With flu still causing chaos across the UK, it's easy to assume that any spluttering or sore throat is down to that... but it's not the only virus making Britons sick.
We revealed last month that it was possible to fall unwell with multiple seasonal viruses at once, with experts warning that our immune systems were being bombarded with not just flu but colds, RSV, norovirus, and covid.
But as well as the 'quindemic' which took hold over winter, there was another bug hiding in plain sight among the onslaught of germs, it's called adenovirus.
Adenovirus incredibly common - the NHS estimates that we all would have had at least one infection before we turn 10 - and because it's a virus, it's constantly mutating and evolving, meaning that you can catch it multiple times throughout your life.
Unlike flu, which peaks during the colder months, adenovirus is doesn't follow a seasonal path, and can be caught and transmitted all year round - and figures released last week by the UKHSA revealed that it's doing the rounds right now.
The UKHSA monitor weekly positivity data for common respiratory viruses including adenovirus, human metapneumovirus (hMPV), flu, covid 19 and colds.
Ian Budd, Lead Prescribing Pharmacist at Chemist4U, explained that many people suffering with adenovirus are actually unaware they have it, and just think they're under the weather.
'What we're seeing in the news, often called a 'mystery virus' or a fast-spreading throat/respiratory bug, lines up with what clinicians and public health bodies are seeing: adenovirus, a group of common respiratory viruses that circulate widely.
Compared to a cold, adenovirus can be more likely to cause fever and conjunctivitis
A mock-up of adenovirus travelling through the bloodstream
'Compared to a cold, adenovirus can be more likely to cause fever and conjunctivitis, and symptoms can last longer.
'And, compared to the flu, adenovirus infections typically cause less intense body aches and fatigue, and we don't have a readily available vaccine for it.
'These viruses aren't new, but with multiple viruses circling right now, more people are noticing symptoms and heading to their GP.'
While adenovirus infections are most common in babies and young children - the group most likely to be infected according to the latest figures are five year olds - people of any age can be affected.
Symptoms are usually mild and similar to those of a common cold, but it can cause other illnesses.
These include conjunctivitis, also sometimes referred to as pink eye, lung infections like bronchitis and pneumonia, croup which is described as sounding like a 'barking cough' in children, ear infections, and tummy upset.
Mr Budd added: 'Adenovirus is a family of viruses that can infect people of all ages.
'They're very common and usually cause mild illnesses, especially in children.
Adenovirus is highly contagious and spreads rapidly through nurseries, schools, hospitals, workplaces and care homes, with symptoms typically appearing between two days and two weeks after initial exposure.
And, unlike colds which can be spread via coughs and sneezes, adenoviruses can survive on surfaces and objects for a long time, meaning you don't need to be near someone to be infected, although people can continue to 'shed' the virus even after they have themselves recovered.
Because adenoviruses are viruses, they cannot be treated with antibiotics and you just need to wait for them to clear up on their own with rest and plenty of fluids - and that can take a couple of days or a fortnight.
Paracetamol is recommended in cases of fever and a humidifier or saltwater nose drops may ease congestion.
In more severe cases, particularly in very young babies, elderly people, or those with weakened immune systems, hospital treatment may be necessary.
Mr Budd said: 'Respiratory viruses like adenovirus tend to spread more widely in the winter and early spring when people spend more time indoors.
'With COVID-19 restrictions lifted and fewer people catching other viruses over the past few years, immunity in the community may be lower, leading to people becoming more susceptible.
'Adenovirus isn't a new virus; it's just showing up more often alongside other winter bugs.'
To protect against adenovirus, the NHS recommends making hygiene a priority with lots of handwashing and regularly disinfecting surfaces and shared objects.