Long Covid: Why do some people have symptoms months after infection?

Long Covid is another public health crisis hidden inside the pandemic, medical experts have warned, with estimates of patients with the debilitating disease spanning more than 100m worldwide.

Scientists are in the early stages of finding treatments that could ease symptoms, target still unclear causes, and get people healthy enough to return to work.

A meta-analysis of studies by Penn State researchers found that more than half of the 236 million people with Covid-19 when the article was published – which has since grown to 275 million – had symptoms that lasted more than six months.

Amitava Banerjee, professor of clinical data science at University College London, said that even two years after the start of the pandemic, we are “still caught in the headlights”, focused on dashboards that track admissions and deaths in intensive care – but not the lengthy Covid crisis.

How is long Covid defined?

Long Covid is defined as exhibiting symptoms 12 weeks or more after diagnosis.

A recent British study found that one in three people admitted to hospital suffered from a long Covid one year later. Rachael Evans, a clinical scientist at the UK’s National Institute for Health Research, said the Covid-19 post-hospital study helped sort patients into subgroups and direct work to find new new drugs.

“This really highlights the urgent need for treatment surveys and healthcare support to improve recovery,” she added. “None of us think the long Covid has a mechanism and a cure.”

What are the symptoms of the long Covid?

Although patients suffer from a variety of symptoms, the most commonly reported are fatigue and breathing problems. Some also experience organ damage and in the PHOSP study one in 10 had clinically relevant cognitive impairment, often referred to as “brain fog.” Many symptoms resemble those of other post-viral illnesses, including coronaviruses.

Margaret O’Hara, administrator of the Long Covid Support patient group, fell ill with Covid-19 in April 2020, after helping in a coronavirus intensive care unit. She lived with the Covid for a long time for a year – then, after contracting the disease in October 2021, suffers again.

Research is being done on drugs to treat long Covid © Ronny Hartmann / AFP via Getty Images

“Simple fatigue doesn’t really begin to describe intensity,” she said. “It’s so weird. Sometimes I get up in the morning and within the hour it is as if I had been anesthetized. Like someone put a chloroform handkerchief over my mouth and I had to go and lie down.

Women, obese people, and those who were on invasive mechanical ventilation are all more likely to develop a long-term Covid.

It is unclear to what extent vaccination helps prevent long-term Covid – other than reducing the likelihood of developing acute Covid-19 – but self-reported data from the UK symptom tracking app Zoe suggests it is reducing half the risk.

What Causes the Long Covid?

Much remains unknown. However, the PHOSP study provided an important clue that lends weight to the hypothesis that the long Covid is caused by an ongoing immune reaction. He found that the patients had an increase in inflammatory markers. Researchers found that people with the most severe long-term Covid and those with brain fog had the highest levels of inflammation.

Sir Stephen Holgate, a professor at the University of Southampton and co-founder of Synairgen, a company that creates Covid-19 antiviral drugs, said MRI scans had also shown inflamed organs.

“The body turns on itself because of all this inflammation during the Covid period and attacks its own tissues. ”

There may be a genetic predisposition that determines who is most likely to suffer from this type of immune response, so researchers are conducting large genome-wide association studies that attempt to locate the genes that patients have in them. commmon.

Another hypothesis is that the virus attacks the energy reserves of cells, the mitochondria. Subgroups can suffer for different reasons, or both hypotheses can be true at the same time.

Are there any drugs that could be reused?

The UK’s NHS and major US healthcare systems have set up long-running Covid clinics, which often offer physiotherapy and mental health support, but have so far not had many pharmaceutical options.

Some doctors have tried using drugs with few side effects that they think could have an impact. These are as diverse as the symptoms, including antihistamines and cytokine blockers to treat inflammation, antacids, beta blockers, and blood thinners. A recent small study from Cambridge suggested that taking a combination of ‘friendly bacteria’ could help relieve long intestinal symptoms of Covid and improve overall well-being.

Banerjee aims to launch a study in the new year, modeled on the recovery trial that has identified useful drugs for treating acute Covid-19.

What are the future drugs in development?

Bill Hinshaw, general manager of Boston-based biotechnology Axcella Therapeutics, said there were few products in the pipeline for the long Covid – let alone targeting muscle fatigue and weakness. Axcella and the University of Oxford are developing a drug to reduce inflammation and restore mitochondrial function. They hope to have clinical trial data by the middle of this year.

“You have a certain amount of power in the battery,” Hinshaw said. “The virus comes in and takes control of the battery and. . . damages it so that the battery can no longer hold a charge properly.

Others focus on a subset of patients. For example, digital therapy pioneer Akili Interactive is making a game for people with brain fog.

PureTech Health is working on a drug for lung tissue damage, which is currently in a Phase 2 trial. Michael Chen, head of innovation at listed biotechnology in London, said nearly half of people with long-term Covid have suffered from shortness of breath, so “millions upon millions” could have lung scars.

“It’s a bit terrifying thought and a window into the public health crisis that could be long Covid in the future.”


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