As the weather gets colder, more people tend to get sick, with many complaining about having a headache, sore throat or a runny nose.
It is often difficult to understand which illness you have as some of the most common ones - such as Covid-19, flu and cold - can have very similar symptoms.
Since Covid emerged in Wuhan, China, in December 2019, there have been several strains that have made it even more difficult to tell the difference between the virus and other illnesses.
Covid is a contagious respiratory disease caused by infection with the virus SARS-CoV-2 - and it usually spreads between people who are in close contact.
The common cold is most often caused by rhinoviruses and spreads in a similar way as Covid-19.
Flu is also very infectious and can easily spread to other people by germs from coughs and sneezes, which can live on hands and surfaces for 24 hours, the NHS explains.
Several symptoms of cold, flu and Covid-19 overlap - especially sore throat, runny nose, cough, headache and body aches.
However, some more specific symptoms may signal your sickness is caused by one illness rather than the other.
For example, loss of taste and smell is a common warning sign of coronavirus infection, although some studies suggest it is now less common with the now-dominant BA.5 variant.
It is unusual for flu to cause a loss or change to your sense of taste and smell.
Infectious disease expert and professor of medicine, Albert Shaw, said: "Especially if you don't really have a runny or stuffy nose and you have this symptom, that probably is something that's more specific for Covid.
"And it's one we would see less so in someone with a common cold or someone with influenza."
Sneezing is a symptom more common with a cold than with flu or Covid-19, according to health experts.
The most common Covid-19 symptoms include high temperature, a new and continuous cough, a blocked or runny nose, feeling tired or exhausted, a sore throat, a headache, an aching body, feeling breathless, loss or change to smell or taste, loss of appetite, diarrhoea, feeling sick or being sick.
According to Professor Tim Spector, the following Covid-19 symptoms are also being reported by users of the Covid ZOE app: sneezing, a hoarse voice, chills, shivers, joint pain and sore eyes.
The NHS explains flu symptoms come on very quickly and can include a sudden high temperature, an aching body, feeling tired or exhausted, a dry cough, a sore throat, a headache, difficulty sleeping, loss of appetite, diarrhoea or tummy pain, feeling sick and being sick.
Symptoms of a common cold can include a blocked or runny nose, a sore throat, headaches, muscle aches, coughs, sneezing, a raised temperature, pressure in your ears and face, loss of taste and smell.
Treatment for these illnesses include resting and sleeping, keeping warm, taking paracetamol or ibuprofen and drinking plenty of water to avoid dehydration.
You should try and stay at home and avoid contact with other people to ensure you don't spread your illness.
It is also important to wash your hands regularly and wipe down surfaces to remove any germs.
The NHS advises patients to contact their GP or pharmacy if they are concerned or to go to A&E in an emergency.
Figures published last week by the ONS showed that Covid-19 infections are continuing to increase in England and Wales, though levels are still well below those reached during the BA.4/BA.5 wave.
In England, the number of people in private households testing positive for coronavirus in the week to September 17 was 857,400, or around one in 65 - up from 766,500, or one in 70, in the seven days to September 14.
The latest estimate for infections in Wales is 62,900, or one in 50 people, up from 39,700, or one in 75.
Covid-19 patient numbers are also starting to rise again.
The number of people in hospital in England with coronavirus stood at 7,024 on September 28, up 37 per cent week on week.
Patient numbers topped 14,000 in mid-July at the peak of the BA.4/BA.5 wave, after which they started to fall steadily.
This decline came to a halt in mid-September, however.
It comes as the chairwoman of the Covid-19 public inquiry to be "fair" and "thorough" - and to keep bereaved families and those who suffered at the heart of the investigation.
Former Court of Appeal judge Baroness Heather Hallett opened the inquiry in London saying she planned to investigate the UK's preparedness for a pandemic, the Government's response, and its impact on patients, NHS and social care staff and the public.
Potentially hundreds of thousands of people are expected to share their experiences via a formal listening exercise, while there will be a permanent tribute to those who died set up in the hearing hall.
A minute's silence was held for those who lost their lives, with Lady Hallett saying: "There's one word that sums up the pandemic for so many, and that is the word 'loss'.
"Although there were positive aspects of the pandemic, for example, the way in which communities banded together to help each other and the vulnerable, millions of people suffered loss, including the loss of friends and family members; the loss of good health - both mental and physical; economic loss; the loss of educational opportunities and the loss of social interaction.
"Those who are bereaved lost the most. They lost loved ones and the ability to mourn properly."
