We all know about severely infected people suffering from long Covid, but new evidence is showing that after even the mildest of Covid bouts, millions of us have been left with a legacy of debilitating ills – everything from loss of smell to brain fog, exhaustion and breathlessness.
Last week, the Duchess of Cornwall added herself to the long list of strugglers when she revealed that she is still battling the lingering side effects of mild Covid for which she tested positive in mid-February.
Camilla, 74, who is triple-vaccinated, told a Clarence House reception: "It's taken three weeks and still can't get shot of it. Probably my voice might suddenly go and I might start coughing and spluttering."
Such respiratory symptoms are among the most visible signs of the pandemic virus' unrelenting legacies, even for mild cases. Others are less obvious yet more worrying. Brain-tissue shrinkage and damage are the most alarming. Last week a study of more than 400 infected Briton's brains showed these changes occurring, on average 4.5 months after mild infection.
Researchers from the University of Oxford reported in the journal Nature how they saw reductions in grey matter in the regions of the brain associated with smell (the orbitofrontal cortex and parahippocampal gyrus).
On average, people who'd had only mild Covid symptoms also showed higher than normal rates of cognitive decline post-infection. This is linked to physical atrophy in part of the brain linked to thinking and problem-solving – which disturbingly may be a precursor to developing dementia.
Persistent physical symptoms, meanwhile, are driving people to buy expensive, dodgy and even dangerous quack "cures" from the internet, a study by the University of Birmingham warned earlier this year. It says that misinformation about dodgy salves is rife on social media platforms such as Facebook.
Experts meanwhile say that there are simple, cheap and safe things we can all do to help shake off the grim legacies of even the mildest Covid cases. Even if we think we're recovered fully, they warn, taking precautions for the long term could be crucial. Here's what to do if you suffer from...
Anosmia (loss of smell)
A Swedish study of more than 300 people confirms that anosmia is the most persistent problem that dogs people who have had even the mildest Covid symptoms. For a third of them, it can take at least six months for the problem to resolve.
It's not simply a loss of smell, however, but often a sensory derangement that can make food and drink taste repellently like rotten meat or chemicals. Fifth Sense, a charity for people affected by smell and taste disorders, estimates that 25,000 UK adults who have had Covid are affected.
Scientists are still debating the precise causes. Research from a collaboration of American universities, published in February in the journal Cell, suggests the coronavirus attacks cells in the nose that support smell-sensing neurons, effectively short-circuiting them.
Dr David Strain, a senior clinical lecturer at the University of Exeter who specialises in viral infections, explains that it is not certain yet how the brain shrinkage may be involved. "This atrophy might itself cause the loss of smell. Alternatively, loss of smell signals from the nose might make smell-processing areas of the brain redundant, so they are shrinking as a consequence."
The hope, Strain says, is that we can retrain our brains' smell centres to work properly again. Indeed Fifth Sense, along with experts at the University of East Anglia, has created an online guide for a "smell training technique" that may help anyone who has experienced a loss or change in their sense of smell.
The training normally involves sniffing at least four distinctive smells, such as oranges, coffee or garlic, twice a day for several months in order to retrain the brain to recognise different smells.
Carl Philpott, professor of rhinology and olfactology at the University of East Anglia says: "Smell training is cheap, simple and side-effect free. It aims to help recovery based on neuroplasticity – the brain's ability to reorganise itself to compensate for a change or injury."
In a similar vein, Hungarian olfactory experts at Semmelweis University in Budapest are using "Sniffin' Sticks" infused with a variety of aromas to diagnose the problem. They then treat patients with an olfactory training method that involves inhaling four basic smells from essential oils – eucalyptus, cloves, lemons and lavender – once or twice a day for between four and six months.
Problems with "brain fog" affect a quarter of people recovering from Covid, according to the Office for National Statistics (ONS). Troubles with sustaining attention, remembering things and planning ahead can persist for up to nine months after mild symptoms, according to a January study of 135 people by neuroscientists at Oxford University.
Such problems may often go unnoticed by the people themselves, the research found. But these insidious problems may lead to serious trouble, warns Strain: "A recent study of 162,000 Danes who'd had only mild Covid symptoms found that their rates of cognitive impairment, which can be a precursor to dementia, were two-and-a-half times higher than people who hadn't had Covid."
Strain hopes that post-Covid we can train our brains out of brain fog, not least by doing cognitively stimulating activities – from doing word games to learning a new language. Research also shows that having regular social interactions is important, so it's high time to revive all your old networks post-lockdown.
However, it is important not to overdo things, Strain adds: "We see in Covid that mental strain can cause exhaustion and physical malaise, perhaps by triggering inflammation in the brain and then subsequently in the body. By all means, do try brain exercises, but be aware that this may trigger physical symptoms. Pushing yourself is not a virtue here."
Physical fatigue afflicts more than half of people who have had Covid infection, ONS research shows. After an enforced lay-up with only mild symptoms, it's tempting to rush back into vigorous exercise as a way of speeding back to full recovery.
However, this can backfire badly, warns Dr Jeremy Rossman, the senior lecturer in virology at the University of Kent. "After a virus, you are prone to suffering post-exertional symptom exacerbation," he says. "When people who have Covid over-exert themselves, they can spark a dramatic worsening of their old symptoms – and new post-Covid symptoms may also develop."
Over-exercising just once after a virus can leave you so exhausted that you can't exercise again for days or weeks. One step forwards, two steps back.
Rossman cautions: "Be very careful. Have six weeks of full rest and then slowly look at your activity. Work initially within a dramatically reduced envelope and do less than you think you can. That is definitely not suddenly doing 'just 15 minutes at the gym', it might be about taking a short walk."
He adds: "Beyond this, simple beneficial activities involve keeping well rested and well hydrated, and eating a healthy diet rich in vitamins. As for any particular supplement or diet regime, the evidence just isn't there to support any."
Shortness of breath affects more than a third of people recovering from Covid. "Breathing exercises are the one physical activity that I would definitely recommend post-Covid," says Rossman. "Respiratory rehabilitation can be very useful for some patients, although it doesn't necessarily help everyone and it is definitely not a cure."
The NHS recommends trying this simple daily deep-breathing exercise: take a long, slow, deep breath inwards, through your nose. Keep your chest and shoulders relaxed. Breathe out gently and relaxed, like a sigh. You should do between three and five deep breaths.
Some people find it helpful to hold their breath for 2-3 seconds at the end of the breath in, before breathing out. Try the deep-breathing exercises both with and without holding your breath and see which works best for you.
Even people who think they are fully in the clear after mild Covid might not be, says Rossmann.
"Some cardiovascular studies, for example, have shown long-term structural effects on the hearts of people even if they don't have persistent symptoms. There is a risk down the line among people we currently consider to be recovering OK. We really don't know at the moment.
"It is probable that multiple organ systems and processes are involved. But we don't really know how many of these changes persist in people who don't currently show any symptoms."
To be on the safe side, people in midlife and older should consider getting full medical examinations post-Covid, he argues. "Some of the long-term effects can be diabetes, heart disease or kidney damage. These are add-on diseases, but we know that the risk of developing them post-Covid can rise substantially. At the moment we can't say that 'recovered' means you are out of risk."
'Cognitive therapy helped me beat brain fog'
For nearly two years, Rachel Robles has been battling the crippling effects of brain fog after catching Covid. As a senior strategist at Indeed.com, she was used to giving presentations at work – but suddenly she found herself struggling to recall simple words.
"Sometimes, I would read a page in a book and not understand the sentences, or have a hard time following a conversation with someone because the words didn't have a meaning to me," she says. "I've described brain fog as the equivalent of trying to solve a problem without a necessary clue that everyone else seems to have. It feels like you've taken heaps of sleep medication, turning your environment into a cloudy, murky maze."
In August 2021, Robles sought treatment at a concussion clinic where an MRI scan showed that the virus had damaged some of the small blood vessels in the brain. She was put through an intensive program of cognitive therapy and neuromuscular therapy – which encompassed breathing techniques, balance exercises, and head massages to improve fluid movement through her head and body – to try to encourage the growth of new neural connections.
"I worked with multiple speech-language pathologists," she remembers. "We would play card-sorting games while I answered questions about my life simultaneously, and they taught me tricks to memorise up to 30 words at a time. One of the most beneficial exercises I did was in cognitive therapy when I had to play a word-sorting game while listening to background music. One of my most severe symptoms was sensitivity to sounds and distractions, and that exercise allowed me to reintegrate sounds back into my brain."
While Robles has not fully healed from long Covid, as she still suffers from symptoms such as eczema and migraines, her brain fog is greatly improved.