Diagnosis of chickenpox and herpes zoster

Clinical criteria and disease stages

Identification of the infection is based on a careful analysis of the clinical picture, which changes predictably over time. The disease may debut with prodromal phenomena, although an acute onset is observed in the vast majority of cases.

• Initial stage: Characterized by low-grade fever and moderately pronounced signs of systemic intoxication. At this point, a non-specific fine-potted or fine-macular rash may temporarily appear on the skin (the so-called rash syndrome).
• Peak stage: There is a sharp rise in body temperature accompanied by increasing weakness, headache, and loss of appetite. A key marker of this stage is the formation of vesicular exanthema. The lesions are located everywhere: on the face, torso, extremities, and invariably on the scalp. The eruptions are accompanied by intense pruritus. Concurrently, enanthema develops—involvement of the mucous membranes of the oral cavity and occasionally the genitals.
• Convalescence stage: The temperature curve returns to normal, and the patient's general well-being stabilizes. The process of crust shedding begins, starting from the peripheral part of each element. This stage lasts from one to two weeks. After the scabs completely fall off, areas of temporary depigmentation remain on the skin.

Phenomenon of false polymorphism

The most significant diagnostic sign is considered to be the specific evolutionary pattern of the lesions. The exanthema does not appear all at once, but has a distinct successive-wave character. New elements form in waves at intervals of one to two days.

It is precisely these regular new eruptions that lead to the formation of false polymorphism. Upon skin examination, the physician simultaneously observes lesions at completely different stages of development: from fresh spots and vesicles to drying elements and dense crusts. The entire cycle from primary eruption to scab shedding is usually completed by the second or third week from the onset of clinical manifestations.

Laboratory and differential diagnosis

Although in typical cases the diagnosis is established clinically, confirmation and differential diagnosis require the results of additional studies.

1. Complete blood count (CBC / hemogram): Typical shifts are a decrease in the total leukocyte count (leukopenia) and neutrophils (neutropenia) against the background of relative lymphocytosis. The erythrocyte sedimentation rate (ESR) remains normal in uncomplicated courses.
2. Serological methods: Used to assess the humoral immune response dynamically. Serum testing is performed twice: at the onset of the disease and 10–14 days later. A reliable criterion is considered to be at least a fourfold increase in specific antibody titer. Laboratory practice utilizes complement fixation tests (CFT), hemagglutination inhibition tests (HIT), and enzyme-linked immunosorbent assay (ELISA).
3. Molecular-biological diagnostics (PCR): This method is reserved for diagnostically complex situations. It aims to detect the viral genetic material in various biological fluids: whole blood, vesicle exudate, or cerebrospinal fluid (CSF).

During the diagnostic process, pathologies with similar skin manifestations must be excluded. The differential diagnosis includes impetigo, vesicular reticulosis, and various toxic-allergic reactions, including polymorphic exudative erythema.

High-risk categories

Special vigilance during history taking should be exercised with patients in whom infection leads to the development of extremely severe forms of the pathology. Such risk groups include:

• Individuals suffering from hematological disorders (particularly leukemias).
• Patients with diagnosed malignancies.
• Patients receiving immunosuppressive therapy, including glucocorticosteroid administration.
• Individuals with severe concomitant chronic pathology: chronic kidney disease (CKD), collagenoses, bronchial asthma, and autoimmune diseases.
• Patients scheduled for donor organ transplantation.

Preventive measures

Preventive measures upon infection detection are divided into isolation-quarantine measures and emergency protection methods.

Non-specific prophylaxis: Isolation of the infected person ceases five days after the fixation of the last fresh rash element. In preschool childcare facilities, quarantine is imposed: children who have been in contact are isolated for a period of 21 days. If the exact date of contact is reliably established, isolation is appropriately carried out exclusively from the 11th to the 21st day of the incubation period.

Passive immunization: Implies emergency intramuscular administration of convalescent serum immunoglobulin (at a dosage of 1.5–3 ml). This measure is strictly indicated for debilitated, previously uninfected children, as well as pregnant women if infection occurred less than five days before delivery or within the first 48 hours after it.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Rules for taking an epidemiological history and identifying the source of infection.
• Differential diagnosis with impetigo and vesicular reticulosis.
• Clinical picture of toxic-allergic rashes (polymorphous exudative erythema).
• Specifics of managing pregnant women at risk of infection.
• Interpretation of serial results of serological reactions (CF test, HI test, ELISA) over time.

Other topics in the "Respiratory Infections" section

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