLWJiZmUtNDAxYS04ODAzLTY3Mzc0OGU2MjllMiIsImMiOjh9