- Researchers have identified a group of symptoms that persist in Covid-19 patients.
- This is due to patients' immune systems still interacting with the disease, even 10 weeks later.
- Some of these include flu-like symptoms, lung problems, and joint and muscle pain.
Seven "forms of disease", or groups of symptoms, have been found in patients with mild Covid-19, the disease caused by the new coronavirus, leaving them with significant changes to their immune system (even after 10 weeks), a new study by the Medical University of Vienna has found.
The study, published in the journal Allergy, involved 109 convalescents (patients recovering from Covid-19) and 98 healthy individuals in the control group.
"Several studies have investigated cellular immune responses in Covid-19 patients during disease but little is known regarding a possible protracted impact of Covid-19 on the adaptive and innate immune system in Covid-19-convalescent patients," the authors wrote.
The seven groups of symptoms
Various symptoms related to Covid-19 occurred in symptom groups, the researchers found. The seven groups of symptoms identified included the following:
- Flu-like symptoms (with fever, chills, fatigue and cough)
- Common cold-like symptoms (with rhinitis, sneezing, dry throat and nasal congestion)
- Joint and muscle pain
- Eye and mucosal inflammation
- Lung problems (with pneumonia and shortness of breath)
- Gastrointestinal problems (including diarrhoea, nausea and headache)
- Loss of sense of smell and taste and other symptoms
"In the latter group, we found that loss of smell and taste predominantly affects individuals with a 'young immune system', measured by the number of immune cells (T lymphocytes) that have recently emigrated from the thymus gland," lead author and immunologist Winfried Pickl, from the Centre for Pathophysiology, Infectiology and Immunology at MedUni Vienna, explained in a statement.
"This means that we were able to clearly distinguish systemic (e.g. groups 1 and 3) from organ-specific forms (e.g. groups 6 and 7) of primary Covid-19 disease," Pickl said.
'Immune system still engaged with disease weeks later'
Additional findings by the team include Covid-19 leaving behind long-lasting detectable changes in the blood of convalescents, which they describe as being similar to a fingerprint.
To explain this, they commented that the number of granulocytes (a type of white blood cell which is otherwise responsible in the immune system for fighting bacterial pathogens) were found to be significantly lower than normal in the Covid-19 group.
"However, both the CD4 and CD8 T cell compartment developed memory cells and CD8 T cells remained strongly activated," Pickl said.
"This indicates that the immune system is still intensively engaged with the disease several weeks after initial infection. At the same time, the regulatory cells are greatly diminished – and that is likely a dangerous mix, which could lead to autoimmunity," he added.
Latest findings can lead to better understanding of Covid-19
The team also detected increased levels of antibody-producing immune cells in the blood of convalescents. The higher the fever of the affected patient during the mild course of the disease, the higher the antibody levels against SARS-CoV-2, they found.
"Our findings contribute to a better understanding of the disease and help us in the development of potential vaccines, since we now have access to promising biomarkers and can perform even better monitoring," the team said.
"Above all, the study shows that the human immune system 'doubles up' when defending against Covid-19 with the combined action of immune cells and antibodies… and that the cells are also able to memorise certain 'moves' on the part of the virus… and respond to them."
The researchers believe their findings could be used towards the development of highly-effective Covid-19 vaccines.
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