Covid-19 infection is not limited to the respiratory tract. Practical studies show that a significant number of patients are affected by the virus in the nervous system. The mechanism of its effect on nerve cells has not yet been studied, but scientists do not doubt that there is a connection: temporary loss of taste or smell has been recognized as a specific symptom of Covid-19 since mid-March. In addition, the virus is capable of entering the brain directly through the nasal passages, which in turn can cause a whole range of complications and disrupt the normal functioning of almost any organ. The list of possible associated diseases is long: from digestive problems and clogged blood vessels to heart failure and encephalitis.
Four months into the epidemic, scientists still know very little about the SARS-CoV-2 virus and its effects on the human body. The full picture of the infection is slowly emerging from hundreds of articles in scientific journals, as doctors from around the world share their experiences treating coronavirus patients. As a result, the list of possible symptoms of Covid-19 continues to grow (there are already more than a dozen), as does our understanding of what other organs the virus can affect and what complications the disease can cause in addition to pneumonia.
We explain quickly, simply, and clearly what happened, why it matters, and what happens next. Episodes End of story: Podcast Advertising. Most commonly, doctors describe disorders of the nervous system. Two studies conducted in France and China have concluded that more than one-third of those infected experience some form of neurological symptoms. Overall, however, the new infection is characterized by a much more diverse and even individualized approach. The list of described complications of Covid-19 that physicians have encountered in practice includes gastrointestinal disorders, heart problems, and blood clotting disorders. But the virus can affect the nervous system in many different ways – it’s not just a temporary loss of feeling. In particular, several cases of encephalitis (inflammation of the brain) and Guillain-Barré syndrome have been described as side effects of Covid-19: the patient’s immune system begins to attack its own nerve cells, leading to muscle weakness and, in severe cases, paralysis. American doctors are alarmed by reports that in just two weeks in New York, five cases of severe stroke were recorded in coronavirus patients – and this happened in relatively young people (under 50 years of age) without other obvious symptoms of Covid-19. According to preliminary data, the coronavirus caused them to develop blood clots in large blood vessels as a side effect, which eventually led to an acute disruption of cerebral blood flow. However, neurological disorders are mainly observed in severe patients. In such cases, these symptoms sometimes persist even after the patient has recovered from Covid-19.
The virus can disrupt the functioning of the nervous system both indirectly, through excessive activation of the immune system (known as a cytokine storm), and directly. This has been shown in autopsies of people who have died from Covid-19. Viral particles have been found in the victims, including in the brain. One theory is that the infection travels from the respiratory tract to the brain through olfactory receptors in the nose. This is not a unique ability of the new coronavirus. Some other viruses, including influenza and measles, can also cause brain infections, sometimes leading to neurological disease, although this is quite rare. With Covid-19, however, the situation is a bit more complicated. First, the number of people infected is already over 3 million, which means that even in rare cases, there are still quite a few cases. Second, once the virus reaches the brain, further infection is almost inevitable: the surface of brain cells contains the same membrane receptor, ACE2, through which the virus easily penetrates the inside and causes inflammation. The same receptor is also found on the cells that line the inner surface of blood vessels – which is why, in severe cases, the virus breaks through from the respiratory organs into the general bloodstream. As a result, thrombotic complications occur in nearly one in three patients with coronavirus pneumonia. Through the blood, the virus can reach any organ, including the brain. However, according to the latest data, almost half of all infected people can carry Covid-19 without any symptoms. In an attempt to understand why some people have a disease that goes completely unnoticed while others suffer such severe consequences, several thousand pairs of identical twins were studied in Great Britain. Preliminary data suggest that the severity of the infection, many of its symptoms, and possibly the likelihood of infection are strongly influenced by genetic factors, or heredity.
