Symptoms, cytokine shock … What we know and what we don’t know about Covid-19

One of the challenges of a pandemic as rapid and widespread as that of the new coronavirus is that knowledge related to Covid-19 changes almost daily. They are often disseminated by hundreds of preliminary scientific publications that doctors in the field do not always have time to read, busy as they are saving lives.

Some experts wonder if researchers and scientists are not going too fast in their race, however well-intentioned, to understand the pandemic, causing more confusion than anything else.

Covid-19, this “unknown” disease with many faces

Drawing up a robot portrait of the SARS-CoV-2 coronavirus is not easy. But by combining the latest studies, the latest research, observations can be made.

  • Half of those infected do not develop symptoms, but are a vector of contagion
  • Most patients have only mild symptoms
  • In serious patients, it’s not the virus that kills, it’s an uncontrolled immune system reaction that can damage most vital organs, a phenomenon called cytokine shock
  • The cause of severe symptoms in some patients, regardless of age, remains unknown
  • The virus can attack the nervous system. In some cases, respiratory failure is linked to neurological failure, not pneumonia
  • It is not certain that the cured patients will stop being contagious
  • doubts remain as to the duration of immunity after illness

This constantly evolving information partly explains why we hear different, sometimes contradictory, opinions from the authorities, whether it is the need to wear a face mask or how to identify the first symptoms. .

Some still claim that “it is only a small flu” when it is proven that it is a real plague for public health.

At the beginning of the epidemic, political, health or scientific authorities argued that cough and fever were the unequivocal symptoms of a possible contraction of Covid-19. Today, it is proven that the disease can cause a wide variety of symptoms or even a complete absence of symptoms. It is now estimated that around 50% of infected patients are asymptomatic – which has been one of the main factors in the rapid spread of the new coronavirus.

Many specific details about the disease remain almost unknown. Doctors have learned to fight Covid-19 almost on a case-by-case basis, although protocols are now improving.

Euronews spoke with doctors working on the front line to better understand the disease. And thanks to their expertise, try to understand why this disease represents such a danger for populations at risk, as well as for our health systems.

How does Covid-19 infection work?

Roger Paredes, head of the infectious diseases department at the Germans Trias i Pujol hospital, near Barcelona, ​​explains that there are three different stages of infection for people who develop symptoms of Covid-19:

  • The viral phase : when the virus replicates very quickly in the respiratory system. Symptoms are similar to those of regular flu and go away on their own after about 6-10 days. This is the case for around 80% of patients.
  • The pulmonary phase : the remaining 20% ​​of patients may develop pneumonia. It is a very specific type of pneumonia, which attacks both lungs and causes respiratory distress.
  • The severe phase : About 10% of patients develop cytokine shock, an uncontrolled inflammatory response of the immune system that is responsible for most critical conditions and, ultimately, deaths.

Who is the real killer?

Doctors in the field report that severe cases do not develop a high viral load (i.e. a concentration of virus) but rather cytokinic shock syndrome.

“Cytokine shock is a problem we quite often face in intensive care“says Rafael Máñez, head of the intensive care unit at Bellvitge Hospital, also near Barcelona. Other infections and even certain medicines can trigger it.”The problem is that we have no treatment, neither for the virus nor for the inflammatory response“, explains the doctor to Euronews.”We only have supportive treatments, to protect the patient’s vital organs“Doctors use respirators, or drugs to control blood pressure, or corticosteroids to reduce inflammation.

Another avenue is to use drugs to block Interlukin-6, a pro-inflammatory cytokine produced by the immune system.

According to him, cytokine shock occurs during the flu season, but the admission of patients is gradual. “Due to Covid-19’s exceptional infection rates, we are receiving more patients than we can manage“.

Dr. Máñez highlights a nuance in the consensus that it is better to have strong defenses to cope with the disease: “You don’t need a strong immune system, but a balanced system“, he advances.

Dr. Paredes is leading a clinical study in cooperation with the National Institute of Health in the United States using remdesivir. This study will last three years.

Cytokine shock, a little-known phenomenon

The exact mechanisms of these cytokine storms are virtually unknown“says Dr. Paredes.”The inflammatory reaction is a natural reaction of the immune system. It is necessary to repair damage to cells. In normal pneumonia, germs damage the lung tissue and the immune system generates an inflammatory reaction to stop it. What happens is that the immune system “kills” certain cells to repair damaged tissue. What is happening now with the coronavirus is that instead of sending a few cells, it sends tons of cells which generate an uncontrolled inflammatory response, not only in the lungs, but which can be generalized in the body of the patient“.

Indeed, cases of renal, intestinal or coronary lesions30116-8 / fulltext) have been reported. “I have a young patient who suffers from myocarditis (inflammation of the heart muscle, editor’s note)“, explains Dr. Máñez.

It seems that some patients with severe headaches may have encephalitis (inflammation of the brain).

The factors that predispose patients to develop this syndrome are unknown at this time. With regard to the Covid-19, age is very important. “The key is to understand who is most vulnerable“says Dr. Paredes.”About 70% of our patients are over 70 years old, and between 10 and 15% are under 60 years old“.

Scientists believe that genetics play a major role in the rare cases of young patients developing the syndrome.

When people suffer from cytokinic shock, degradation is very rapid, regardless of their age, and it is therefore very important to identify the first signs, explains Dr. Paredes.

According to Dr. Máñez, obesity can increase the risk of an inflammatory reaction.

Covid-19 can attack the central nervous system

Research and field observations show that the SARS-CoV-2 virus responsible for Covid-19 disease can attack the central nervous system. Dr. Paredes says that some patients in respiratory distress sometimes do not experience lack of oxygen or pneumonia.

He suspects that some patients are entering respiratory distress precisely because their nervous system is failing to function properly. This has also been reported in some preliminary research articles.

The commonly reported loss of smell and taste could also be linked to the central nervous system in some cases, according to Paredes.

Doctors around the world are reporting reports of neurological events suggesting that the virus may enter the central nervous system, such as blood clots, dizziness, confusion, or seizures. The University of Brescia hospital in Italy has opened a separate NeuroCovid unit to treat patients with neurological conditions related to the new coronavirus, according to the New York Times.

A team from Wuhan, the initial epicenter of the pandemic, published a preliminary research article reporting neurological disorders to different degrees in 36.4% of the 214 patients studied. The “predecessors“SARS-nCoV-2, SARS and MERS, could also make their way to the central nervous system.

All the studies suggest that these are rather rare cases, but that they should not be underestimated.

And after the illness?

Even as scientists gradually begin to gain a better understanding of the disease, many questions remain as to the prospects of the cured patients, such as the duration of their immunity or the long-term effects on their own organs.

According to Roger Paredes, patients recovered in Spain spend two more weeks in quarantine at home before being tested again. The duration during which these patients remain a vector of contagion for the others is currently debated. Current PCR tests are not 100% reliable to determine this. Antibody testing will be required in large population samples.

As many governments prepare their exit plans, the European Center for Disease Control (ECDC) has warned that rushing could lead to a resurgence of infections and that with the data we currently have available, no European country is ready to lift the restrictions on movement and social distancing due to the difficulties in controlling new cases.

Before considering the lifting of any measure, Member States will need to ensure that improved screening and surveillance systems for the population and hospitals are in place to inform and monitor escalation / de-escalation strategies and to assess epidemiological consequences“, specifies the ECDC.

It is interesting to note that despite scientific progress, staying at home, soap and hygiene have so far been the main obstacles to the virus. “We were not aware of it. We felt that with the knowledge we had, it couldn’t happen. With this crisis, we will realize that we are very vulnerable“, summarizes Dr. Rafael Máñez.


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