Throughout the coronavirus pandemic, the main symptoms of the virus that members of the public have been told by the NHS to look out for have been a high fever, a new, persistent cough and a loss or changed sense of smell and taste.
In addition to the main symptoms, people around the world have reported experiencing various other side effects that they believe could be linked to the virus, including “Covid toe” and rashes on other parts of their bodies.
In September, a study conducted by The University of Belfast found that diarrhoea and vomiting could be symptoms for coronavirus.
Meanwhile, in July it was reported that researchers are calling for skin rashes to be added to the NHS’ official list of symptoms after a study found that one in 11 patients who tested positive for Covid-19 developed a rash.
The study, which was carried out by King’s College London, was conducted using data from 20,000 Britons who either tested positive or were suspected to have had the virus.
Epidemiologists, ophthalmologists and dermatologists have warned about other symptoms that could be indicative of a patient who is positive of the coronavirus.
Here are several lesser-known symptoms that are currently being investigated for possible links to Covid-19.
In January, researcher Tim Spector, who is the principal investigator of the Zoe Covid symptom app at King’s College, where over 4.5m people have helped record data on potential symptoms, tweeted about a possible new symptom.
Spector and his colleagues were among the first to highlight that change in sense of taste or smell should be recognised officially, months before it was added to the NHS list.
He said: “One in five people with Covid still present with less common symptoms that don’t get on the official PHE list - such as skin rashes. Seeing increasing numbers of Covid tongues and strange mouth ulcers."
And he also warned people: “If you have a strange symptom or even just headache and fatigue stay at home!”
Although this has not been officially recognised by PHE or the NHS, the Zoe study is the largest community monitoring in the world.
Headaches appear on the World Health Organization’s list of less common Covid symptoms. A study of nearly 400 Covid patients published in January 2021 found that 13 per cent developed a headache.
Researchers at the Hospital Universitario de La Princes in Madrid, Spain, found that headaches were more likely to be associated with milder cases of the virus.
A study of 139 patients conducted at ClermontâFerrand University Hospital in France found that 59 per cent experienced headaches during the acute phase of the illness and 3.6 per cent were still experiencing them one month later.
The NHS doesn’t currently list headaches as a symptom of Covid, and doesn’t suggest getting a test if you are suffering only from a headache.
The team of researchers conducted an investigation on a small number of Covid-19-positive patients.
In more than 60 per cent of the cases of intensive care patients, they discovered evidence of confusion and agitation.
The scientists, from the UK and Italy, concluded that patients who have to stay in intensive care for long periods of time and who are in need of ventilation treatment may be at greater risk of experiencing delirium and confusion.
The research, which assessed patients with Sars (severe acute respiratory syndrome), Mers (Middle-East respiratory syndrome) and Covid-19, also found that people who exhibit mild symptoms are less likely to experience as significant an impact on their mental health.
Professor Gitte Moos Knudsen, chair of the Department of Neurology and Neurobiology Research Unit at Copenhagen University Hospital, explained that “any condition associated with hospitalisation, fever, depletion of sensory inputs – particularly in the elderly – carries an increased risk for delirium”.
“In Covid-19 patients that have been artificially ventilated, a PTSD condition may arise; but we do not have evidence that the frequency is higher in Covid-19 patients than in any other disorder,” Professor Knudsen added.
Dr Michael Bloomfield, consultant psychiatrist and head of Translational Psychiatry Research Group University College London, said that the study is “important and well-conducted research”.
“This study provides further evidence that the harm caused by Covid-19 extends beyond the widely reported effects on the lungs. This study tells us that Covid can have profound effects on mental health,” he stated.
“Of particular cause for alarm is the finding that a third of patients from previous epidemics experienced post-traumatic stress disorder and it seems reasonable to anticipate similar rates of PTSD in people who have had life-threatening Covid.”
Tom Dening, professor of Dementia Research at the University of Nottingham, pointed out that scientists “know much less about the prevalence of mild or asymptomatic Covid-19”, adding that patients who experience milder cases of the virus are less likely to experience mental health issues, “especially delirium, which is generally a marker for severe physical illness”.
“The authors draw attention to how delirium is an important and common feature in people admitted to hospital with coronaviruses. In some situations, probably more so in older people, delirium may even be the presenting feature of a severe Covid-19 infection, so it’s important that health professionals and care home staff are aware of this possibility,” the professor said.
Covid toe and other rashes
On Wednesday 15 July, it was reported that researchers are calling for the NHS to officially recognise skin rashes as a symptom of the coronavirus.
The study conducted by King’s College London assessed 20,000 Britons who either tested positive or were thought to have had Covid-19 and data from the Covid Symptom Study app, which contained information relating to 336,837 users who self-reported their symptoms.
More than 2,000 of the app’s users tested positive for the coronavirus, with 8.8 per cent reporting blotchy and itchy skin.
Furthermore, 8.2 per cent of the 17,000 people strongly suspected to have had the virus reported developing a rash.
The study has not yet been peer-reviewed. Dr Mario Falchi, who led the study, is urging for rashes to be formally recognised as symptoms of the virus in light of his findings.
In a statement sent to The Independent, Dr Tanya Bleiker, president of the British Association of Dermatologists, explained that in the early stages of the pandemic, “the various skin manifestations of the disease were poorly understood and not common knowledge”.
“However, a series of important studies has done fantastic work in this regard, this study being the latest of these,” Dr Bleiker stated. “It will play an important role in building our understanding of the disease as a whole”.
Dr Bleiker said the British Association of Dermatologists is “delighted” to be working with the team at King’s College London “to develop a dedicated website which will host a library of the different skin manifestations of Covid-19”.
“We hope that this will be of benefit to healthcare professionals as well as the public who may be unaware of skin symptoms which would warrant self-isolation,” the organisation’s president said.
In May, the term “Covid toe” was increasingly discussed as a possible symptom of the coronavirus.
The condition, which involves chilblain-like lesions appearing on the feet, is one of several skin conditions currently being investigated as potential signs of Covid-19.
On 29 April, researchers from Spain published a study concerning the “cutaneous manifestations of Covid-19 disease”, cutaneous meaning “relating to the skin”.
The scientists came across five different forms of rashes affecting 375 Covid-19 patients.
These included itchy or painful chilblain-like lesions on the hands and feet, including Covid toe; small blisters on the torso; small, flat and raised red bumps; blotchy red or blue-looking skin; and pink or white raised areas of the skin that looked similar to nettle rash.
Dr John Ingram, editor-in-chief of the British Journal of Dermatology, commented at the time that the investigation was “the most definitive piece of research on the skin features associated with Covid-19 to date”.
So-called "Covid toe" is emerging as yet another possible sign of the new coronavirus, even though U.S. officials have not yet listed it among the symptoms. Some experts say it may reflect a healthy immune response to the virus. https://t.co/rytrWnf1L3
— The New York Times (@nytimes) May 1, 2020
“There has been speculation for some time that the virus is responsible for a number of skin signs, but until now these had largely been individual or small scale case reports. This study represents a much more systematic and thorough categorisation of the features,” he stated.
“The main beneficiaries of this research will be medical professionals and researchers. It will be useful in diagnosing people with Covid-19, particularly those with relatively few symptoms. It will also provide a firm foundation for future research into COVID-19 and the skin.”
The American Academy of Dermatology has created a dedicated task force to study Covid toe.
Several reports have been circulating as of late regarding the possibility that the coronavirus could cause conjunctivitis, an eye condition that develops as a result of infection or allergies.
In April, the American Academy of Ophthalmology released an alert for ophthalmologists highlighting two studies that indicated the potential link between the virus and conjunctivitis.
In a study of 30 patients hospitalised for the virus in China, one had conjunctivitis. “That patient – and not the other 29 – had SARS-CoV-2 in their ocular secretions. This suggests that SARS-CoV-2 can infect the conjunctiva and cause conjunctivitis, and virus particles are present in ocular secretions,” the American Academy of Ophthalmology said.
In a larger study published in the New England Journal of Medicine, which assessed 1,099 hospitalised coronavirus-positive patients in China, nine had “conjunctival congestion”.
In a statement sent to The Independent, Moorfields Eye Hospital in London emphasised that “of the many people infected worldwide with Covid-19, there are only a few reports of patients presenting with conjunctivitis.” The hospital added that there is “therefore a possibility, but it is incredibly rare”.
The hospital has not noticed an increase in patients being admitted for conjunctivitis during the pandemic, adding that the “there is no evidence that the conjunctivitis in Covid-19 is more severe than any other type of viral conjunctivitis”.
Moorfields outlined that if the virus were to cause a patient to develop conjunctivitis, this would likely occur either through “direct exposure of the surface of the eye to Covid-19” (such as by rubbing the eyes) or “indirect exposure where the virus tracks up the duct that connects the surface of the eye to the nose and throat”.
The Royal College of Ophthalmologists (RCO) and the College of Optometrists explained that if a person presents conjunctivitis after contracting coronavirus, it is unlikely they would do so without also showing other, more recognisable symptoms of the virus.
“Recent reports have suggested that Covid-19 may cause conjunctivitis, and it is known that viral particles can be found in tears, which has caused some concern amongst eye health professionals,” the organisations stated.
“It is recognised that any upper respiratory tract infection may result in viral conjunctivitis as a secondary complication, and this is also the case with Covid-19.”
The RCO and the College of Optometrists stated that as viral conjunctivitis is not listed as an official symptom of Covid-19, medical practitioners should treat patients with the condition “as they would usually treat any presentation of viral conjunctivitis”, as long as they are not also showing signs of the coronavirus.
They stressed that during the pandemic, “scrupulous infection control and hand hygiene measures” should be carried out when treating all patients, while any “close examinations” should be “kept to a minimum safe level”.
Loss of smell and taste
The announcement came following the government’s previous declaration that loss of smell and taste would “absolutely not” be added to the list of symptoms members of the public should be aware of.
For weeks, experts have warned that countless cases of Covid-19 could be being missed due to the lack of guidance being given to people experiencing anosmia, many of whom will have been encouraged to return to work.
The NHS is now encouraging anyone who experiences loss of smell and taste, or a noticeable change, to self-isolate for seven days, while other members of their households are advised to stay at home for 14 days, even if they don’t show symptoms.
Natalie Brookes, a consultant ENT surgeon and rhinologist and medical director at The Harley Street ENT Clinic, told The Independent that prior to the guidance change, her clinic was in contact with its advisory body ENT UK, who stated that “they think anosmia could be related to Covid”.
“If I developed a sudden loss of sense of smell, with or without a mild upper respiratory type symptoms, I would definitely self-isolate at the moment,” Ms Brooks added.
Professor Carl Philpott, director of medical affairs and research at charity Fifth Sense, explained to The Independent that as common colds and viruses often cause initial congestion of the nose, this can lead to “post-viral smell loss”.
“If you look at the tissue in detail under the microscope you see that the fine hair-like endings of the receptor cells have fallen off and therefore the cells are no longer able to pick up odour molecules from the nose,” Professor Philpott says.
He adds that Covid-19 “appears to have a high concentration in the nose”, and states that as the majority of anecdotal reports are showing people experiencing transient smell loss that lasts for around seven to 14 days, “it’s probably more likely that the virus is causing some sort of inflammation in the olfactory nerves, rather than it causing any damage to the structure of the receptors”.
Inflammation among children
In May, it was reported that up to 100 children in the UK had been affected by a rare disease linked to the coronavirus.
The syndrome appears to bear similarities with Kawasaki disease, causing an inflammatory response in children ranging from infants to older teenagers.
Russell Viner, president of the Royal College of Paediatrics and Child Health (RCPCH), stated that while symptoms are fairly mild for the majority of children affected, “a small proportion have become much more severely ill”.
Professor Rosalind Smyth, director and professor of Child Health at the UCL Great Ormond St Institute of Child Health added that “it remains the case that the great majority of children with COVID-19 have mild symptoms only”.
In a report on the cases admitted to London Children’s Hospital, it said that symptoms include “unrelenting fever”, “variable rash”, conjunctivitis, swelling, pain and “significant gastrointestinal symptoms”, such as diarrhoea and vomiting.
NHS England released an alert about the condition in late April, stating that the cases of children in intensive care with a “multi-system inflammatory state” have “overlapping features” of two health conditions – toxic shock syndrome and “atypical” (or incomplete) Kawasaki disease.
The health service added that the children have also had “blood parameters consistent with severe Covid-19 in children”.
Dr Julia Kenny, consultant in paediatric infectious diseases and immunology at Evelina London Children’s Hospital explained that much more research is needed on the subject before it can be more thoroughly understood.
“As this new syndrome has only been identified in the past four weeks, it will be vital to learn more about its presentation and treatment, and to establish how the disease mechanism is linked to Covid-19 which has pre-dominantly affected adult patients to date,” Dr Kenny said.
Professor Smyth added that at the moment, “it seems that this condition is very rare”.
“One of the purposes of the current alerts and guidance is to increase awareness, so that all possible cases can be identified. This will help to identify the true incidence,” the professor outlined. “We know very little about the cause and mechanisms. Indeed, our understanding of the mechanisms of the condition which it may resemble, Kawasaki’s syndrome, is incomplete.
“Working out a possible relationship to Covid-19 will depend on testing for the virus, repeatedly during the course of the illness, and for the antibody, following recovery, to work out if there is a temporal relationship with SARS-CoV-2, in some, or all, cases.”
Diarrhoea and vomiting
In September, a study conducted by The University of Belfast found that out of 1,000 children around the age of 10, 97 per cent who had tested positive for Covid-19 also had gut-based symptoms such as diarrhoea and vomiting.
While neither of these symptoms appear on the NHS's list of official symptoms for coronavirus, both appear on the US Centers for Disease Control's list of possible symptoms.
Lead researcher Dr Tom Waterfield told the BBC: "We know that, thankfully, most children who get the virus will not be very ill with it - but we still do not know how much children may be spreading it.
"We are finding that diarrhoea and vomiting is a symptom reported by some children and I think adding it to the list of known symptoms is worth considering."