The literature review is devoted to the chromosomally integrating viruses, the integration property. These are revealed using modern diagnostic methods, including highthroughput sequencing. The review describes various types of viruses, such as retroviruses, adenoviruses, herpes viruses, papillomaviruses, hepatitis B, SARS-CoV-2 and others. These viruses have the ability to integrate their genomes into the host cell genomes and their prevalence. Modern information on the molecular mechanisms of viral integration and methods of differential diagnostics is presented. Each of these viruses has its own unique ways of interacting with the host cell genome to maintain a latent state, which determines the specifics of the infectious process and pathological consequences for the body due to the possibility of effective reactivation.

Diagnosis of chronic Lyme disease is a challange for a clinician, even if there is modern laboratory and instrumental facilities at the hospital. Borreliosis is known for polysystemic and variable clinical picture. This article describes the clinical feachures and diagnosis of chronic borreliosis with central nervous system involvement. Various clinical variants of the disease and available methods of specific and nonspecific diagnosis are listed. The theoretical part of the work was carried out based on materials from 34 publications devoted to the problem of chronic neuroborreliosis. Also we describe the clinical case that illustrates the difficulties of managing this group of patients.

Viral hepatitis D (HDV infection) worsens the prognosis of HBV infection course in 80-90% of cases, accelerating fibrosis and leading to liver cirrhosis or hepatocellular carcinoma. Hepatitis D affects at least 125 000 people in Russia, and in the world, according to rough estimates, there are 15–20 million patients. The main measures to combat hepatitis D can be attributed to widespread scheduled vaccination against hepatitis B and the appointment of effective etiotropic therapy. A detailed study of the hepatitis D virus genome structure and its replication cycle allows the development of a number of drugs that target and block key mechanisms of the virus life cycle. This review provides a brief characterization of hepatitis D virus, its genome structure, key processes of its life cycle and mechanisms of genetic information realization. The review considers the main potential targets for targeted antiviral therapy of HDV infection and describes specific drugs (bulevirtide, lonafarnib, nucleic acid polymers). The review describes the mechanism of action of bulevirtide, which according to the current national clinical guidelines is a key element of antiviral therapy as monotherapy or in combination with pegylated interferons. Promising drugs affecting the processes of synthesis and post-translational modification of HDAg or reducing the production of surface proteins of hepatitis B virus are also considered. Further efforts are needed to develop safe, effective and cost-effective drugs against hepatitis D to ensure that treatment is widely available to those who desperately need it. Therefore, it is important that the life cycle of the hepatitis D virus be studied further, in greater detail, in order to develop highly effective antiviral drugs.

The presented review searched for articles in the databases PubMed, Web of Science, Scopus, Google Scholar, eLibrary (2002-2022) and assessed the immunogenicity of the 23-valent polysaccharide pneumococcal vaccine (PPV23) in adult patients with rheumatoid arthritis (RA), receiving various antirheumatic drugs. The results of this review indicated sufficient immunogenicity of PPV23 in RA patients receiving monotherapy with various biological drugs (bDMARDs) (TNFα inhibitors, IL6 receptor inhibitors, T-lymphocyte costimulation blockers), targeted synthetic disease-modifying antirheumatic drugs (tsDMARDs), and glucocorticoids (GC) in medium and low doses. Monotherapy with methotrexate (MTX), rituximab and combination therapy with bDMARDs +MTX, tsDMARDs+MTX in RA patients reduced the postvaccination pneumococcal response. IgG AT generated in response to PPV23 injection shown functional activity even in RA patients whose antibodies were either lowered in patients receiving MTX or were not detectable at protective values following bDMARD therapy. The potential for pneumococcus antibody production in RA patients receiving therapy with disease-modifying antirheumatic drugs (DMARDs), tsDMARDs and bDMARDs, was concluded. Vaccination against pneumococcal infection should be advised prior to starting therapy due to the likelihood of low antibody levels developing during rituximab treatment.

Aim: To study the manifestations of the COVID-19 epidemic and the clinical and epidemiological characteristics of adult patients with a new coronavirus infection during the dominance of the Delta SARS-COV-2 in the Russian Federation.

Materials and Methods: Study included patients aged ≥18 years with a laboratory-confirmed diagnosis of COVID-19, detected in the period from 09/01/2021 to 11/30/2021 (n= 2 619 298) in 85 Russian regions.

Results: There were 2 periods of rise and decline in the COVID-19 incidence and mortality during the spread of the Delta SARS-CoV-2 in Russia: June-September and OctoberDecember 2021 (Wald – Wolfowitz criterion, p<0,05). The median age of patients was 49 [36–63] years, 61,1% were women. Most of patients were 30–39 years old (21,0%), the lowest proportion was among 18–29 years old (12.1%) (p<0,05). Proportion of patients with mild disease was 75,4%, moderate – 18,8%, severe – 3,3%, extremely severe – 2,5% (p<0.05). Hospitalization rate was 23,7%, proportion of patients treated in the intensive care unit was 12.9%, and rate of invasive mechanical ventilation was 9,8%. The median period from the onset of symptoms to the diagnosis was 3 [1-6] days, the duration of the disease and hospitalization was 13,0 [10–16] and 12,0 [9–17] days, respectively. The median age of the deceased patients was 73 [65–82] years, of which 59,1% were women, 61,5% were persons ≥70 years old. The presence of one or more comorbidities was found in 73,9% of deceased patients (OR=17,1; 95% CI: 16,8–17,3).

Conclusion: during the period of the spread of the Delta SARS-COV-2 variant in Russia, the number of patients with severe and extremely severe disease among adult patients without taking into account the vaccine history was 5,8%. Old age and the presence of concomitant diseases were key risk factors for adverse outcomes of COVID-19.

The pandemic caused by the new coronavirus disease (COVID-19) was the largest in the last century since the Spanish Flu. One of the important strategies in the fight against COVID-19 has been vaccination. Although the end of the pandemic was declared in May 2023, the question of how the epidemic situation will spread (seasonal waves, new disease or gradual disappearance) remains unclear due to the high variability of the pathogen, which determines and changes recommendations in further immunization tactics.
Purpose of the study: to compare the clinical effectiveness of the first vaccination, as well as 1–3 revaccinations against a new coronavirus infection in people of different ages and health conditions.
Research methods: clinical observation of 1159 people aged 19 to 92 years (74,8% women), assessing the frequency and severity of confirmed coronavirus infection before vaccination and for 2 years after vaccination in comparison with health status and age of those vaccinated; laboratory examination – examination of a nasopharyngeal smear using realtime PCR (Real-time PCR) for SARS-CoV-2; statistical data processing.
Results: out of 1159 people, 255 people (22.0%) fell ill before vaccinations, of which 154 people (22.5%) were among 684 healthy people, and 101 out of 475 (21.2%) were among people with chronic pathology. It was found that before the introduction of vaccinations, people 40–59 years old were significantly more likely to get sick compared to the group 60 years old and older (30,4% and 18,3%, respectively, p=0,015). Since December 11, 2020, 1106 out of 1159 people have been vaccinated against the new coronavirus infection, of which with adenovector vaccines (1056 people) and based on other technological platforms (50 people). Revaccinations were carried out only with adenovector vaccine: 1 revaccination – 780, 2 revaccination – 249 and 3 revaccination – 35 persons. After vaccination, a significant decrease in the number of sick people was revealed in all groups: after primary vaccination, 129 (11,7%) vaccinated people got sick, after 1 revaccination 44 out of 780 (5,6%), after repeated revaccination 5 out of 284 (1,7%). In the group of people with chronic pathology, a significant decrease in morbidity was also noted after the first revaccination: out of 366 revaccinated people, 24 people (6,5%) fell ill and after repeated revaccination: 3 out of 159 (1.8%), compared with the primary vaccination complex, 61 out of 467 vaccinated (13,0%), (p<0,001).
Conclusion: In the absence of vaccination, middle-aged people are the highest risk group for developing coronavirus infection. A significant decrease in the incidence of diseases with an increase in the number of vaccinations has been established. Thus, among 1106 people who received the primary vaccine complex, 129 (11,7%) fell ill; after the complex vaccination and the first revaccination – 44 out of 780 (5,6%), in the group who received 2 and 3 revaccinations, 5 out of 284 vaccinated people fell ill (1,7%) (Px2<0,001).

Aim. To study the state of lipid and carbohydrate metabolism, body composition, liver parenchyma structure in children with chronic hepatitis C (CHC).
Materials and methods. 63 children with CHC examined at DNACIB in 2022–2023 (anthropometry, laboratory examination, bioimpedance analysis (BIA) of body composition, liver elastography with evaluation of steatosis).
Results. Abnormalities of lipid metabolism were detected in 1/3 of children with CHC even with normal and low body mass index (BMI). Signs of insulin resistance (HOMAIR>3,2) were found in 54% of children with CHC. One third of patients with insulin resistance have liver steatosis, which significantly exceeds the frequency of steatosis registration among children without insulin resistance. There was a tendency for the frequency of insulin resistance to increase in proportion to the progression of the stage of liver fibrosis. No association between hepatitis virus genotype and disorders of lipid and carbohydrate metabolism was found.
Conclusion. As a result of hepatitis C virus exposure in children with CHC, the risk of insulin resistance formation increases, which may be one of the pathogenetic mechanisms of liver steatosis development, increasing the risk of severe liver fibrosis formation and unfavorable outcome of the disease.

The aim was to analyze the prognostic value of ventilation/ gas exchange dissociation markers to predict the treatment length in patients with the acute phase of COVID-19.
Materials and methods: The analysis was performed using a database of 384 randomly selected patients from December 2021 to May 2022 with a confirmed diagnosis of the acute phase of COVID-19, aged 61±16 years. Spirometry of maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) was performed on 2,2±0,2 day of hospitalization with a portable MicroRPM device (CareFusion, UK) and measurement of surrogate oxygenation index (SpO2/FiO2), ROX index (SpO2/ FiO2)/respiratory rate) was carried out in all patients. Log-regression models were used (STATISTICA 10) to determine cutoff values for these functional variables and their ability to predict the patients length of hospital stay from the date of examination (≤ 7 vs > 7 days).
Results: The lowest sensitivity (SE) and specificity (SP) were shown in models using only the respiratory muscle strength markers MIP (SE=54%, SP=70%) and MEP (SE=73%, SP=47%), that were the same in the combination of MIP and MEP (SE=65%, SP=58%). The areas under ROC were equal to 0.6 in all three models. The models based on hypoxia markers had a higher classification power (AUC 0,7) compared to the previous three, and the sensitivity value was higher in the model using the ROX index (SE = 58% and SP = 78%), but the specificity was better in the surrogate oxygenation index model (SE = 48% and SP = 88%). A complex model based on a combination of the two integral hypoxia indices, as well as a diaphragm strength marker (SpO2/FiO2+MIP*ROX+MIP) had the best sensitivity (67%) and specificity (84%), and the area under ROC reached 0.8.
Conclusion: Indicators of respiratory muscle strength and oxygenation are suitable markers for combined models and algorithms for predicting hospital length of stay in COVID-19 patients.

Invasive meningococcal infection remains a leading cause of death among infectious diseases in children.
Aim. to investigate predictors of death in patients with invasive meningococcal infection during two periods of observation: 1991–2011 and 2012–2022.
Materials and methods. A retrospective cohort study was conducted including 143 children aged 1,5 months to 17 years old, living in the Arkhangelsk region and having had invasive meningococcal infection. The study included two periods: 1991–2011 (N=93) and 2012–2022 (N=50). Groups of recovered and deceased patients were compared.
Results. When admitted to the hospital meningococcal infection or bacterial meningitis was diagnosed in 25,5% of cases among deceased patients, and in 57,3% among survivors. More than half of the patients with an fatal outcome were not referred to the hospital after the first examination by a medical professional, unlike the recovered patients, of whom 68,8% were immediately referred to the hospital after examination. The majority of the recovered patients (82.3%) were transported to medical facilities providing specialized medical care. In the deceased group, treatment was initiated in non-specialized medical facilities in 74,5% of cases due to the distance from the regional center, where specialized care is provided. Throughout the observation period, the probability of death was higher in infants, patients with of septic shock, leukopenia, in cases requiring repeated visits by medical professional, and during initial therapy in nonspecialized medical organizations.
Conclusion. The need to repeatedly seek healthcare, a different referral diagnosis, delays in receiving specialized medical care and the necessity for evacuation to the regional center for specialized care, all increase the probability of death and justify the advisability of specific prevention of meningococcal infection.

The search for markers of early etiological verification of meningitis is an urgent task for clinical laboratory diagnostics.
Objective of the study is to determine the significance of relative and absolute content of blood lymphocyte subpopulations for early differential diagnosis of viral and bacterial meningitis in children.
Materials and methods. There was performed a clinical and laboratory examination of 61 children, 37 of them were diagnosed with viral meningitis, and 24 ones – with bacterial purulent meningitis. The control group included 15 healthy children. The relative and absolute content of the main subpopulations (T-lymphocytes: T-helpers (Th), cytotoxic T-lymphocytes (CTL), NK, B-cells) and small subpopulations (NKT, DNT- and DPT-lymphocytes, CD3+CD8br, CD3+CD8dim, CD3-CD8+NK) of lymphocytes was assessed by flow cytometry. Statistical analysis of the data was carried out.
Results. The decrease of relative and absolute content of all studied subpopulations was identified during an acute period of bacterial purulent meningitis, in comparison with the control group, with the exception of B-lymphocytes, the number of them was increased. Absolute content of all subpopulations was reduced in case of viral meningitis compared with the control group, the relative content did not have any significant differences, with the exception of an increase in the relative content of B-lymphocytes. Calculation of diagnostic sensitivity and specificity revealed the effectiveness of identification of both relative and absolute content of lymphocyte subpopulations for differential diagnosis of viral or bacterial meningitis. Identification of B-lymphocytes, NKT, CD3+CD8dim in the blood had the highest diagnostic efficiency (area under the ROC curve (AUC) ranging from 0,9 to 1).
Conclusion. Assessment of relative and absolute content of blood lymphocyte subpopulations is an effective tool for laboratory differential diagnosis of viral and bacterial meningitis and can be used as an early differential diagnostic criterion, especially in case of impossibility to analyze the composition of cerebrospinal fluid.

Impaired serum TGF-β1 production is one of the proposed mechanisms for coronavirus disease 2019 (COVID-19).
Study objective: to study blood serum TGF-β1 content in children with new coronavirus infection.
Materials and methods: a one-stage study was conducted in 119 patients with COVID-19 and compared with 118 healthy children of the same age and sex as a control group. The age range in both groups was 11.0 years. Preschoolers (0–6 years old) and schoolchildren (7–17 years old) in the group with COVID-19 were 21 (18%) and 98 (82%), respectively. Children with COVID-19 were divided into asymptomatic (n=23), mild (n=61), and moderate (n=35) subgroups. Serum samples for TGF-β1 concentration analysis were taken from all patients and tested by flow fluorimetry. The data were processed using the IBM SPSS Statistics Version 25.0 software package (International Business Machines Corporation, license No Z125-3301-14, USA).
Results: median serum TGF-β1 levels of children 0–17 years old with COVID-19 regardless of the form of severity were significantly higher than in the control group. The serum concentration of TGF-β1 in children with COVID-19 of preschool age was increased comparing to schoolchildren. Children 0-6 years old with a moderate form of coronavirus infection had high serum TGF-β1 values when compared with school-age patients.
Conclusion: elevated serum TGF-β1 levels were found in children both without clinical manifestations and with symptoms of coronavirus infection, reaching maximum values in the moderate form in children 0–6 years old.

Early assessment of HIV incidence is an important public health tool for understanding the state of the epidemic in a particular area, identifying high-risk groups, and assessing the effectiveness of HIV prevention interventions.
Objective. To assess the possibility of using the positivity rate (S/CO) in the HIV Ag/Ab immunoassay on the Alinity i analytical platform to determine the duration of infection during HIV screening.
Materials and methods. The study included 316 HIV-infected patients with different infection durations. Immunochemical analysis was performed on an Alinity i automatic analyzer (Abbott Laboratories, USA) using the Alinity i HIV Ag/Ab Reagent Kit (Abbott Laboratories, Germany) in accordance with the manufacturer’s instructions.
Results. Statistical analysis of 316 blood samples from HIV-infected patients at different stages of infection demonstrated the reactivity of the Alinity i HIV Ag/Ab test result and a dynamic increase in the positivity ratio during the first six months after the onset of the disease. Based on the data obtained, a threshold value (≤294 conventional units) was obtained for the positivity ratio, which allowed for a clear distinction between HIV-positive patients with a recent (<6 months) period of infection. At the same time, the sensitivity and specificity indicators for detecting recent infection in the CMIA analysis were 79,0% and 63,2%, respectively.
Conclusion. The additional usage of the positivity ratio in the Alinity i HIV Ag/Ab CMIA analysis meets the acceptability criteria for assessing the duration of HIV infection and can be a useful tool for analyzing the stage of the epidemic in a particular territory.

In frequently ill children with recurrent respiratory diseases (RRD), violations of local immunity and microbiocenosis of the mucous membranes can contribute to the development of acute and chronic bronchopulmonary diseases. Vaccination against major pathogens, including S. pneumoniae, can help prevent respiratory infections in children.
Objective: to study the microbiocenosis and local immunological factors of the nasopharyngeal mucosa in children with RRD, the serotype composition of S. pneumoniae in children with community-acquired pneumococcal pneumonia (CAP) and pneumococcal carriers, as well as the correspondence of the serotype landscape to the composition of modern pneumococcal vaccines.
Materials and methods: The study included 150 patients (104 children with RRD and 46 patients with CAP). To assess the condition of the nasopharyngeal mucosa cultural methods, morphofunctional, immunological and capsule PCR typing of S. pneumoniae isolates were performed. Statistical analysis was performed using the Statistica 10.0 package.
Results: The age structure was dominated by children aged 3 to 6 years (36%). The majority of patients with RRD had pronounced nasopharyngeal mucosal dysbiosis (n=60), as well as destruction of epithelial cells (n=97). These factors may predispose to the development of bronchopulmonary diseases, including community-acquired pneumonia (CAP). Capsule PCR typing of S. pneumoniae isolates from the nasopharynx was performed in 46 patients. It has been established that in the structure of nasopharyngeal carrier S. pneumoniae in children with CAP, serotypes “3” and 19F prevailed, which were also the main pathogens in pneumococcal CAP. In nasopharyngeal pneumococcal carrier, the thirteen–valent pneumococcal conjugate vaccine (PCV13) overlapped 39.6% (95%CI 27.6–53.1%) of serotypes, in pneumococcal VP – 57.2% (95% CI 36.5-75.5%), while PCV20 overlapped 22.6% more S. pneumoniae serotypes in children with CAP.
Conclusion: The strategy for the prevention of acute respiratory infections in children is immunization against pneumococcal infection, which should be carried out taking into account the regional prevalence of S. pneumoniae serotypes.

SARS-CoV-2 virus, first isolated in China in 2019, launched an epidemic and paralysed global health care in just a few mounth. In this article we present the results of a mathmatical analysis of data on morbidity for COVID-19 in Russia in 2020–2023. The structural characteristics of morbidity from this disease for the population of Moscow, St. Petersburg and Sevastopol are given based on the calculation of the Ryabtsev coefficient. The territorial concentration of morbidity in Russia was assessed dynamicaly by calculating the Herfindahl-Hirshman index.

Objective: to identify modern epidemiological features of viral acute intestinal infections in children and adolescents in the Sakhalin Region.
Materials and methods. Data on acute intestinal infection incidence obtained from statistical reports of the Rospotrebnadzor during 2021-2023 was compared with long-term average incidence rates calculated over the period before the COVID-19 pandemic (2010-2019) to perform epidemiological analysis. Incidence was calculated for different age groups; according to months of the year, monthly long-term average incidence rates were established. Index of seasonality, coefficient of seasonality, and index of seasonal growth were determined.
Results and discussion. Manifestations of acute intestinal infections epidemic process in the Sakhalin Region indicate persisting conditions for an increase in the registration of both sporadic cases of diseases and outbreaks of infectious diarrhea. Viruses were prevailing in the structure of cases of known etiology (mainly caused by rotaviruses and noroviruses). Their intra-annual dynamics showed changes in rotavirus and norovirus infection incidence rates: a shift in periods of increased incidence, a decrease in the coefficient of seasonality, and for rotavirus infection, a decrease in the index of seasonal growth. Age-adjusted rotavirus infection incidence showed predominance of the infection among preschool-aged children; norovirus infection was frequently detected among schoolchildren and adolescents. An increase in the focality index may indicate ongoing problems in the public catering sector, non-compliance with sanitary rules and hygiene standards, and untimely detection and isolation of patients with acute intestinal infections.
Conclusion. Obtained results confirm the epidemiological significance of viral gastroenteritis and the necessity of anti-epidemic measures optimization.

The article presents the results of an epidemiological study of the incidence of rabies in the population of the Republic of Cameroon in the period from 2014 to 2022. The system of epidemiological surveillance and monitoring of rabies in Cameroon is presented. According to WHO, human and animal rabies is recognized as endemic to Central Africa as a whole, and in Cameroon, in particular, this infectious goiter is classified as the first priority zoonosis within the framework of the National Program for the Prevention and Control of Recurrent and Re-emerging Zoonosis (PNPLZER). The average annual incidence of rabies recorded between 2014 and 2022 was 405.7% (95% CI: 401.9% – 409.5%). Based on the results of a retrospective epidemiological analysis, the dynamics of rabies cases among people in Cameroon is presented in accordance with data recorded at the Operational Center for Public Health Emergencies (CCOUSP). The highest rates were recorded in the period from 2018 (547.4%) to 2019 (276.8%), and the lowest in 2021 (10.7%) to 2022 (3.1%). To identify socio-demographic risk factors, a survey of rabies foci was conducted using specially designed questionnaires (epidemiological information collection cards). Mapping of registered cases of rabies in humans was carried out for 10 administrative regions of the country using the LTR QGIS (quantum GIS) program, which allowed us to show the distribution of cases across the country and dynamics over time. It has been established that the distribution of cases of the disease across the territory does not always depend on the population density in administrative districts, but is associated with specific socio-demographic risk factors such as profession, gender, age, type of animal reservoir of the virus, which affect the activity of the pathogen circulation among natural hosts.

Whooping cough continues to lead in the group of vaccine-controlled infectious diseases. It is proved that in infants (especially in the first three months of life) patients more often endure severe forms of whooping cough with the development of complications, including apnea and pulmonary hypertension. There are few studies analyzing heart rhythm disorders in children with whooping cough and their relationship to the severity of the disease. The article presents a clinical case of a patient with severe whooping cough of the first year of life. Despite the absence of leukocytosis characteristic of severe whooping cough, the child’s condition was considered as severe due to episodes of apnea accompanied by desaturation and asystole. Detection of heart rhythm disorders in children with whooping cough is important in determining the tactics of their treatment and the need for further observation by a cardiologist.

COVID-19 is an infectious disease that can progress from carrier and mild symptoms of acute respiratory infections to bilateral pneumonia, severe respiratory failure, acute respiratory distress syndrome (ARDS), multiorgan failure, sepsis and shock. One of the predictors of severe course of infection is advanced age and comorbidities. In this work we considered a clinical case of COVID-19 patient S., 86 years old, who was admitted to the hospital, to the intensive care unit on the 10th day of the disease, in an extremely severe condition. A diagnosis of bilateral polisegmental pneumonia with 70% lung involvement caused by SARS-CoV-2 virus was made. In addition to antiviral therapy with remdesivir and symptomatic therapy, pathogenetic therapy with tocilizumab was applied. On admission, the patient had leukopenia, thrombocytopenia, elevated values of COE, urea, significant elevation of inflammatory markers CRP and D-dimer, as well as pCo2. During inpatient treatment, positive dynamics of the condition and laboratory parameters were observed. The patient was discharged in satisfactory condition, all laboratory parameters were normalised, except for a slight increase in CRP and pCO2 levels. Despite the age of the patient and the severity of COVID-19 course, the combined use of drugs with multidirectional action, including tocilizumab, may improve the outcome of the disease.

Botulism is an acute infectious disease caused by a neutrotoxin produced by the bacterium Clostridium botulinum and characterized by severe bulbar lesions. Botulism is characterized by the complexity of diagnosis and in adverse cases can lead to death. At the moment, in the complex therapy of botulism, the introduction of a mixture of antitoxic serums is mandatory. In addition to specific treatment, pathogenetic therapy is performed for all patients. Specific prophylaxis is carried out with polyanatoxin to a narrow group of people in contact with Clostridium botulinum or their toxins. However, neutralizing anti-botulinum antibodies may be detected in the blood serum of a number of individuals, which have a protective effect when encountering an infection. This article presents a clinical case of severe botulism in an adult patient with simultaneous absence of symptoms of the disease in family members.
Botulinum toxin preparations have long been used in aesthetic medicine. It is worth noting that the botulinum toxin molecule has a high molecular weight and can cause an immune response with repeated injections, especially in areas rich in lymph nodes. Forming specific antibodies belong to the IgG class and may have neutralizing properties. In the above clinical case, the patient’s wife, during repeated injections of botulinum toxin, most likely, the formation of neutralizing antibodies occurred, which, in turn, protected the woman from the disease.

Currently, antibiotic-associated diarrhea caused by Clostridioides difficile (Cl. difficile) is one of the problems of the health care system in many countries of the world and the main causative agent of healthcare-associated infections. The article describes a clinical case from our own practice of the occurrence of Cl. difficile associated diarrhea (CDI) in a child in the first year of life. In the described clinical case, the child developed the first episode of CDI against the background of antibiotic therapy, which, due to the inadequate duration of treatment, led to a relapse of the disease and the development of complications in the form of sepsis. Thus, with clinical case, we want to draw the attention of practitioners to the problem of CDI in young children. Currently, despite significant changes in the diagnosis of CDI, the diagnosis of CDI in young children is challenging, requiring the development of accurate diagnostic criteria for diagnosis and the definition of additional diagnostic markers to distinguish healthy carriage from disease.