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Research update: April 1, 2020
The first results from our COVID-19 symptom tracking app show that losing your sense of smell or taste is a stronger predictor of coronavirus infection than fever.
According to the NHS, the most common symptoms of coronavirus infection are fever (high temperature) and a new continuous cough.
However, many people are also reporting symptoms such as aches and pains, chills, tiredness, headaches and diarrhoea. But there have also been plenty of anecdotal reports of patients suddenly losing their sense of smell or taste, particularly in the early stages of infection.
Is loss of smell or taste a symptom of COVID-19?
To find out more about the early warning signs of COVID-19, our researchers at King’s College London and ZOE have been analysing data from by nearly 2 million 400,000 ‘stay-at-home scientists’ who have been submitting daily health updates through the COVID-19 symptom tracking app.
We found that of 400,000 people reporting one or more symptoms between 24-29th March::
- 53% had fatigue or tiredness
- 29% had a persistent cough
- 28% suffered from shortness of breath
- 18% had lost their sense of smell (anosmia) or taste
- 10.5% were suffering from fever
Of these 400,000 people, 1,702 had been given a test for COVID-19. 579 had tested positive, while 1,123 were negative.
Doing a quick bit of maths tells us that of the people who were definitely infected by coronavirus (i.e. tested positive), nearly six in ten (59%) reported losing their sense of smell or taste compared with only around two in ten (18%) who tested negative.
This map shows the hotspots in the UK where app users are reporting loss of smell or taste:
Our team then crunched all the symptom data together to build a computer programme (model) combining data on loss of smell and taste, fever, persistent cough, fatigue, diarrhoea, abdominal pain and loss of appetite to predict whether someone is likely to be suffering from COVID-19 or not, even if they haven’t been tested for the virus.
When we used the model to look across the 400,000 people who had reported symptoms but not yet had a COVID-19 test, we found that more than one in ten (13%) are likely to be infected by the virus based on their combination of symptoms.
That adds up to an extra 50,000 individuals who are likely to have as yet unconfirmed COVID-19 infections.
Why does COVID-19 cause loss of smell and taste?
Our senses of smell and taste are closely intertwined. Most of what you taste when you eat and drink actually comes from its smell, rather than its effects on the tastebuds on your tongue.It’s not entirely clear why coronavirus infection leads to a loss of smell and taste.
The key probably lies in the olfactory epithelium: a layer of neurons (nerves) and other supporting cells at the back of the nose that detect smelly chemicals in the air and relay this information into the brain.
One idea is that the virus causes inflammation and swelling in the back of the nose, interfering with normal smelly sensations. Scientists at Harvard have also just published a pre-print (non-peer-reviewed results) suggesting that the coronavirus responsible for COVID-19, known as SARS-CoV-2, may infect the supporting cells in the olfactory epithelium that surround the neurons responsible for detecting scents.
What should I do if I lose my sense of smell or taste?
Loss of smell or taste is one of many symptoms of COVID-19, and people respond in different ways to infection (something we’re working hard to understand from the data we’re collecting).
It’s important to remember that the common cold and other respiratory infections can also make you lose your sense of smell. Conversely, you may be infected with coronavirus without suffering any loss of smell or taste at all. And while loss of smell does seem to be a genuine early-warning sign of COVID-19, fever and coughing are still the most important symptoms to look out for.
Our lead researcher Professor Tim Spector says, “When combined with other symptoms, people with loss of smell and taste appear to be three times more likely to have contracted COVID-19 according to our data, and should therefore self-isolate for seven days to reduce the spread of the disease.”
Given the circumstances, the best advice for anyone noticing loss of smell or taste is to treat yourself as being infectious. That means following the Government guidelines and starting self-isolation to protect your family, the NHS and the wider community by stopping the spread.
Other updates
News: the latest COVID estimates
Symptomatic COVID cases continue to fall across the UK even as our contributor base grows to over 2.3 million. Discover our latest estimates across England, Scotland and Wales.
Symptomatic COVID cases fall by 71% over 2 weeks
The number of cases of predicted symptomatic COVID has fallen from 2 million to 582,640 in just over two weeks (01 April to 15 April) according to the latest data from the new COVID Symptom Tracker app.
How long will COVID lockdown last?
Professor Tim Spector and ZOE, CEO Jonathan Wolf share projections on cases of COVID-19 to discuss when the pandemic will end and the risk of ending lockdown too early.
First Minister Mark Drakeford makes urgent appeal
First Minister Mark Drakeford and NHS Wales are appealing to the Welsh public to download the COVID Symptom Tracker app to help the NHS response to COVID-19 in Wales.
You asked: Can food help immunity?
Many COVID Symptom Tracker participants have been asking our scientists whether there are certain foods that they should be eating to help combat COVID-19 or fend off coronavirus infection. We reveal the truth backed by science.
The impact of self-isolation
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.
Webinar: Predicting symptomatic COVID-19
ZOE and King’s College data science and machine learning teams have been working around the clock to create a machine learning model that uses Symptom Tracker data to predict COVID-19 in the UK. Here’s how they’ve done it.
COVID App updates: March
After receiving thousands of data-points from you on app improvements we are happy to say that we have updated the app experience for you. Here is an overview of new features we’ve made.
How do I delete my data?
You have the right to remove your data from our service at any time. We’ll tell you how it is protected and how you can remove it at any time.
Mapping your symptoms
Our data science team has analysed some of the most commonly reported symptoms in the UK. We’ll show you what they are and where they’re being experienced by those using our COVID Symptom Tracker.
How is your data secured?
Your data is protected under “General Data Protection Regulation” (GDPR) which extends beyond the standard requirements of US data protection regulations. Read more about how your data is protected and the security partners making it possible.
Webinar: Symptom Analysis
Watch our March 30th research update webinar. Doctors and clinical researchers Claire Steves and Tim Spector share an update on the insights they’re learning from the COVID Symptom Tracker and how we’re using it to aid the global health community.
Smoking and COVID-19
We know that smoking isn’t a healthy habit, but have you wondered if it might increase your risk of COVID-19? Dr. Claire Steves and the research team from King’s College London tell us more in our latest update.
How your data will help fight COVID-19 in the US
As the COVID-19 coronavirus pandemic grips the United States, we are recruiting millions of citizen scientists across the nation. Our aim is to slow the outbreak of the disease and identify those at risk sooner. Here’s how you can help out from home.
Who are the 1.5 million citizen scientists?
The COVID symptom tracker has now been downloaded over 1.5 million times. As the number of contributors continues to grow we take a look at who they are.
Could non-classic symptoms indicate mild COVID?
Scientists and researchers from Kings College London report the state of the nation’s reported symptoms as of 3pm on 27th March 2020.
King’s College London: The team analysing your data
We talk to Dr. Claire Steves, Senior Clinical Lecturer at King’s College London who is leading the research team analysing your data.
Over 1 million citizen scientists and counting!
The COVID symptom tracker was downloaded over 1 million times in just 36 hours.
How your data will provide clues to tackle COVID-19
Research lead Dr. Tim Spector, professor of genetic epidemiology at King’s College London and director of TwinsUK, discusses how your data will be used.
