There are seven “forms of disease” in a mild coronavirus infection and the disease leaves behind dramatic changes in the immunity system, according to a study published in the journal Allergy.

The researchers of the study, a team of MedUni Vienna scientists, stated that this could play a significant role in the treatment of patients and in the development of a potential vaccine against the virus.

The research was led by immunologist Winfried F Pickl and allergologist Rudolf Valenta, both from the Centre for Pathophysiology, Infectiology, and Immunology.

Also read: Novel antibodies reduce Covid-19 viral load and severity, study finds

For the study, the researchers gathered 109 convalescents and 98 healthy individuals in the control group. The researchers were able to show that various symptoms related to Covid-19 occur in symptom groups.

They discovered seven groups of symptoms: 1) flu-like symptoms (with fever, chills, fatigue, and cough), 2) common cold-like symptoms (with rhinitis, sneezing, dry throat and nasal congestion), 3) joint and muscle pain, 4) eye and mucosal inflammation, 5) lung problems (with pneumonia and shortness of breath), 6) gastrointestinal problems (including diarrhea, nausea, and headache), and 7) loss of sense of smell and taste and other symptoms.

The researchers noted that the 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.

Pickl said: “This means that we were able to clearly distinguish systemically (e.g., groups 1 and 3) from organ-specific forms (e.g., groups 6 and 7) of primary Covid-19 disease.”

Covid-19 impression in the blood

The researchers also established that Covid-19 leaves behind long detectable changes in the blood of convalescents, very similar to a fingerprint.

Also read: Asymptomatic and mild Covid-19 cases may be infectious for 10 days or less: Study

Pickl explained in the study: “Both the CD4 and CD8 T cell ― important to induce immunity ― compartment developed memory cells and CD8 T cells remained strongly activated. This indicates that the immune system is still intensively engaged with the disease several weeks after the initial infection. At the same time, the regulatory cells are greatly diminished ― and that is likely a dangerous mix, which could lead to autoimmunity.”