Scientists may have finally found the cause of long Covid: Low iron levels after infection 'might be trigger of poorly-understood illness'

Experts may have found the cause of long Covid after discovering that low iron levels following an infection could be a key trigger.

An estimated 1.9 million people in the UK alone say they experience symptoms of long Covid.

These can include fatigue, shortness of breath, muscle aches and problems with memory and concentration – and last long after the initial Covid infection has subsided.

Now scientists believe that problems with iron levels in the blood – and the body’s ability to regulate this important nutrient – could be a key driver of ongoing issues.

And the discovery could point to possible ways to prevent or treat the condition.

An estimated 1.9 million people in the UK alone say they experience symptoms of long Covid. These symptoms can include fatigue, muscle aches and loss of smell

Shortly after the start of the pandemic, a team led by Cambridge University began recruiting people who had tested positive for the virus.

Over the course of a year, participants provided blood samples and it became clear that a significant number of patients would go on to have symptoms that persisted.

In the end the researchers focused their analysis on 214 individuals, around half of whom reported long Covid symptoms between three and 10 months after their infection.

They discovered that ongoing inflammation and low iron levels in the blood could be seen as early as two weeks following an infection in those individuals reporting long Covid many months later.

Problems with iron levels in the blood were detectable in the long Covid group regardless of age, sex or infection severity, they found.

Dr Aimee Hanson, who worked on the study while at the University of Cambridge and is now at the University of Bristol, said: ‘Iron levels, and the way the body regulates iron, were disrupted early on during SARS-CoV-2 infection, and took a very long time to recover, particularly in those people who went on to report long Covid months later.

‘Although we saw evidence that the body was trying to rectify low iron availability and the resulting anaemia by producing more red blood cells, it was not doing a particularly good job of it in the face of ongoing inflammation.’

Co-author Professor Hal Drakesmith, from the University of Oxford, said iron dysregulation is a natural response to infection.

‘When the body has an infection, it responds by removing iron from the bloodstream,’ he said.

‘This protects us from potentially lethal bacteria that capture the iron in the bloodstream and grow rapidly. It’s an evolutionary response that redistributes iron in the body, and the blood plasma becomes an iron desert.

Researchers discovered that ongoing inflammation and low iron levels in the blood could be seen as early as two weeks following an infection in those individuals reporting long Covid many months later

‘However, if this goes on for a long time, there is less iron for red blood cells, so oxygen is transported less efficiently affecting metabolism and energy production, and for white blood cells, which need iron to work properly. The protective mechanism ends up becoming a problem.’

The findings, published in the journal Nature Immunology, may help explain why symptoms such as fatigue and exercise intolerance are common in long Covid.

The researchers say the study points to potential ways of preventing or reducing the impact of long Covid by rectifying iron dysregulation during early infection.

One approach might be controlling the extreme inflammation as early as possible, before it impacts on iron regulation.

Another approach might involve iron supplementation - however as Dr Hanson pointed out, this may not be straightforward.

‘It isn't necessarily the case that individuals don't have enough iron in their body, it's just that it’s trapped in the wrong place,’ she said.

‘What we need is a way to remobilise the iron and pull it back into the bloodstream, where it becomes more useful to the red blood cells.’