Covid-19 tracker app shows one in 10 users has coronavirus symptoms

App, made by King's College London, is first of its kind and attracted 650,000 users within a day of launching

Premium

The first app monitoring the symptoms of people in Britain with suspected coronavirus shows that one in 10 users has a mild form of the virus at present.

Earlier in the week, King’s College London launched the Covid Symptom Tracker, saying it was "clinically urgent" to understand how many people are infected after the Government stopped testing in the community in the first week of March.

Within the first 24 hours, some 650,000 people had signed up, and an initial analysis revealed that 10 per cent of them were showing mild symptoms of the virus

Tim Spector, professor of genetic epidemiology a King's, said: "From the initial responses, so far around 10 percent of people are reporting symptoms associated with Covid-19, although many of these are mild.

"If after we analyse the results and separate out the unrelated from related symptoms, we could find that a large proportion of the population could have been affected, possibly millions. The larger the dataset, the better we can separate out the milder effects of the virus."

If the figures were representative of the whole country, and scientists are unsure if they are at the moment, it could mean that 10 per cent of the population currently has the virus – around 6.5 million people.

Researchers were quick to point out that it is too early to draw any concrete conclusions about what the initial figures mean.

Prof Spector usually works with a cohort of  15,000 twins to tease out the genetic factors behind disease. But when coronavirus put a halt to the work, he realised that the group could help scientists understand whether DNA was playing a role in who was getting coronavirus. 

He and his team developed an app so that they could track any symptoms of the virus while the twins were in lockdown, and realised it could also be rolled out to the whole of Britain.

"At the moment, there is no alternative system," he said. "I would have expected an NHS or Government version, but there isn't one. This could really help NHS planning, so you could see spots where there are lots of infections rather than just waiting for bombs to fall. 

"We will also be able to work out if some of the symptoms are real or not."

Prof Spector said he was amazed at the response and expected more than one million people to have registered by Thursday morning. People are asked to check in daily and report symptoms so the progression of the virus can be monitored.

"Our first analysis showed we're picking up roughly that one in 10 have the classical symptoms," he said. "So of the 650,000, we would expect to see 65,000 cases.

"Although you can have problems of self-selection and bias, when you’ve got big data like this you tend to trust it more. What we're seeing is a lot of mild symptoms, so I think having this data should help people relax a bit more and stop seeing it as an all or nothing Black Death situation.

"Other symptoms are cropping up. Thousands of people are coming forward to say they have loss of taste, and we may start to see clusters of symptoms."

As well as the population data, the app will help scientists drill down into what makes people more vulnerable to the disease as it inquires about underlying conditions such as diabetes and high blood pressure. It will also be rolled out in the US in the next 48 hours. 

“Most things, to some extent, are genetic as it's how our body responds to the virus and people have minor symptoms," Prof Spector added. "Some of the risk will be due to smoking, being overweight and other factors."

On Wednesday, Public Health England (PHE) promised that antibody tests which tell people if they have had the virus  and are now immune, will soon be available to the public, and King's is planning to update the app so people can input their results. 

At the daily coronavirus press conference on Wednesday, the government's chief science officer, Sir Patrick Vallance, said antibody tests would also be used to "understand the epidemic", suggesting that some community modelling will take place before they are rolled out to the public. 

The UK's chief medical officer, Chris Whitty, also said it was critical to find out how many people Britain were infected. A report from Oxford University this week suggested that as many as half of Britons may have already caught the virus. Reports from Wuhan, in China, have suggested that 80 per cent of cases could be mild or asymptomatic.

Professor Neil Ferguson told MPs on the science and technology select committee that he was working on assumptions that around five to 10 per cent of Londoners would end up being infected in the next six months – but the app shows the figures are likely to be higher.

Twins using the new app will be sent a home testing kit if they have symptoms to try and understand whether they relate to a coronavirus infection.

Although the Government has asked people to look out for a fever and cough, those infected have also reported night sweats, a loss of taste and smell, shivers and a feeling that the lungs are filling up with fluid.

The free app can be downloaded at the app store and has been developed with health data science company Zoe, a spin-off from King’s.