Coronavirus news & views

Parkinson’s Disease—An Unexpected Ravage of COVID?

Thus, (tho, ‘tis Life’s great Preservation) many oppose Inoculation.

-Benjamin Franklin, Poor Richard’s Almanac, 1737

SARS-CoV-2 and its disease, COVID, are very strange. They have given us black toes, lungs like chocolate pudding, long-term fatigue, depression, death, and vaccine deniers. It has been quite a ride. And we are learning that having COVID also puts one at risk for other non-COVID maladies…like chocolate pudding lungs was not enough!

In previous posts, I wrote about the clear link between new-onset type 2 diabetes arising in many patients following COVID. There also is suspicion that cancer might increase down the road due to CoV-2 inactivation of a cellular gene that puts a brake on cancer, P53, in COVID patients. Inactivate that gene and you release the brake on certain cancers. Therefore, there is concern that some COVID patients will experience an elevated incidence of cancer in the future.

New research now raises a real concern that COVID patients might also be at increased risk for developing Parkinson’s disease. Parkinson’s arises when neurons deep in the brain that produce a critical neurotransmitter, dopamine, begin to die off leaving a dearth of this critical chemical that sends signals between neurons. It is like cutting a phone wire. Crucial communications cease.

The study conducted in collaboration between scientists from Weill Cornell Medicine, Memorial Sloan Kettering Cancer Center, and Columbia University College of Physicians and Surgeons was published in Cell Stem Cell last January. Investigators took human induced pluripotent stem cells and coaxed them to become brain cell progenitors that could form into human brain organoids in tissue culture. Such small, nascent “brain-like” structures contain a variety of functional neural cells. They were exposed to the CoV-2 virus, which was shown to preferentially infect and selectively cause the dopamine-producing cells to shut down.

While brain autopsies of COVID patients have not revealed direct COVID infection, they have found unique gene patterns associated with cell senescence, which was especially profound in areas rich in dopamine-producing neurons. This also supports the notion that COVID disease contributes to neurological problems that could cause Parkinson’s disease.

Putting these two findings together is complicated at this time, but they strongly suggest a direct involvement for one or more mechanisms resulting from CoV-2 infection in causing the myriad neurological symptoms that have been seen in COVID patients, and maybe other neurological problems like Parkinson’s not yet attributed to COVID.

Bottom line: CoV-2 is a nasty bug and COVID is a nasty disease. It seems that getting vaccinated not only protects you from nasty flu-like disease and death, it can also protect you from the following:

1. long COVID
2. type 2 diabetes
3. maybe cancer
4. and now, maybe Parkinson’s disease

Why would anyone not want to avoid these? Get the shots!

Interesting addendum: The studies showing that CoV-2 virus can selectively infect dopamine producing neurons went a step further. They also tested a large panel of drugs already approved for other health problems to see if any could unexpectedly protect these critical cells from infection. Sure enough they found three drugs that protected the neurons: Riluzole (used to treat Lou Gehrig’s disease) Metformin (commonly prescribed for diabetes management), and most interesting to me, Imatinib, or Gleevic (used for treating certain leukemias and cancers).

I say this is interesting to me because of my own research beginning at UCLA in the mid-80s, and extending to the University of Wisconsin into this century. My research focused on certain leukemias that carry a specific chromosome abnormality that appears in 99% of patients with chronic myelogenous leukemia (CML), and in fewer patients with acute lymphoblastic or acute myeloblastic leukemias (ALL and AML respectively). When I began studying this, the presence of this chromosome aberration was a death sentence. There was no effective treatment. Patients did not survive long. We identified the specific genetic abnormality, cloned the abnormal gene, sequenced it and found it was parts of two genes stuck together. Most importantly, we also described the enzymatic pathway in cells that it screwed up. All this eventually led to the development of a drug that tamed the misbehaving enzymatic pathway so that now >95% of patients with these diseases are fully cured with medicine that is pretty easy to tolerate. What once was a death sentence is now an easily treated disease. Knowing that makes me feel pretty good.

The drug that cures leukemia patients from what once was a lethal disease is called Imatinib; one of the drugs found to also protect dopamine producing neural cells from CoV-2 virus destruction.

That too will make me feel pretty good if it also happens to prevent neurological problems in COVID patients. Who would have guessed? This is the unpredictable way science often works.

‘Tis The Season To…..Mask Up Again??

"It's a bug hunt!"

-Private Hudson, in “Aliens”

"Influenza-like illnesses" are increasing at an alarming rate across the country. Yup, ‘tis the season for respiratory diseases and we have more than one to worry about. In years past we mostly worried only about the flu and, sometimes as an afterthought, colds, which aren’t of much concern. But in late 2019, a brand new and very weird bug appeared on the scene, SARS-CoV-2 that caused COVID. It seems that the bug and disease will be an annual guest from now on. This year, we also see a surge of a third bad bug, respiratory syncytial virus, or RSV. All these viruses cause what have been collectively labeled “flu-like illnesses” and together they seem to be worse this year than recent years. The CDC reports that hospitalizations for flu-like illnesses have been steadily rising and that the peak is still to come.

As a result, we are beginning to see increasing reports of a return to local mask mandates. In my own community of Madison, Wisconsin, two major health networks just announced their return, like a bad TV rerun. This includes the University of Wisconsin Health network, where I receive health care. Glad I kept a few masks on hand. What’s in your glove compartment?

I also have read where some grocery stores are now requiring masks. Some stores only require masks on certain days of the week so that customers can select to shop on mask-required vs mask-optional days. Some colleges and large companies reportedly also are beginning to require masks again. So far these mandates are very local and are not a national phenomenon. It is feasible that mask mandates in public spaces and especially for travel could increase if infections and hospitalizations get more serious.

As I often say in these blog posts, “we will see.”

Why is the flu and RSV, which have been around almost forever now causing more than their usual problems? A hint was presented in a blog post I published about a year-and-a-half ago, “What Happened To The Flu And Other Respiratory Diseases?”  In that apparently prescient post, I reported that the world had seen a huge reduction of all infectious respiratory diseases due to the protective non-pharmaceutical interventions (masking, sanitation, isolation, quarantines, closings, etc.) designed to physically protect people from the new coronavirus. They were so effective that some strains of other common infectious viruses are thought to have gone extinct!

That is great news! But, it also means that the world also missed its regular natural booster of common bugs and our herd immunity to them waned. Our youngest were never exposed to those bugs and the rest of us became less resistant to future exposure and that future is now. We are now paying the piper for that lapse in a “bug boost.” Hence, flu and RSV temporarily are having their way with us and enjoying it. At least they are not nearly as nasty as the coronavirus initially was and still could be with a couple of insouciant genetic tweaks.

“Influenza-like illness,” is a catch-all term coined by the CDC to corral COVID and the other two viral diseases. Together, the three have reached an epidemic point in the US and other places across much of the world. The Figure below shows that the US epidemic is currently hitting Southern States the hardest, but expect it to migrate Northward in the next few weeks.

What do the different colors in the Figure mean on a practical level? I can offer one anecdotal example. According to the map, New Jersey, while not a Southern State, still is being hit hard. A family doc wrote about a week ago that all the hospitals in his health system are at capacity. He was unable to send a patient to the preferred ER because its hospital was full due COVID, flu and RSV cases. And the patients with these flu-like respiratory infections who were filling the beds were not necessarily elderly. Most are in their 40’s-50’s. Unsurprisingly, the hospitals and clinics in his health system again require masks. Their staffing is becoming a critical issue as providers also become ill and turn into patients. This is becoming too reminiscent of the early stages of the COVID onslaught when hospitals where overwhelmed and medical personnel were dropping like flies. So far, this experience is sporadic across the US. But, it is becoming concerning.

Outpatient Respiratory Illness Activity Map Determined by Data Reported to ILINet

This system monitors visits for respiratory illness that includes fever plus a cough or sore throat, also referred to as ILI, not laboratory confirmed influenza and may capture patient visits due to other respiratory pathogens that cause similar symptoms. From the CDC.

The incidence of RSV is high. RSV hospitalizations have increased 60% nationwide over the past four weeks. A couple of deaths in children have been reported in my state. The vaccine for RSV is brand new this year and recommended for people over 65 and for kids; i.e., those at highest risk for severe disease. It definitely is worth it.

Flu is moderate right now, but expect it to soon blossom. Hospitalizations among all age groups increased by 200% for influenza in the past four weeks but still remain below Covid-19 and RSV hospitalizations. For now. They are expected to increase as the peak flu season has yet to arrive.

And then there is our relatively new friend, COVID. On a national level, COVID virus transmission is “very high.” After the post-Thanksgiving surge, as determined by monitoring viral loads in wastewater samples (“take-your-kids-to-work” days in that profession must be fun!), virus levels plateaued. But expect another sharp rise after the Christmas/New Year’s holidays. We have consistently seen this pattern in previous years.

Cov-2 is one of the most mutable viruses that the world has inflicted on us. That means we are constantly seen new variants arising. Surprise, the Omicron subvariant JN.1 is coming onto the scene. It’s the spawn of variant BA.2.86, which was discovered over the summer and was concerning because it came out of nowhere with a whopping 35 mutations in the spike protein (the more mutations, the greater the chance for another very nasty bug). While BA.2.86 caused a comparatively mild disease, it quickly mutated to JN.1 with just an additional single change in the spike protein that made it much more infectious, but it still remains fairly mild. With just one mutation, it became the fastest-spreading CoV-2 variant in the past two years. With all its changes, JN.1 is so different from its Omicron grandparent that there is considerable scientific debate about whether JN.1 should be given its own Greek letter designation, Pi. A weighty debate indeed.

But, a bigger question is whether COVID hospitalizations will follow wastewater sampling trends that show JN.1 (or Pi) viral levels surging through the world, especially in the US where vaccination rates are low. It is concerning that the UK and Singapore, which have high vaccination rates, are now seeing a steep increase in hospitalizations due to JN.1 (or Pi). So why not expect the same or even worse in the undervaxed US? Last week, the CDC warned about such a potentially huge impact due to the wretched combination of low US vax rates and the highly infectious JN.1 (or Pi) virus. As Private Hudson (aka Bill Paxton) in the movie Aliens might say, thanks to the antivaxers, “Game over, man! Game over!”

Also of new concern is that some scientists are now beginning to believe that COVID infection could be damaging our immune systems. If true, that could make infected people even more vulnerable to the other bugs out there such as flu, RSV, and others including bacteria and fungi. COVID could also cause immune dysregulation leading to new-onset autoimmune diseases. So get your COVID vaccines! They can protect you against illness beyond COVID!!

Finally, another concern is that the rapid home tests for COVID are proving to be only 30% reliable very early after infection before symptoms start. In other words, if you believe you have been exposed to COVID, but your home test comes up negative, don’t necessarily believe it. Retest yourself 24, or preferably 48 hours later or when you show symptoms like a fever, cough, etc. If that second test also is negative, you have pretty good confidence you are COVID free and have some other bug.

The pragmatic bottom line. There is a lot of coughing, sneezing and other respiratory distress going around, and it will increase in coming cold weeks as we bundle up and crowd around others indoors. To improve your odds of staying healthy, remember these things:

• Limit your time around indoor crowds.
• If you have indoor gatherings, crack your windows and bring out the fans to increase air circulation and air exchange with the outdoors. There is very good evidence that good ventilation really matters and that the amount of viruses we breathe in makes a big difference in terms of whether we get sick and how sick we get. It is worth a few extra dollars on the heating or electricity bill to avoid nasty illness.
• Room air filters are also a good idea.
• Get vaccinated!
• Wash your hands often.
• If you do get sick, STAY HOME! I have always hated the “brave” soul who came to work with a cough and sneeze. Don’t share your agony!!
• And there are the good old fashioned masks for use in crowded places, especially in auditoriums, on planes, and other packed indoor situations. I don’t care what the naysayers say about masks, they are flat wrong. They don’t think twice when a store sign requires shoes and shirts to enter. So why do masks bother them so much? They WORK as I have written here before, over and over. Empirical evidence proves masks work. That is why the entire medical profession continues to use them.

Finally, as I have repeatedly admonished, please get vaccinated. Vaccine and booster uptake for all three viruses has been dismal this year. Failure to vax is a major driver in the surge of the flu-like respiratory diseases we are seeing. If you have not gotten vaccinated for all three circulating viruses, why the heck not?? It is way better to prevent disease than to treat disease. A sore arm is much less of an inconvenience than suffering the flu, RSV or lying in a specialized hospital bed turned on your stomach breathing with a ventilator because of COVID.

As I have written in these pages, having COVID can be worse than any flu you ever had. It also puts adults at risk for dealing with weeks of long COVID and getting new-onset diabetes and immune dysfunction. COVID also is much worse than the flu for many kids and puts them at risk for multi-system inflammatory syndrome (MIS).

Why risk what can be prevented by a simple vaccination?

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The Long Haul, Part 4: The Cost of Long COVID In Terms Of Individual Health And Quality Of Life

Surviving COVID-19 is one thing, recovering is another.

My frustration with those who would minimize the impact of COVID-19 is reaching an apex. I constantly have to deal with their baseless rationalizations that “it is just a cold,” or “it only kills 0.01% of people” (actually the number is 2% around the world), etc. And I constantly reply to these iconoclasts that COVID has become, by far, the leading killer in the US. I also explain over and over that treating simple mortality percentage as the only relevant statistic to consider is falderal. For example, the Spanish flu also killed “only” 2% of those infected, but in just 24 weeks, that virus killed more people around the world than were killed in WWI AND WWII together! The percent figure is meaningless without considering the percent of what. Why do they continue to ignore the devisor and, hence, the total number of deaths?

A small percentage of a very large number is, in fact, another large number.

Those who wish to downplay the significance of the pandemic only focus on this mortality percent, but mortality is NEVER the whole story for any pandemic. A serious person will also consider the morbidity caused by the disease. In fact, the major CDC publication on health in the US is called the Morbidity and Mortality Weekly Report. Notice that it considers both morbidity and mortality, and further notice that morbidity is listed first in the title. I have made three prior posts in this series on Long COVID, about the significant lasting morbidity of COVID-19. You can see these posts here, here, and here. In those posts, I shared data showing that some ~10-30% of COVID survivors suffer serious health problems that last months.

In those posts, I mentioned the cases of a young, healthy MD, and of a young, healthy journalist, both of whom struggled with long COVID, and how it affected their careers and cost them thousands of dollars in out-of-pocket expenses for the dozens of tests and doctors they needed. In an article in Maclean’s magazine, a reporter interviewed many Canadian long COVID patients and heard how their lives have been turned upside down. They reported that they are unable to live like they used to and care for their families, do anything mildly strenuous, or even cook their meals. They spend long stretches of time in bed. Many of those interviewed had not returned to work several weeks after recovering from the acute disease.

Anecdotes like these have been repeated millions of times around a world that, according to the Johns Hopkins University COVID tracker, has seen more than 330 million cases of COVID (and this is a significant undercount since many countries do not record these data well). Research has corroborated these anecdotes.

+++

Common long-term symptoms include debilitating fatigue; respiratory problems; and “brain fog.”  Other common symptoms include compromised function of the heart, and kidneys, which sometimes require transplantation. Wide-spread clotting problems can cause significant illness and even limb amputation. There also are frequent neurological and neuropsychiatric symptoms as highlighted in Part 3 of this series. Surprising manifestations continue to emerge, such as new-onset diabetes.

Lung scarring often occurs in patients who experienced COVID-caused acute respiratory distress syndrome (ARDS), a common problem seen in acute COVID patients who required ICU care. ARDS is a serious respiratory problem that can be caused by different respiratory viruses and other things. About a third of patients with ARDS arising from any cause were unemployed 5-years later because of their lung damage. It is fully expected that patients with COVID-related ARDS will be found to fare similarly.

There also is the dysfunctional immune response common in many moderate to severe COVID cases that can cause long-term multi-organ damage, particularly in the liver and kidneys. It can also disrupt coagulation control of the blood, sometimes leading to amputations, mostly in patients in their 30s and 40s. It was reported that amputations due to vascular problems have doubled since the CoV-2 virus arrived. Compromised coagulation control in COVID patients can also precipitate adverse cardiovascular events such as heart failure, or hemiplegia due to strokes. Data from the COVID Infection Survey on long-COVID suggest that the risk of major adverse cardiovascular events and long-term illness is about ten times higher in COVID patients (even after mild COVID) compared to non-COVID matched controls. A Dutch study found that 31% of COVID ICU patients suffered thrombotic complications. These problems can unexpectedly pop up in people who had completely recovered from COVID.

A global survey tallied 205 different symptoms across 10 different organ systems that can persist after COVID infection has cleared. Typically, these manifold long COVID symptoms do not appear in isolation, but in multi-symptom clusters. A long hauler typically has several of these problems at a time.

While it is estimated that overall, 10-30% of COVID patients become long haulers, reports on the number of people suffering long COVID vary widely. Depending on the report, anywhere from 30-90% of COVID survivors suffer long term health problems. And even at the lower end of that range, 30% of over 330 million people world-wide who have been infected is a very large number. It represents an enormous personal toll in terms of lost health and diminished quality of life. Some of these reports are summarized below.

• Half of 70,000 hospitalized UK COVID-19 patients experienced long-term complications, according to a study published in July. Complications occurred regardless of age group: For instance, 25% of adults aged 19-29 developed complications, as did 33% of those aged 30-39. Complications affecting the kidneys and respiratory system, liver injury, anemia, and arrhythmia were the most common.
• Many COVID-19 survivors require extensive and prolonged rehabilitation. An European study found about one-third of 1,837 non-hospitalized COVID patients (i.e., those with mild disease) needed a caregiver three months after their symptoms started.
• In April the CDC reported in its Morbidity and Mortality Weekly Report that 69 percent of nonhospitalized adult COVID patients in Georgia required
• one or more outpatient visits 28 to 180 days after their diagnosis.
• A study published last February in the Journal of the American Medical Association found that roughly one-third of 177 people who had mild COVID disease not requiring hospitalization reported persistent symptoms and a decline in quality of life up to nine months after illness.
• 70% of people hospitalized for COVID-19 in the UK had not fully recovered five months after hospital discharge. They averaged nine long COVID symptoms requiring continued medical care.
• A study in South Korea found that 90% of patients who recovered from acute COVID experienced long-term side effects.
• According to a report in the journal, Lancet, 75% of people hospitalized with COVID-19 in Wuhan early in the pandemic, reported continued problems with fatigue, weakness, sleep problems, anxiety and depression six months after being diagnosed with the disease. More than half also had persistent lung abnormalities.

Data like these have been commonly reported around the world, pointing to a more chronic and expensive health problem than seen with the flu or common cold, which often is caused by different coronaviruses. A July 2021 article in Scientific American talked about how all of this indicates that long COVID will cause a “tsunami of disability” that will affect individual lives as well as create enormous strain on the health system. Consider the numbers: More than 60 million Americans (this is an underestimate since many COVID cases are not reported) have been infected with the CoV-2 virus. Therefore, if only 30% of these suffer long COVID, we are talking about 20 million long haulers and counting.

The related health care and disability costs of all of this are also still being calculated. How many “long haulers” will not be able to return to work for months, or at all? How many will need short-term disability payments, and how many will become permanently dependent on disability programs? As increasing numbers of younger people become infected, will we see a generation of chronically ill? This then moves us to consider the economic and financial cost of long COVID, which will be the topic of the next installation in this series.

Stay tuned.

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The Long Haul, Part 2: What Is Long COVID?

In the 1890s one of the biggest pandemics in recorded history, known then as the “Russian flu”, swept the world and killed one million people (for perspective, that is out of a world population about ¼ of today’s population). That “flu” is now thought to have been a novel coronavirus. Like the current coronavirus, SARS-CoV-2, the Russian “flu” was a new human pathogen so few people had any natural immunity to it and it was quite lethal. Not only that, but as the pandemic waned, it left in its wake a global wave of long-lasting neurological problems in the survivors. A similar long-lasting post-acute disease wave followed the next big pandemic, the “Spanish” flu of 1918 (which really was due to the influenza virus). The common symptom following the Spanish flu was lethargy so bad that in Tanganyika (modern-day Tanzania), for example, it caused a famine because people were too debilitated to pick the harvest. Other viral outbreaks, including SARS, MERS, and Ebola, also have been associated with long-term sequelae in survivors. However, today’s long COVID complications are far more common and far more variable than the persistent symptoms following these other viral pandemics. The variety of unrelated long COVID symptoms has flummoxed doctors hard pressed to diagnose and, hence, treat the constellation of chronic problems that appear in each patient.

As I wrote in Part 1 of this series, a wave of what has become known as “long COVID” is emerging in many people who have recovered from the acute disease. A recent review chronicling the effects of long COVID reported that “long haulers” commonly experience fatigue, sleep problems, and joint and muscle pain long after their bodies cleared the virus. Other symptoms range from the mundane to the bizarre: brain fog, shortness of breath, fatigue, tremors, tooth loss, racing heart, glaucoma, and diabetes among others. Long haulers are also at a significantly increased risk of dying months after infection. A large study found that after surviving acute COVID-19, patients had a 59% increased risk of dying within six months after their initial diagnosis. This translates into an extra eight deaths per 1000 patients. Thus, the consequences of the acute disease itself are just the tip of the iceberg.

Because the official definition of the chronic problem is fluid, we are still learning what this new malady is. A UK study published last December simply defined the syndrome as a collection of symptoms lasting for more than 28 days after initial diagnosis. However, another British study as well as Britain’s National Institute for Health and Care Excellence vaguely and broadly define long COVID as “signs and symptoms that develop during or after an infection consistent with COVID-19, and that continue for more than 12 weeks and are not explained by an alternative diagnosis”. It does not specify a list of what the symptoms are.

But, there are many. A global survey tallied 205 different symptoms across 10 different organ systems that can persist after COVID infection has cleared, including those affecting the heart, lungs, gastrointestinal system, muscles, and joints. There also are frequent neurological and neuropsychiatric symptoms as highlighted in Part 1 of this series. A sufferer typically has several of these problems at a time (14 different symptoms on average), with the most debilitating usually being one of three: severe breathlessness, fatigue, or “brain fog”. Other common symptoms included compromised function of the lungs, heart, and kidneys sometimes requiring transplantation. There also have been skin rashes, and newly diagnosed diabetes.

What exactly is long COVID? About the only thing we can say with any certitude at this time is that long COVID exists but is not easy to describe, possibly because it really is more than one malady. The only constant between different long COVID patients with different symptoms is that the conditions are a collection of varied symptoms that persist long after the acute disease subsides, which sounds as vague as the British definitions described above. Long COVID clearly represents a new health malady or maladies since it is not generally found in uninfected people, but is common in COVID survivors; yet not all COVID patients experience it. Long COVID can affect any post-COVID patient at any age, but it mostly presents in middle-aged people and seems to slightly prefer women. Even people with asymptomatic CoV-2 infection can have late arising effects that fit the profile of long COVID.  Multiple studies have shown that infected people who do not get acutely ill can still show irregular lung scans, for example. One such study found that nearly 60% of people with asymptomatic infection showed some lung inflammation in CT scans. Other studies have shown that young people with asymptomatic or mild infections can have long lasting cardiac issues, while others show signs of small blood vessel damage.

Some of these symptoms can be similar to other recognized, if not fully understood chronic problems, such as chronic fatigue syndrome (CFS), which is one of the most common complaints that long haulers have. CFS remains a mystery malady with an unknown cause, but it often follows a viral or bacterial infection. It is, therefore, possible that long-COVID CFS-like problems might be no different from classic CFS. It also is possible that CFS-like long COVID symptoms are not at all related to what is recognized as classic CFS, and they are simply different illnesses with similar symptoms. Time and research will tell.

Broadly speaking, there are three types of long COVID patients, according to one NIH scientist. The first are generally characterized by “exercise intolerance”, meaning they feel out of breath and exhausted from even mild physical activity. The second are characterized by cognitive complaints like brain fog and/or memory problems. The third type experiences problems with the autonomic nervous system, which controls things like heartbeat, breathing and digestion. Patients in this group suffer from symptoms such as heart palpitations and dizziness. Impairments of the autonomic nervous system are known as dysautonomia, which is an umbrella term for a variety of syndromes. Physicians treating long-COVID patients say there has been a marked increase in dysautonomia since the pandemic began. A rehabilitation doctor at Mount Sinai Hospital, in New York, says that roughly 80% of people who show up at his long COVID clinic have dysautonomia of one type or another.

Not only do long COVID patients suffer chronic debilitation, they also are at increased risk of dying. One of the largest studies of Covid-19 “long haulers” found that COVID survivors had a 59% increased risk of dying within six months after contracting the SARS-CoV-2 virus. The excess mortality translates into about 8 extra deaths per 1,000 patients. Thus, the pandemic’s hidden toll is that many patients require readmission, and some die, weeks after the viral infection abates.

What causes long COVID? What causes the myriad of symptoms lumped under the long COVID umbrella are being studied, but it seems that not all are actually caused by the CoV-2 virus. Based on what we have gleaned from observations of a few million long COVID patients around the world, the focus is on three possible biological explanations. One is that long COVID is due to a persistent viral infection. A second possible cause could be an autoimmune disorder. The third possibility is that it is a lingering consequence of tissue damage caused by inflammation during the initial, acute infection.

Supporting the first hypothesis that the infection persists even after COVID disease has passed is that some patients very slowly clear the virus completely. The virus or its remnants persist along with the long lasting symptoms. These patients are not infectious so it could be that they harbor some altered form or fragment of the bug which does not replicate, but is nevertheless making some viral product that their bodies are responding to. This is known to occur with other viruses, including measles, dengue and Ebola. RNA viruses are particularly prone to this phenomenon, and CoV-2 is an RNA virus. Direct proof of this hypothesis is lacking, but pertinent clues abound. A study published recently in Nature showed that some people had traces of CoV-2 proteins in their intestines four months after they had recovered from acute COVID-19. Viral products from CoV-2 have also been found in people’s urine several months after their recovery. All this is circumstantial evidence, to be sure, but viral persistence is consistent with long COVID in certain patients.

The second hypothesis, that long COVID is an autoimmune disease, holds that the virus causes something to go awry with the immune system inciting it to attack some of the body’s own tissues. Some evidence backs this idea, too. The immune system is a complex, tightly regulated machine designed to discriminate between your own cells and foreign entities such as viruses. Sometimes this ability to distinguish self from non-self fails and an immune response is generated to one’s own tissues. Some patients suffering from long COVID have badly behaving macrophages, which are immune cells responsible for gobbling up foreign invaders and displaying them to immune cells inciting them to make antibodies or to kill infected cells. Other long COVID patients exhibit abnormal activation of their B-cells, which churn out antibodies against the pathogen that can sometimes cross-react with the body’s own cells causing complications. Since antibodies circulate for several months after an infection, it makes sense that this could cause problems months after recovery from the disease. Again, this evidence is circumstantial, but consistent with the observations in some long haulers.

The third hypothesis about the cause of long COVID holds that the body’s inflammatory response during the acute illness causes long-term damage to cells and tissues leading to chronic inflammation. This sometimes happens with other viral diseases, but it could be particularly likely with COVID-19 since out-of-control inflammation, caused by a cytokine “storm” is a common hallmark of severe cases of acute illness. One guess is that the inflammation damages parts of the autonomic nervous system, or that the virus might damage the cells that line blood vessels, either by infecting them directly and/or via inflammation from the immune response. This could change the way blood flows to the brain and other organs, and may thus explain the brain fog and other organ failure that is sometimes seen. This too remains circumstantial, but consistent with current observations in certain patients.

Bottom line: Long COVID probably embraces several different chronic conditions with different causes. Studies to investigate each of these possibilities are under way.

We will see.