You should be aware of four lesser-known coronavirus symptoms as infections continue to increase.
A high temperature, a persistent cough and a loss of taste or smell as official signs of Covid-19.
However some people experience milder symptoms, which in some cases are the only indications they have been infected.
As the world continues to battle the coronavirus, here are some of the unofficial signs of coronavirus:
Stomach ache
Some coronavirus patients have suffered stomach aches before developing other official symptoms.
The American Journal of Gastroenterology published a study suggesting the virus could cause digestive problems such as diarrhoea.
It analysed data from 204 patients in China, discovering that 48.5 per cent of them had tummy issues such as vomiting, abdominal pain or diarrhoea when they were first hospitalised.
Teenager Dar'yana Dyson, from Maryland, Baltimore, US, died from a coronavirus-related inflammatory condition after suffering an upset stomach alongside other symptoms.
The 15-year-old's mum Kandace Knight told WBAL-TV: "It happened so fast. I never thought that taking my daughter to the hospital for stomach pain that I wouldn't be walking out of there with her.
"She was so beautiful, she was too good for this world."
Dr Diana Gall told the Express: "Digestion problems and changes in bowel habits - particularly looser stools and making more frequent trips to the toilet - are sometimes the first signs that you’re coming down with something, not just with this coronavirus.
"However, diarrhoea has been reported as an early symptom in patients who have later tested positive for Covid-19."
Eye infections
Doctors warned eye infections may be another sign of Covid-19.
Health officials think conjunctivitis develops in around 1% to 3% of patients, according to the American Academy of Ophthalmology.
Chelsey Earnest, a nurse at the Life Care Centre in Washington, said that red eyes are the ‘single most important’ sign that patients have COVID-19.
Speaking to CNN she explained: “They have, like...allergy eyes. The white part of the eye is not red. It's more like they have red eye shadow on the outside of their eyes.”
However, this does not mean you should panic if you see someone with 'pink eye'.
The American Academy of Ophthalmology said: “If you see someone with pink eye, don’t panic. It doesn’t mean that person is infected with coronavirus.
“But health officials believe viral pink eye, or conjunctivitis, develops in about 1% to 3% of people with coronavirus.
“The virus can spread by touching fluid from an infected person’s eyes, or from objects that carry the fluid.”
Brain fog
'Brain fog' is usually a symptom associated with 'long Covid' however some patients also experience it before being diagnosed with the disease.
Thea Jourdan told The Daily Mail that she first thought she may have been infected when she got a tickle in her throat and a headache.
The mum-of-three said: "Initially I felt exhausted, as if I was dragging myself through treacle and had no choice but to go to my bed. I had no meaningful cough and I wasn’t running a fever.
"I also had brain fog. I was unable even to fill out forms from the children’s schools. I just wanted to sleep, while trying to keep the kids safe and away from my quarantine area — my bedroom."
Others have also reported struggling to hold on to thoughts or remember things throughout the day.
Christy, a woman from Seattle who withheld her surname, told HuffPost, how her fever progressed into "sinus congestion, a headache and a debilitating 'brain fog' that made it impossible to focus.
Dr Hilary Jones said those who do experience the side-effect will be faced with a "crippling" inability to think clearly.
Fatigue
A WHO study looking at common signs found that the third most common symptom of coronavirus was a 'flatlining' feeling of fatigue.
Some 38.1 per cent of patients reported the symptom in the study, which was based on 55,924 laboratory confirmed cases.
Researchers previously described fatigue as one of the 'dark horses of Covid symptoms', alongside headaches.
Using data from the COVID Symptom Study app, the researchers created a list of the most common symptoms reported by patients in the first seven days after onset.
They said: “Our data shows that the most commonly experienced early symptoms are actually headache (82%) and fatigue (72%) - and this is the case for all age groups.
“Only 9% of COVID-positive adults aged 18 - 65 didn’t experience headache or fatigue.
Despite these high levels, only 1% of people reporting fatigue and/or a headache on the app ended up testing positive for Covid.
The researchers added: “While headache and fatigue are commonly found in people who have COVID (alongside other symptoms), having either or both of those symptoms alone is unlikely to be indicative of COVID.”