An infection with the Sars-CoV-2 coronavirus can cause a large number of apparently completely different symptoms. But, as it now shows, there is a certain order behind this: the researchers found that with the mild course of Covid-19, certain groups of symptoms often occur together. Using these clusters, they identify seven different forms of the disease. Blood tests from convalescents also revealed that even ten weeks after a coronavirus infection, there are still significant changes in the immune system.
Cough, fever and flu-like symptoms – these symptoms are often the main symptoms of a coronavirus infection. However, during the pandemic, it has been shown that Sars-CoV-2 can attack a large number of organs and tissues in our body and cause a wide range of symptoms. Some patients suffer from headaches and neurological failures, others develop an increasing lack of oxygen or develop abdominal pain and diarrhea. Nonspecific muscle pain and fatigue are common symptoms of Covid-19. In more severe cases, pneumonia and inflammatory reactions occur throughout the system. The long-term effects of the infection have also been scarcely investigated. It is becoming evident that a considerable number of patients still have symptoms weeks to months after the acute phase of the disease or even develop them only then.
Seven different symptom complexes
Bernhard Kratzer of the Medical University of Vienna and his colleagues have now investigated what is behind these courses immunologically and whether there is possibly a system for the very different symptoms of Covid-19. “Although several studies have examined the cellular immune responses of patients with Covid-19 during their acute illness, so far we know little about the long-term effects that Covid-19 has on the adaptive and innate immune systems of convalescents,” they explain. For the study, they analyzed the blood of 109 Covid-19 convalescents whose infection with Sars-CoV-2 occurred about ten weeks ago. They determined which immune cells and antibodies were present in the blood samples and asked all participants in detail what symptoms had occurred during acute Covid’s disease 19. All convalescents at that time had a very moderate course at Covid-19.
The evaluation of the symptom reports showed that, with the Covid-19 mild course, there are apparently certain groups of symptoms, often combined. “We were able to clearly differentiate between systemic and specific forms of organs from primary Covid-19 disease,” reports senior author Winfried Pickl of Medical University of Vienna. From these combinations, he and his team concluded that there are seven different forms of the disease with a mild course of Covid-19. Knowledge of these variants of the disease may, in the future, help to identify possible infections more quickly and possibly also treat them more specifically. The first form is characterized by classic flu-like symptoms – fever, exhaustion and cough. In its second variant, the infection is more like a typical cold with runny nose, sneezing, dry throat and nasal congestion.
Covid-19’s third form, on the other hand, manifests itself only or predominantly through joint and muscle pain, a fourth through pronounced inflammation of the eyes and mucosa, as scientists report. A fifth symptom complex is lung problems with pneumonia and shortness of breath. In the sixth form, those affected suffer mainly from gastrointestinal problems with diarrhea, nausea and headache. Finally, the seventh form of the disease is the loss of smell and taste. “In the latter group, we were able to determine that more people with a ‘young immune system’, as measured by the number of T lymphocytes that recently migrated from the thymus, are affected by loss of smell and taste,” explains Pickl.
Long-term immunological changes
Regardless of the variant of Covid’s acute disease 19, there are many similarities in terms of long-term immunological consequences. Thus, Sars-CoV-2 leaves a kind of immunological fingerprint on the immune system and in the blood of convalescents. The number of white blood cells, which are otherwise responsible for fighting bacterial pathogens in the immune system, is significantly less than normal in Covid’s convalescents. There are more memory cells for this and the cytotoxic CD8 + T cells remain strongly activated. One of its tasks is to kill virus-infected cells. “At the same time, regulatory cells are very small – this is a dangerous mixture that can also lead to autoimmunity,” explains Pickl. Antibody-producing immune cells were also increasingly present in the convalescent’s blood – the stronger the affected person’s fever, the higher the levels of antibodies against the virus.
“It shows that the immune system is still dealing intensely with the disease many weeks after the first infection,” says Pickl. The new findings help to better understand Covid’s disease and its consequences. “They also help us in the development of possible vaccines, as we can now use promising biomarkers and do even better monitoring,” explain the scientists. It is now a matter of implementing these findings and using them for vaccine development.
Source: Bernhard Kratzer (Medical University of Vienna) et al., Allergy, doi.org/10.1111/all.14647