Etiology and viral properties
The measles pathogen belongs to the genus Morbillivirus. It is a spherical, enveloped RNA-containing virus. Important glycoprotein structures — "spikes" — are located on the surface of the virion:
- Hemagglutinin (H) — ensures the attachment of the virus to target cells. It binds to the specific CD46 receptor, which is present on human mucosal epithelial cells and neuroglia.
- Fusion protein (F) — is responsible for the penetration of the viral nucleocapsid into the cell. In addition, this protein causes infected cells to fuse with healthy ones, forming syncytia (giant multinucleated non-viable cells). Through this mechanism, the virus spreads through tissues while avoiding contact with neutralizing antibodies.
The measles virus is extremely unstable in the external environment. It is inactivated by sunlight within a few minutes, and is destroyed by drying, heating (above 56 °C), and treatment with standard disinfectants. However, the pathogen tolerates low temperatures well.
Epidemiology and pathogenesis
The only source of infection is a sick person. Transmission occurs via airborne droplets during conversation, sneezing, and coughing. Due to high volatility, the virus easily spreads through ventilation ducts and stairwells. The peak of contagiousness occurs throughout the catarrhal period and on the first day of the rash.
The entryway for the infection is the epithelium of the respiratory tract and conjunctiva, where primary replication of the virus takes place. Then the pathogen penetrates into the lymph nodes and blood. Viremia develops, during which the virus is carried throughout the body, settling in secondary foci (skin, mucous membranes, and less commonly the CNS).
A crucial feature of the pathogenesis is "measles-induced anergy". The virus is capable of infecting lymphocytes, which leads to the suppression of immune responses and sharply increases the risk of secondary bacterial infections.
Clinical periods of the disease
The incubation period averages from 8 to 17 days. The disease runs a cyclical course and is divided into several stages:
- Initial (catarrhal) period (3–4 days). The disease debuts acutely: chills, temperature up to 38–39 °C, severe headache. Symptoms of respiratory and ocular involvement rapidly increase: profuse lacrimation, photophobia, facial puffiness, conjunctival hyperemia, harsh dry cough. On the 3rd day, pathognomonic Koplik's spots — small whitish lesions with a red halo — appear on the buccal mucosa (opposite the lower molars).
- Height of illness (eruption) period (3–4 days). Characterized by the appearance of a maculopapular rash (exanthema). The rash spreads strictly in a step-by-step manner "from top to bottom": first covering the face and neck, the next day the torso, and then the extremities. During this period, intoxication symptoms are at their maximum.
- Convalescence (pigmentation) period (5–8 days). The inflammatory foci in the skin undergo changes: due to erythrocyte breakdown and hemosiderin accumulation, the rash darkens (pigments). Furfuraceous desquamation begins, and the patient's general condition normalizes.
Diagnosis, treatment, and complications
The diagnosis is established based on the characteristic clinical picture (puffy face, Koplik's spots, step-by-step rash) and epidemiological history. Serological methods (ELISA, HI assay) are used for laboratory confirmation to detect acute IgM class antibodies.
Treatment of uncomplicated measles is carried out on an outpatient basis: bed rest, abundant fluid intake for detoxification, care of the oral and ocular mucous membranes, and symptomatic therapy (antipyretics, bronchodilators). Severe cases require immediate hospitalization.
The most formidable complications are those involving the CNS. The virus is capable of crossing the blood-brain barrier, causing acute encephalitis. With defective replication, the virus can persist in neurons, which leads to fatal subacute sclerosing panencephalitis (SSPE) 5–10 years later.
Briefly: answers to topical questions
Is there a specific etiotropic therapy for measles?
Specific etiotropic therapy for measles is not described in the cited sources. Treatment is carried out with pathogenetic and symptomatic agents: bed rest, frequent small sips of fluid monitored by diuresis, antipyretics for hyperpyrexia/temperature above 38.5°C, multivitamins, antihistamines, bronchodilators and mucolytics for cough/false croup, care of the oral and ocular mucous membranes. For bacterial complications, antibacterial therapy is prescribed: macrolides, semisynthetic penicillins, first- and second-generation cephalosporins.
When are routine vaccination and revaccination against measles carried out?
Routine vaccination against measles is administered to children starting at 12 months of age in accordance with the National Immunization Schedule. Live measles vaccine is administered subcutaneously, once. The timing of revaccination is not indicated in the presented sources.
Koplik's spots visually resemble spilled semolina on the buccal mucosa — this is the earliest and most accurate marker of measles before the appearance of the skin rash.
Class and exam questions
Why does the measles rash leave pigmentation behind?
In foci of skin inflammation, diapedesis (exit) of erythrocytes from vessels occurs. Their subsequent destruction leads to the local accumulation of the pigment hemosiderin.
Can you catch measles through household items?
Contact transmission is practically impossible, as the measles virus is extremely unstable in the external environment and quickly dies outside the human body.
What are measles syncytia?
These are giant multinucleated non-viable cells that form as a result of the fusion of infected and healthy cells under the action of the viral F protein.
What else to study on this topic
- Features of the differential diagnosis of measles with rubella and scarlet fever.
- Subacute sclerosing panencephalitis (SSPE): pathogenesis of virus persistence in the CNS.
- Mechanisms of the development of "measles-induced anergy" and the risk of secondary bacterial pneumonia.
- Specific prevention of measles and causes of morbidity among vaccinated individuals.
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