1. Introduction

The COVID-19 pandemic has confronted healthcare professionals with the task of early diagnosis and provision of medical care to patients with a new coronavirus infection. Scientific work is being carried out to study the clinical and epidemiological features of the disease, and to develop new means of its prevention and treatment. The potential possibility of replenishing certain microelements in patients with COVID-19 with the aim of early recovery of patients is being discussed [1,2,3].

Systemic complications caused by the COVID-19 virus pose a serious threat to the health of children, requiring comprehensive and effective treatment. In recent years, much attention has been paid to the role of microelements in maintaining immunity and fighting infections. Despite this, the effect of microelements on the course of COVID-19 in children has not been sufficiently studied. The relevance of this study on the role of microelements in the treatment of children with COVID-19 is due to the need for a deeper understanding of the influence of microelements on the immune system of the child’s body in the context of this disease. Given the characteristics of the child's body and its response to exposure to the SARS-CoV-2 virus, elucidating the role of specific micronutrients can provide valuable information to optimize treatment strategies and maintain the health of children during the pandemic. This approach can facilitate the development of individualized therapeutic regimens, improving treatment outcomes and reducing the negative consequences of the disease in children. The most informative way to determine macro- and microelements in the body of children, in comparison with other biological media, is the study of hair, since hair occupies the second place in the metabolic tissue of the body. In recent years, hair examination has been increasingly used as one of the methods for identifying metabolic disorders [5,6,7], because The physiological balance of chemical elements in the human body is a prerequisite for ensuring normal functioning and maintaining health. Carrying out multi-element hair analysis makes it possible with a high degree of reliability to identify risk groups for hypo- and hyperelementosis, to develop and promptly apply preventive measures that restore disturbances in the homeostasis of elements, as well as the associated biochemical and physiological functions of the body [9,10,11]. In addition, according to the analysis of the content of the microelement composition of hair, it may be sufficient to judge the content of the above microelements in the blood, which is, from a practical point of view, a more comfortable definition in children. It can also be assumed that a decrease in the degree of general mineralization of hair is an indicator of rapid exhaustion, a low level of functional reserves of the body, and its increase in relation to the average indicators reflects the tension of compensatory and adaptive mechanisms.

The aim: The study aims to analyze the concentration of trace elements such as zinc, calcium and phosphorus in abrasive samples of the nasal and oropharyngeal mucosa of children who have had COVID-19.

2. Material and Methods

In the present study, 112 children under the age of 15 years who had a confirmed diagnosis of coronavirus infection (COVID-19) were examined and, for comparison, 50 practically healthy children who made up the control group. Sick children consisted of 3 groups depending on age: 1st group - 52 children aged 1 to 6 years, 2nd group - 28 children aged 6 to 12 years and 3rd group - 32 children aged from 12 to 15 years old.

The diagnosis of COVID-19 was established by detecting SARS-CoV-2 RNA using the polymerase chain reaction (PCR) method on samples taken from the nasopharynx and oropharynx.

As part of the laboratory studies, thorough analyzes were carried out, including determination of a general blood count, biochemical parameters, as well as the study of microelement composition in the hair of children. The general blood analysis included the study of hematological parameters, including leukocyte count, red blood cells, hemoglobin and platelets.

Biochemical studies are aimed at determining the levels of various biochemical markers that highlight the state of the body in the context of COVID-19 infection. In parallel, microelement composition in hair was analyzed, providing a deeper understanding of the influence of microelements on the disease. Hair samples were collected in the following order. We put on a new pair of rubber gloves, not treated with talcum powder; remove the comb, scissors and hair clips from the isopropyl alcohol solution, lay them out on a disposable napkin and dry them; using clamps, a section of hair was isolated, the boundaries of which run between the upper tips of the ears and the back of the neck; Using surgical stainless steel scissors, 10–20 basal strands of hair were cut in 5–10 different areas of the occipital region, 3–5 cm long. The cut hair was placed in a clean sealed plastic bag with a fastener, a label with the sample marking was pasted, and thus the samples were stored and transported. Selected hairs were washed to remove surface contamination. The hair sample was placed in a glass, filled with acetone and kept for 10 minutes with periodic stirring. Then the hair was washed three times with distilled water and the soaking in acetone was repeated for 10 minutes. Washed hair is placed between sheets of filter paper and dried at a temperature of 20-23°C. The control group consisted of 18 children who were in apparently healthy condition, providing a baseline for comparison of changes caused by COVID-19.

3. Results and Discussion

As a result of the study, it was revealed that among the children examined, slightly more than half (53.8%) were structured and lived in urban areas. 69% of them had a pronounced predisposition to frequent diseases. The symptoms of COVID-19 in these children manifested a clinical appearance similar to acute respiratory viral infections (ARVI), including a dry cough, sore throat, runny nose, and a temperature rising to 38°.

Additional symptoms included rash in 11.5%, inflammation of the mucous membrane of the eyes in 7.7%, headaches in 9.6%, and signs of gastrointestinal distress in 11.5% of children. The duration of the COVID-19 disease averaged 7-10 days. After 2 months from the onset of the disease, the health status of these children was re-examined.

Hair examination revealed a significantly lower level of calcium in the hair of children of the younger group - 795.0 ± 211.72 mcg/g, and in the control group - 1185.33 ± 255.84 mcg/g, which may indicate insufficient absorption or increased losses.

In children of the 2nd group, a similar picture was revealed - 95.2 ± 2.76 μg/g, and in the control group - 104.5 ± 3.2 μg/g, p<0.05. And in the group of adolescents, these figures were 678.0±15.7 mcg/g versus the value of healthy children – 795.0±21.1 mcg/g, p<0.05. It is known that a reduced calcium content in children’s hair correlates with the development of diseases of the endocrine system and skin diseases, as well as blood diseases. Calcium, which has numerous metabolic properties (activator of enzyme systems, participant in the cascade of reactions of glycogenolysis, gluconeogenesis, lipolysis, etc.), has a pronounced effect on the state of the nervous, musculoskeletal, gastrointestinal, cardiovascular, hematopoietic and endocrine systems. This macronutrient also affects immune status, cognitive function and allergic inflammation. A striking example of a pronounced calcium deficiency is a whole group of pathological conditions resulting from its deficiency (osteoporosis, osteopenia, rickets), as well as other clinical situations.

With zinc deficiency, not only T-cell immunity, phagocytic activity of leukocytes, the content of lysozyme, and complement are reduced, but also protein and RNA synthesis is significantly reduced, and as a result, growth and development are delayed. In our study, we found that zinc deficiency was detected both in the blood and in the hair - and in the hair it was more pronounced. Thus, in the main group A of children, zinc in the hair contained an average of 175.63 ± 20.52 μg/g, and in healthy children - 242.33 ± 27.32 μg/g, the difference of which is 25%, p<0.05. The average values of zinc content in the hair of children of the main group were in the range of the arithmetic mean and corresponded to the lower limit of the reference values typical for persons of this age. In the main group B, these figures were 186.22±18.28 mcg/g, and in healthy children - 197.78±27.32 mcg/g; in children of group 1 we observed a similar picture - 150.34± 19.26 mcg/g, and in healthy children - 175.63±20.52 mcg/g, p<0.05.

Zinc deficiency of varying severity was found in 26.3% of children in the main group. At the same time, pronounced deficits of grade 3 - 4 were observed almost 2 times more often in children of the 2nd group.

It is interesting to note that the number of frequently and long-term ill children in the main group is 35.1%. We believe that it was precisely the insufficient supply of essential microelements of the body's antioxidant and immune (zinc) defense that led to a significant increase in the proportion of frequently and long-term ill children in the main group.

Analysis of the level of microelements (zinc, calcium and phosphorus) showed that the calcium level in patients in the early recovery period averaged 1.9±0.04 mmol/l, which is significantly lower than in children in the control group (2.2±0.05 mmol/l, P<0.01). The level of zinc in children who recovered from COVID-19 during this period was on average 9.5±1.0 mmol/l, which is 1.5 times lower than in the control group (P<0.01). Similarly, the phosphorus level in patients averaged 1.18±0.02 mmol/L, which was also statistically significantly different from the control values (1.27±0.01 mmol/L), (P<0.01).

Study findings indicate significant changes in micronutrient levels (calcium, zinc and phosphorus) in children following COVID-19. A decrease in the level of calcium, zinc and phosphorus was found, which emphasizes the need for additional attention to microelement status in the process of treatment and rehabilitation. These results support an individualized approach to care for children after illness to ensure full recovery and minimize potential consequences.

4. Conclusions

This study is consistent with previous data and shows an association of micronutrient deficiencies and adverse outcomes in COVID-19. Because the relationship between a well-functioning immune system and adequate levels of micronutrients has been well documented, further research is needed to evaluate the benefits of micronutrient supplementation for both the prevention and treatment of COVID-19.