A loss of taste or smell have been added to the NHS coronavirus symptoms list, weeks after experts first raised concerns that Covid-19 cases are being missed.
Anyone suffering loss of taste or smell, or a noticeable change, should now self-isolate for seven days to reduce the risk of spreading the infection, according to guidance from the UK's chief medical officers.
If the symptomatic person lives with others, they should stay at home for seven days, while all other household members should stay home for 14 days even if they do not have symptoms.
The move means loss of smell or taste will now be listed alongside fever and cough as the main symptoms of Covid-19.
Until now, the NHS 111 coronavirus symptom checker has only listed high temperature and cough as the symptoms that require further action.
England's deputy chief medical officer, Professor Jonathan Van-Tam, told reporters the move would mean 94% of cases where people have symptoms are now picked up, a rise from 91% previously.
It comes after a study led by Professor Tim Spector at King's College London found that 59% of Covid-19 positive patients reported loss of smell and taste, compared with only 18% of those who tested negative for the disease.
These results were much stronger in predicting if somebody had coronavirus than if they reported fever.
Speaking about the findings on April 1, Prof Spector called for the rules to change, saying: "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."
On Monday morning, he heavily criticised the Government's stance so far, saying infected people had been encouraged back to work due to a failure to track symptoms properly.
He said 50,000 to 70,000 people in the UK with Covid-19 were currently not being told to self-isolate even though they had the virus.
He blamed Public Health England (PHE) and the wider strategy, saying an insistence that only fever and cough were the major symptoms had missed thousands of cases.
He added that there are even more symptoms – such as tiredness, stomach pain or diarrhoea – that could be included as possible coronavirus symptoms.
He said: "We list about 14 symptoms which we know are related to having a positive swab test.
"These are not being picked up by the NHS. This country is missing them all and not only underestimating cases, but also putting people at risk and continuing the epidemic.
"There's no point telling people to be alert if they don't know the symptoms."
ENT UK, the professional membership body representing ear, nose and throat surgery in the UK, said it had first warned that loss of smell and taste were symptoms of coronavirus eight weeks ago, saying it had shared those details with PHE.
The World Health Organisation (WHO) listed loss of smell and taste as "less common symptoms" several weeks ago and other countries, including the US, added the symptom.
Despite these warnings, Prof Van-Tam said on April 3 that the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag) had looked at the issue and concluded loss of smell or taste should not be added to the UK's symptom list.
But on Monday, that guidance was changed, with Prof Van-Tam saying advisers had needed to look at the issue in detail.
He said scientists had had to "work out very carefully" how valid loss of taste or smell were in counting cases and where in the course of an illness the symptoms might occur.
Prof Spector's paper cited loss of smell and taste as being more frequent in people who test positive "but very much in the presence of other symptoms", he added.
"The question for Nervtag has always been: At what point can we be sure that by adding anosmia (loss of smell) or adding anything else, frankly – there's plenty of other things such as fatigue, diarrhoea loss of appetite – at what point would adding any of these definitely improve and help us to pick up cases?
"That work has now been completed. And that's why we've got to the position we have now, not just about whether or not anosmia exists – it's about what role it plays in identifying cases, and that's taken time to work through those data."
It comes as:
– A decision on whether schools will return next month is likely to be made this week, Downing Street hinted. The PM's spokesman said: "You can see from the discussions that have been taking place that we have been seeking to resolve this as soon as we can."
– Coronavirus outbreaks have been reported in almost four in 10 care homes in England, according to Number 10.
– Plans to impose a 14-day quarantine on international travellers arriving in the UK will be reviewed every three weeks, Downing Street said.
Prof Van Tam acknowledged there were other symptoms of Covid-19, such as fatigue, stomach and muscle pains, but these were too common generally.
Prof Nirmal Kumar from ENT UK, told the BBC the change to including loss of smell or taste was "better late than never".
Speaking at a press conference in Downing Street last month, Health Secretary Matt Hancock said his own loss of taste had not been permanent.
"For me personally, I did lose my sense of taste but it has come back though," he said.