Long COVID is no longer a theory. According to a new review article published in Nature Reviews Microbiology. Researchers have now identified more than 200 different symptoms, spread across multiple organ systems. Fatigue, brain fog, post-exertional malaise, new conditions such as heart problems, diabetes, blood clots, stroke – all have been reported and many more.
According to the CDC’s definition, long-term COVID occurs when people experience new, recurrent, or persistent health problems more than four weeks after their acute COVID infection. More generally, long-term COVID is an emerging condition whose toll continues to grow, and while much has been learned about it, much remains unknown — including the best ways to treat and prevent it.
“I wish we had these answers,” said Dr. Eric Topol, a leading COVID expert and the senior author of the comprehensive article, which included more than 200 peer-reviewed studies. “At the moment we have a long breath in mechanisms and a shortage in treatment. That’s the summary of everything.”
Here, Topol, who is also executive vice president of Scripps Research in San Diego, lays out the boundaries of what we know about long COVID and the urgency with which government and researchers must act.
This conversation has been edited and shortened for clarity.
Can you provide a general working definition of long COVID and describe who it affects and how?
Long COVID is the perseverance of significant symptoms long after the virus would have had its acute illness. The problem with this is that it is quite a mosaic of different organ systems and symptoms that may be involved. It can lean in one direction, like the autonomic nervous system, or it can lean towards the cardiovascular or respiratory system. It can take people who are fully functional, athletic, and healthy, and make it difficult for them to get out of bed or even walk a block.
Are children affected in the same way?
Fortunately, they are not so inclined to get it. It may follow the same pattern, but it’s not quite as common.
Are you more likely to get long COVID if you had a severe illness rather than a mild illness?
That’s a very good question. It seems that if you’ve had worse COVID acutely, more organ systems will be involved, but that doesn’t mean if your initial infection was mild you’re off the hook. You can still get things like a stroke, a deep vein thrombosis (blood clot), or an arrhythmia – things like that. It’s just not as common to have those hits to different organ systems as it is for the people who had severe COVID and had to be hospitalized.
Does vaccination reduce the risk of long-term COVID?
Vaccination clearly reduces the severity and frequency of long-term COVID. The only debate is to what extent. (Estimates ranged from 15% to 50%.) It doesn’t completely prevent it. There’s only one way to avoid long-term COVID, and that’s to never get COVID.
Are those infected with the new variants like XBB.1.5 more or less likely to develop long COVID?
It seems there’s a lower chance of getting COVID for a long time, but we don’t know if it’s because of the variants or because people have had more vaccines and more natural infection immunity and combinations of those.
What do the numbers look like globally and in the US? How many are currently affected by long-term COVID?
It’s hard to know exactly. Some people have had COVID for a long time and are recovering or even fully recovered, while others have had it for three years. But most estimates are that 3% of the population — which would put us at 10 million — is the minimum number of people in the US with long-term COVID. The question is how much more than that? Is it 15 or 20 million? And then there’s clearly a spectrum of severity.
A woman tweeted that she had run over 130 marathons, cycled Category 1 climbs and climbed Kilimanjaro, but that since COVID her husband has had to “carry me to the bathroom due to neurological issues.” Do we have any idea of the long term spectrum and how much of the long COVID is debilitating?
There are many people like the woman you just described, and it’s more appropriate to be women in that serious group. We know that women are more susceptible to autoimmune diseases, such as lupus, Sjogren’s syndrome, systemic sclerosis, etc., so that’s part of it. Men can have severe cases, but it is more likely to be in women.
What are some of the other proposed mechanisms of long COVID?
Inflammation is a common thread in everything. It can affect the autonomic nervous system, which is how you can get the neuropathy of postural orthostatic tachycardia syndrome [an abnormal heart rate increase that occurs with standing]. It can also affect the lining of blood vessels, which can cause you to have clotting problems, and it can also be caused by significantly affecting the gut microbiome and perpetuating inflammation.
What do we know about reinfection? If someone has not had a long COVID initially, are they at risk?
That is a very important area. With a second or third infection, you can unfortunately still get COVID for a long time. Just because you’ve had an immune response from an infection doesn’t prevent it. It’s probably less common just because part of the long COVID story is that[patients]don’t have an ideal immune response, whether it’s an insufficient response or a hyperresponse. But it’s not like the second infection is a higher risk (for long COVID) than the first. This is very often misinterpreted.
Can you talk about what was initially called brain fog, but what we now recognize could be true cognitive impairment?
Well, there are many parallels with “chemo brain.” It’s not that the virus directly infects brain cells, but it leads to inflammation in key brain areas that are affected, such as memory and executive function. This is very disturbing because this is a very common symptom – it’s high on the list of what people report. We don’t have a treatment to take care of this, and many people may have it.
Some people say the cognitive dysfunction resembles Alzheimer’s – or is it another form of dementia? Or is it that we just don’t know?
I would say we just don’t know. But that’s the concern. What if this is progressive? What if it simulates what we see in neurodegenerative diseases? I am an eternal optimist so I hope the body is remarkable and will fight it and turn it around.
There have been some reports of COVID being associated with erectile dysfunction, lower sperm count, and low testosterone. Is male fertility a concern – or female fertility for that matter?
We know there are clear effects there. That has not been sufficiently researched either, but it certainly deserves study. It could be linked to less fertility in men, but we don’t know. Because so many young men have been affected by COVID and long COVID, this is a concern, but there hasn’t been nearly enough attention to those impacts as they affect the heart, lungs, and brain.
Could the antiviral drug Paxlovid help those affected?
There is some data showing that some people who had had COVID for a long time and who took Paxlovid had their symptoms improve significantly. These are more anecdotal at this point, but it lends some credence that in some people the persistence of the virus – the reservoir of the virus and its remnants – could be remedied with a drug that inactivates the virus. The question is will it help a small percentage of people, like 1% or 2%, or will it help more?
Have there been large-scale trials to test its effectiveness?
No, there haven’t been. And there should be. There’s no excuse for this… We need to double down, quadruple in doing the right trials, testing all the candidate things we’ve listed in the article. Paxlovid is clear, and naltrexone — it’s clear that we should be doing these studies, so there’s just no excuse. With the amount of money the NIH has spent on this, we should have done these trials by now, final trials. People are desperate, they need treatments. The predators hunt them to get this or that treatment, but nothing has been proven to help yet.
Why doesn’t the US government coordinate a more forceful response, or why don’t drug companies jump into this market and conduct large-scale trials?
It is an incredibly important and fertile field in which effective treatments are defined, but the mentions in it are very scarce. Some of the possible treatments are very impractical, such as hyperbaric oxygen chambers or apheresis. These are very expensive, hard to get treatments. We need something that is practical, highly effective and widely accessible.
Would you consider long COVID a national emergency in its own right?
There are a large number of people who are disabled or have their status affected by this, (but) it was more of a slow train than an emergency. It has not been respected enough… At this point, the response should be: let’s do everything we can to prevent infections. Most importantly, what about these millions of people who are hurt, who are still suffering – how can we help them get their lives back?
Do you think there is an end date for long COVID?
We won’t know for another 10 years, right? In 1918, with the flu pandemic, Parkinson’s showed up about 15 years later. It was not visible in the early years. We don’t know if we’re going to see things that haven’t manifested yet because the longest duration right now is less than three years.
Knowing that we all want to move on with our lives, to remain fertile and not suddenly drop dead, how careful should we be?
We cannot capitulate to the virus and abandon all our guards. Getting boosters, taking precautions when indoors in public gatherings, improving our ventilation – we have things that can help prevent infections. At this point, people have moved on, but for those who haven’t had COVID or those who get a re-infection, it’s not necessarily benign. You hope it does, but perhaps the most important thing we haven’t discussed is the gamble part. We just don’t know who is really at risk. People want to reject this. But this is an inconvenient truth, long COVID.