UK researchers have launched an app to help track the spread of Covid-19 and explore who is most at risk from the disease in an attempt to better understand the pandemic. The free Covid Symptom Tracker app asks users to fill in data including age, sex and postcode as well as questions on existing medical conditions, such as heart disease, asthma and diabetes and whether users take drugs such as immunosuppressants or ibuprofen or use wheelchairs. The app then asks participants to take one minute a day to report on whether they feel healthy and, if not, to answer questions on a wide range of symptoms, from coughs and fever to fatigue, diarrhoea and confusion. The team behind the app – a collaboration between researchers at King’s College London and Guy’s and St Thomas’ hospitals as well as the health data science company ZOE – hope it will provide real-time information on how the disease is spreading in the UK, including hotspots. “The concept is it is an early warning radar device because we are asking about non-classical symptoms as well, because many people are reporting non-persistent cough, or feeling unwell or a strange feeling of a lack of taste, or chest tightness that aren’t in the classical list but if we see it across the country in clusters we know they are probably real [symptoms of Covid-19],” said Tim Spector, a professor of genetic epidemiology at King’s College London, who is leading the work. “Speaking to clinicians in the hospital, especially in the elderly you get very different symptoms to the young so this idea there is only two types of symptoms – fever and long-term cough – is wrong. It can occur in many different ways,” he added. Spector said the app would shed light both on symptoms and the geographical spread of the disease. “The immediate thing is we will get known clusters of disease at different levels of severity all over the country and we will know what is going on,” he said. While the app is available to the general public, the team has also asked 5,000 twins and their families across the UK – who are already part of a wider research project – to use the app. Should these participants show signs of Covid-19, they will be sent a kit so that they can be tested for the disease. With the twins already having shared a large array of data with the team, from their genetic information to the makeup of their gut microbes, the researchers say they hope the work may help to shed light on why only some people become infected, and why some develop more severe symptoms than others. “What we will be able to do is, very fast, work out whether genes play a role or not, because we just compare the identical and the non-identical twins – we can do that in a few days,” said Spector. “The speed of what we are trying to do here is important – we put this whole project together in five days which would normally take about five months,” he added, noting there is no NHS equivalent. “If we got a million people reporting every day, that is an amazing tool for the epidemiologists.” In South Korea an app developed by the Ministry of the Interior and Safety allows those placed under quarantine to report their symptoms. The app also makes use of GPS tracking to alert both users and officials to see if quarantined individuals stray outside their permitted zone – a move apparently designed to help reduce super-spreading events.