What if covid-19 becomes a chronic disease

27 August 2020 13:25

Symptoms started in March, says Laura, a British girl of about 25. At first it just seemed like a bad flu: dry cough, fever, shortness of breath, loss of smell, “horrible nausea” and general fatigue. After three weeks of rest, things began to improve. But five months later, she still hasn’t recovered. Sometimes his symptoms subside for a week or two, but they inevitably return. “When it goes wrong, I can’t even make business calls, because if I talk too much I can’t breathe.”

In March, when covid-19 cases began to grow exponentially in one country after another, doctors focused on saving patients’ lives. Rapid knowledge sharing, clinical studies and practical experience have made the disease less deadly.

In the UK, around half of the patients admitted to intensive care units have died until mid-April. At the end of June, mortality was below 30 percent. Reductions have been observed in all age groups, which means that the decline cannot be due to the fact that fewer frail elderly have arrived in hospital. In places where the epidemic has slowed, quieter wards meant more attentive care, but the reason for the improvement was probably better knowledge of treatment options.

Shift the focus on who survives
Doctors have learned a lot. They immediately stopped attaching covid-19 patients to ventilators, which can cause lung damage. Oxygen delivered through cannulas inserted into the nostrils is much less invasive and often works the same. In British ICUs, the percentage of intubated covid-19 patients dropped from 90 percent in the first few days to 30 percent in June. Treatment protocols are further improved with the addition of dexamethasone, an immunosuppressive drug that increases the survival rate of patients in need of oxygen.

But now doctors and scientists are shifting the focus to patients who survive the infection, including the subset of people like Laura, who have never been sick enough to be hospitalized but never recovered enough to return to life. normal.

In most cases, covid-19 is a mild and short-lived disease. One third to half of the infected do not notice any symptoms. In those who get sick, symptoms usually go away within two to three weeks with home rest alone. In Europe, only about 3-4 percent of the infected are hospitalized.

At the same time, however, it is becoming clear that a small but significant percentage of infected people have symptoms that persist for months. Prolonged hospitalization is not unusual for patients hospitalized for pneumonia, a frequent complication of covid-19. It is also common for people who have been admitted to the ICU, and are therefore by definition seriously ill. But many doctors say the percentage of covid-19 patients with persistent problems is far higher than that seen with other viral diseases such as the flu. The problems are also more varied and often include pulmonary, cardiac and psychological symptoms, says Sally Singh of the University of Leicester, who coordinates the implementation of a post-Covid-19 rehabilitation program for the British Health Service.

Persistent effects
Cases of long-lasting symptoms have been reported since the early days of the pandemic. But with more than 22 million confirmed cases worldwide, and with infection rates peaking several months ago in most rich countries, statistical patterns of the virus’s persistent effects are beginning to emerge. An article in the British Medical Journal on August 11 concludes that 60,000 people in the United Kingdom report long-term symptoms. Yet so far only around 6 per cent of the British population – roughly four million people – appear to have been infected with the virus.

One hypothesis is that the immune system cannot stop itself after being called to fight an infection

The severity of the disease is one of the predictors of lasting problems. Ian Hall, who heads the University of Nottingham Biomedical Research Center, estimates that 30-50 percent of patients admitted to hospital with covid-19 still have significant symptoms even six to eight weeks after being discharged. This percentage increases further in the case of patients admitted to intensive care. But even those who got away with a milder disease, like Laura, are at risk. According to a study based on monitoring mainly US and UK patients, more than 10 percent continue to be ill for more than three weeks. They complain of fatigue, difficulty breathing, muscle aches and cognitive problems that many describe as “brain fog”.

Some long-term covid-19 patients may have suffered from undiagnosed underlying conditions such as diabetes or thyroid dysfunction, which have been “exposed” by the infection, says Avindra Nath of the US National Institutes of Health. According to others, the symptom set is similar to that seen in chronic fatigue or fatigue syndrome (CFS). The biological causes of CFS are still poorly understood, but US data indicate that in three quarters of cases it develops as a result of viral or bacterial infections.

One hypothesis is that the syndrome is caused by the fact that, after being called to fight an infection, the immune system cannot stop. It may be that Sars-cov2, the virus that causes covid-19, is more likely than others to cause such prolonged overreaction.

Lungs, heart and nervous system
While the root cause isn’t known, the growing understanding of what covid-19 is capable of doing to the human body can at least suggest what kind of care someone who takes a long time to heal might need. The hallmark of many cases of covid-19 is lung damage. The aggressiveness of the inflammation causes the destruction of lung tissue and the formation of scars. The scarring, in turn, prevents the passage of oxygen from the lungs to the blood. This can cause breathlessness even after light exercise.

Small studies conducted on covid-19 patients discharged from hospitals found that oxygen flow is impaired in 25-30 percent of cases. The prognosis is unclear. People admitted to ICU for other viral infections usually recover about 80 percent of their previous lung function fairly quickly, but the last 20 percent can take three to six months, says Dr. Hall. And in some cases, lung scarring can worsen over time, especially when associated with new health problems later in life.

Respiratory problems can also stem from another effect of covid-19: its tendency to cause blood clots, which is unusual for a respiratory virus. When formed in the lungs, clots can obstruct blood flow, making oxygen absorption even more difficult. And the virus can also cause shortness of breath indirectly by damaging the lining of blood vessels, thereby limiting the amount of blood that can flow through them.

Covid-19 can also damage the heart, inflaming the tissues that surround it and the blood vessels that carry nutrients to that organ. This can weaken the muscle and eventually lead to heart failure. Blood clots are also involved in this case, because the heart has to pump harder to push blood through the partially occluded vessels, so it weakens over time.

Faced with a bewildering array of symptoms and few precise explanations of their causes, doctors are desperate for guidance.

Nobody knows exactly how often this type of heart complication occurs. But the news from Germany is worrying, says Clyde Yancy, a cardiologist at Northwestern University in Illinois. Using MRI, a study showed that covid-19 causes inflammation and other changes in the heart, even in people who had tested positive for the virus more than two months earlier and had no symptoms at the time of the MRI. The changes were minimal and insufficient on their own to cause clinical symptoms. But even mild heart damage, if it persists long enough, can lead to heart failure, says Dr. Yancy.

The least understood are the long-term effects of covid-19 on the nervous system and brain. Patients with persistent post-covid symptoms complain of headaches, tingling and numbness in the feet and other neurological disorders. Problems that suggest autonomic nervous system malfunction, such as an irregular heartbeat, dry mouth, and gastrointestinal upset, are also quite common, Dr. Nath says. But the exact cause of these symptoms remains unclear, such as why more than half of infected people experience a temporary loss of smell (in some, rather than disappearing, the sense of smell is altered: after infection, things have a different smell than before).

Rehabilitation programs
Faced with a bewildering array of symptoms and few precise explanations of their causes, doctors are desperate for guidance. In the UK, one third of primary care physicians already have patients with prolonged post-covid symptoms. For now, the best thing they can do is initiate them into pulmonary or cardiac rehabilitation, which can improve a patient’s quality of life with something as simple as a breathing exercise. The UK, Belgium and other countries are studying rehabilitation programs for those who are recovering from covid-19. The waiting lists are already long.

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Lacking greater understanding, doctors must turn to what they have learned from other diseases. Persistent symptoms are not the sole prerogative of covid-19. Sometimes, complete recovery from other viral diseases such as the flu can take months. Data on chronic fatigue syndrome suggests that the chances of recovery are better in the first three months. More specific data is on the way. Thousands of patients have been enrolled in ongoing studies in the US, UK, Europe and China and are expected to begin reporting first results in the coming months. For now, those suffering from the prolonged effects of the disease need to worry not only about the physical symptoms, but also how long it will take to heal.

(Translation by Bruna Tortorella)

This article appeared in the British weekly The Economist.

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