Measles

Measles is a highly contagious viral infection, most common in children. It is characterized by fever, cough, rhinitis, conjunctivitis, enanthem (Koplik's spots) on the mucous membrane of the cheeks or lips, and a maculopapular rash that spreads from top to bottom. Diagnosis is clinical. Treatment is symptomatic. There is an effective vaccination against measles.

Measles is widespread worldwide, with 30-40 million cases reported annually, and about 800,000 children dying from measles. In the United States, the number of cases is much lower due to vaccination; about 100-300 cases are reported each year.

ICD-10 codes

• B05. Measles.
  • B05.0. Measles complicated by encephalitis.
  • B05.1. Measles complicated by meningitis.
  • B05.2. Measles complicated by pneumonia.
  • B05.3. Measles complicated by otitis.
  • B05.4. Measles with intestinal complications.
  • B05.8. Measles with other complications (keratitis).
  • B05.9. Measles without complications.

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Epidemiology of measles

A sick person is a source of the pathogen and at the same time a reservoir for it. The contagiousness index is 95-96%.

Patients are infectious for 1-2 days before the first symptoms of measles appear and up to the end of the 4th day from the moment the rash appears. If complications such as pneumonia develop, the period of virus excretion increases. Measles is transmitted by airborne droplets. Infection is possible even with short-term contact. From the source, the virus can spread to other rooms with air currents through ventilation ducts. People who have not had measles and have not been vaccinated against it remain highly susceptible to the pathogen throughout their lives and can get sick at any age. Before the introduction of measles vaccination, 95% of children had measles before the age of 16. In recent years, measles has mainly affected children under 6 years of age. The highest mortality rate is noted in children in the first 2 years of life and adults. A large number of cases are noted among schoolchildren, adolescents, conscripts, students, etc. This is due to a significant decrease in immunity 10-15 years after immunization. Measles outbreaks are also possible among vaccinated people (67-70% of all outbreaks).

Measles is widespread; in natural conditions only humans get sick, in experiments it is possible for primates to become infected. Before the introduction of vaccination, measles outbreaks were registered every 2 years. After the introduction of mass vaccination and revaccination, periods of epidemiological well-being became longer (8-9 years). Measles is characterized by winter-spring seasonality of morbidity, the least cases of measles are in autumn.

Measles still ranks first in the overall infectious morbidity of the population in a number of countries. According to WHO, up to 30 million cases of measles are registered annually in the world, of which more than 500,000 are fatal.

After a natural measles infection, there remains a strong immunity.

Repeated diseases are rare. Immunity after vaccinations is shorter-lived (10 years after vaccination, only 36% of those vaccinated retain protective antibody titers).

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What causes measles?

Measles is caused by a paramyxovirus. It is a highly contagious infection that is spread through the air through secretions from the nose, throat, and mouth during the prodrome and early period of the rash. The most contagious period lasts several days before the rash appears and several days after the rash appears. Measles is not contagious when the rash peels.

Newborns whose mothers had measles receive protective antibodies transplacentally, which provide immunity during the first year of life. The infection provides lifelong immunity. In the United States, most cases of measles are imported by immigrants.

Pathogenesis

The entry point for infection is the mucous membrane of the upper respiratory tract. The virus multiplies in epithelial cells, particularly in the epithelium of the respiratory tract. Electron microscopy of material taken from Filatov-Belsky-Koplik spots and skin rashes reveals virus clusters. From the last days of incubation for 1-2 days after the rash appears, the virus can be isolated from the blood. The pathogen is spread hematogenously throughout the body, is fixed in the organs of the reticuloendothelial system, where it multiplies and accumulates. At the end of the incubation period, a second, more intense wave of viremia is observed. The pathogen has pronounced epitheliotropism and affects the skin, conjunctiva, mucous membranes of the respiratory tract, oral cavity (Filatov-Belsky-Koplik spots) and intestines. The measles virus can also be found in the mucous membrane of the trachea, bronchi, and sometimes in the urine.

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Symptoms of measles

The incubation period of the disease is 10-14 days, after which the prodromal period begins, which is characterized by fever, catarrhal symptoms, dry cough and tarsal conjunctivitis. Pathognomonic are Koplik's spots, which appear on the 2nd-4th day of the disease, usually on the mucous membrane of the cheek opposite the 1st and 2nd upper molars. They look like white grains surrounded by a red areola. They can spread, turning into widespread erythema on the entire surface of the mucous membrane of the cheek. Sometimes they spread to the pharynx.

Individual symptoms of measles are observed from the second half of the incubation period (weight loss of the patient, swelling of the lower eyelid, conjunctival hyperemia, subfebrile temperature in the evenings, cough, slight runny nose).

The rash appears 3-5 days after the onset of initial symptoms and 1-2 days after the appearance of Koplik spots. The maculo-like rash first appears on the face and then moves down the sides of the neck, becoming maculopapular. After 24-48 hours, the rash spreads to the trunk and extremities, including the palms and soles, gradually fading on the face. In severe cases, there may be a petechial rash and ecchymosis may appear.

During the peak of the disease, the temperature reaches 40 °C with the appearance of periorbital edema, conjunctivitis, photophobia, dry cough, abundant rash, prostration and mild itching. General symptoms and signs correlate with the rash and the period of contagiousness. By the 3rd-5th day, the temperature decreases, the patient's well-being improves, the rash begins to fade quickly, leaving a copper-brown pigmentation with subsequent peeling.

Immunocompromised patients may develop severe pneumonia and may not have a rash.

Atypical measles may occur in patients previously immunized with a killed measles vaccine, which has not been used since 1968. Older vaccines may alter the course of the disease. Atypical measles may begin suddenly, with high fever, prostration, headache, cough, and abdominal pain. The rash may appear within 1 to 2 days, often beginning on the extremities, and may be maculopapular, vesicular, urticarial, or hemorrhagic. Swelling of the hands and feet may develop. Pneumonia and lymphadenopathy are common and may be persistent; radiographic changes may persist for weeks to months. Signs of hypoxemia may develop.

Bacterial superinfection is characterized by pneumonia, otitis media, and other lesions. Measles suppresses delayed hypersensitivity, which worsens the course of active tuberculosis, temporarily neutralizes skin reactions to tuberculin and histoplasmin. Bacterial complications can be suspected by the presence of focal symptoms or relapse of fever, leukocytosis, prostration.

After the infection resolves, acute thrombocytopenic purpura may occur, which leads to the development of bleeding, which can sometimes be severe.

Encephalitis develops in 1/1000-2000 cases, usually 2-7 days after the onset of the rash, often beginning with high fever, headache, seizures and coma. In the cerebrospinal fluid, the lymphocyte count is 50-500/mcl, moderately elevated protein, but may also be normal. Encephalitis may resolve within 1 week, but may continue longer, leading to death.

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Diagnosis of measles

In conditions of low incidence, measles diagnostics is comprehensive and involves an assessment of the epidemiological situation in the patient’s environment, clinical observation over time, and serological testing.

Typical measles may be suspected in a patient with symptoms of rhinitis, conjunctivitis, photophobia and cough if he/she has had contact with a sick person, but the diagnosis is usually suspected after the appearance of the rash. Diagnosis is usually clinical, based on the detection of Koplik spots or rash. Complete blood count is not mandatory, but if done, leukopenia with relative lymphocytosis can be detected. Laboratory diagnosis of measles is necessary for outbreak control and is rarely performed. It is limited to detection of anti-measles antibodies of the IgM class in serum or epithelial cells in nasopharyngeal and urethral washes (in urine), stained by the immunofluorescence method, by PCR analysis of pharyngeal washes or urine samples, or by the culture method. An increase in the IgG level in paired sera is an accurate, but late method of diagnosis. Differential diagnosis of measles includes rubella, scarlet fever, drug rashes (eg, from sulfonamides and phenobarbital), serum sickness, roseola neonatorum, infectious mononucleosis, erythema infectiosum, and ECHO-coxsackievirus infection. Atypical measles can be simulated by a greater number of diseases due to the variability of symptoms. Signs that distinguish rubella from typical measles include the absence of a pronounced prodrome, no fever or low fever, enlargement (usually mild) of the parotid and occipital lymph nodes, and a short course. Drug rash often resembles measles rash, but there is no prodrome, no staging of the rash from top to bottom, no cough, and no corresponding epidemiological history. Roseola neonatorum is rare in children over 3 years of age; in this case there is a high temperature at the onset of the disease, the absence of Koplik's spots and malaise, the rash appears simultaneously.

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Treatment of measles

Mortality in the United States is about 2/1000, but is higher in developing countries, due to poor nutrition and vitamin A deficiency. Vitamin A supplementation is recommended in high-risk populations.

Suspected cases of measles should be reported immediately to local or state health authorities without waiting for laboratory confirmation.

Treatment of measles is symptomatic, even in cases of encephalitis. Vitamin administration reduces morbidity and mortality in children with poor nutrition, but is not necessary in others. For children over 1 year of age with visual impairment due to vitamin A deficiency, 200,000 IU orally is prescribed daily for 2 days and repeated after 4 weeks. Children living in regions with vitamin A deficiency receive it once in a single dose of 200,000 IU. Children aged 4-6 months are prescribed a single dose of 100,000 IU.

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How to prevent measles?

Measles can be prevented with the measles vaccine. Modern measles vaccines have a preventive effectiveness of 95-98%.

In most developed countries, children are given a live, attenuated vaccine. The first dose is recommended at 12 to 15 months of age, but may be given as early as 6 months during a measles outbreak. Two doses are recommended. Children immunized at less than 1 year of age require two more boosters in their 2nd year of life. Vaccination provides long-lasting immunity and has reduced the incidence of measles in the United States by 99%. The vaccine causes mild or inapparent disease. Fever greater than 100.4°F (38°C) for 5 to 12 days after vaccination occurs in less than 5% of vaccinees, followed by a rash. Central nervous system reactions are extremely rare; the vaccine does not cause autism.

Current vaccines of the national vaccination calendar:

• Live measles culture dry vaccine (Russia).
• Measles, mumps and rubella vaccination
• Ruvax live measles vaccine (France).
• MMR-II live vaccine against measles, mumps and rubella (Netherlands).
• Priorix live vaccine against measles, mumps and rubella (Belgium).

A microencapsulated live measles vaccine is currently undergoing preclinical trials, and a DNA measles vaccine is under investigation.

Contraindications to measles vaccination include systemic tumors (leukemia, lymphoma), immunodeficiencies, treatment with immunosuppressants such as glucocorticoids, alkylating agents, antimetabolites, and radiation therapy. HIV infection is a contraindication only if there is severe immunosuppression (CDC stage 3 with CD4 less than 15%). Otherwise, the risk of infection with the wild strain outweighs the risk of infection from the live vaccine. Vaccination should be delayed in pregnant women, those with fever, those with active untreated tuberculosis, or if antibodies (whole blood, plasma, or other immunoglobulins) have been used. The duration of the delay depends on the type and dose of immunoglobulin, but may be up to 11 months.

Children and adults susceptible to measles are immunized with a live measles vaccine in the event of contact with a patient in the absence of contraindications, but not later than 72 hours after the expected contact. If the period from the time of expected infection is longer, as well as for weakened individuals or those with contraindications to the administration of a live measles vaccine, normal human immunoglobulin is indicated. Immunoglobulin administered intramuscularly in the first 6 days after infection protects against measles or alleviates its course.

The method of non-specific prevention is early isolation of the patient in order to prevent further spread of the disease. Patients are subject to isolation for 7 days, if complications develop - 17 days from the onset of the disease.

Children who have not been vaccinated or sick, but who have been in contact with people sick with measles, are not allowed into children's institutions for 17 days from the moment of contact, and those who have received prophylactic immunoglobulin - for 21 days. Children are not subject to isolation for the first 7 days from the beginning of contact.

Emergency prophylaxis of measles is possible if administered within 3 days of exposure to a patient with measles. If vaccination is delayed, serum immunoglobulin is administered at a dose of 0.25 ml/kg intramuscularly (maximum dose 15 ml) immediately, with subsequent vaccination 5-6 months later, unless contraindications exist. In case of exposure to a patient with immunodeficiency, for whom vaccination is contraindicated, serum immunoglobulin is administered at a dose of 0.5 ml/kg intramuscularly (maximum 15 ml). Immunoglobulins should not be administered simultaneously with the vaccine.

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What is the prognosis for measles?

Measles has a favorable prognosis in the case of an uncomplicated course of the disease. With the development of giant cell pneumonia, encephalitis, inadequate untimely treatment, a fatal outcome is possible. In the case of the development of subacute sclerosing panencephalitis, measles in all cases has an unfavorable outcome.

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