A top Government scientific adviser has denied that many cases of coroanvirus had been missed due to a failure to add the loss of taste and smell as a symptom of the virus.

England’s deputy chief medical officer Professor Jonathan Van-Tam told the Downing Street press briefing on Monday that very few Covid-19 patients experience loss of taste and smell as a lone symptom of the virus.

He said that it is often followed by a cough and fever, two of the key symptoms the Government has warned people to look out for.

His comments come after the loss of, or noticeable change to, taste and smell were added to the NHS’s list of coronavirus symptoms, weeks after experts first raised concerns that cases were being missed.

Experts said that an insistence that only fever and cough were the major symptoms had missed thousands of cases of the virus.

When asked whether the UK had missed diagnosis of coronavirus by failing to add loss of taste and smell to the list of symptoms, Prof Van-Tam said they were not always the first symptom.

He added: “What I can tell you is from the Public Health England data set, called the FF100 – the first few hundred cases – there are actually 229 cases in there, all laboratory-confirmed Covid, all of whom have been studied in considerable detail and 0.44% reported anosmia on its own as a symptom.

“So, the point about anosmia is it doesn’t always come as the first symptom.

“Even if it does, it is followed by the cough, the fever and many of the other symptoms I have talked about, referring to the WHO definition.

“So you don’t miss those cases.

“The important thing was to work out if this would add any sensitivity to the diagnostic cluster we were using and the answer is that it makes a small – a very small – difference and we have therefore decided to do it.”

Earlier, Health Secretary Matt Hancock announced that everyone aged five and over was now eligible to be tested for coronavirus if they are showing symptoms, including a loss of taste or smell.

Anyone suffering the newly-added symptoms, or a continuous cough or high fever, should self-isolate for seven days to stop the spread of infection, and anyone they live with should stay home for 14 days.

Until now, the NHS 111 coronavirus symptom checker has only listed high temperature and cough as the symptoms that require further action.

Prof Jonathan Van-Tam earlier told that reporters adding loss of smell and taste to the list 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.

Speaking about the findings on April 1, Prof Spector called for the rules to change, saying those with a loss of smell or taste needed to self-isolate.

On Monday, 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.”

Speaking after the change, Prof Spector said his team believe close to half of people who go on to test positive for Covid-19 never develop a fever or a cough.

“Public Health England finally adding anosmia (the loss of taste and smell) to its official list of symptoms is a step in the right direction but we feel more symptoms should be added,” he said.