Post-covid syndrome was defined as the presence of symptoms and/or signs of damage to various organ systems that develop during or after a previous COVID-19 infection persist for more than 12 weeks and cannot be explained by an alternative diagnosis. (A Quick Guide to COVID-19: Managing the Long-term Effects of COVID-19 (NG188). Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) can be described as a disease of unknown etiology characterized by the presence of permanent fatigue that does not recover after the proper rest, accompanied by various somatic symptoms. Establishment of the diagnosis is based on the analysis of clinical manifestations, however, due to their diversity; it takes a lot of time and medical experience. The application of the statistical analysis may allow simplifying and unifying this task. At the same time, considering diverse manifestations of the CFS/ME, one may allude that there are several different clinical variations of this disease and, therefore, symptoms can be grouped into "clusters". In this paper a possible correlation was revealed between various clinical symptoms of CFS/ME, using the principal component analysis (PCA) associated with the correlation coefficients of the Pearson’s matrix. A hypothetical physical model of the correlation of immunological symptoms was created. In addition to the positive correlation expected for the symptoms of one disease, negative relationships were also revealed, which may represent some unknown pathophysiological processes of CFS/ME and requires further study. The identification of key symptoms in patients of this group can contribute to the introduction of new diagnostic criteria, which will lead to an improvement in the quality of life and medical care for these patients.