What is Measles?
Measles (Latin Morbilli) is an acute infectious viral disease with a high level of susceptibility (the contagiousness index approaches 100%), which is characterized by a high temperature (up to 40.5 ° C), inflammation of the mucous membranes of the oral cavity and upper respiratory tract, conjunctivitis and characteristic maculopapular rash of the skin, general intoxication.
Measles has been known since antiquity. Its detailed clinical description was compiled by the Arab physician Razes (IX century), the British T. Sidnam and R. Morton (XVII century). Since the XVIII century, measles is considered as an independent nosology. A. Enderson and D. Goldberger (1911) proved the viral etiology of the disease. The causative agent was identified by D. Anders and T.K. Peebles (1954). Effective seroprophylaxis of measles was developed by R. Degkvits (1916-1920). The live vaccine, used since 1967 for routine vaccination, was developed by A.A. Smorodintsev et al. (1960).
What Causes Measles
The causative agent of measles is an RNA virus of the genus morbillivirus, a family of paramyxoviruses, has a spherical shape and a diameter of 120-230 nm. It consists of nucleocapsid – RNA helix plus three proteins and the outer shell formed by two types of matrix proteins (surface glucoproteins) – one of them is hemagglutinin, the other is a “dumbbell-shaped” protein.
All known strains of the virus belong to the same serovar; antigenic structure similar to pathogens of parainfluenza and mumps. The most important antigens are hemagglutinin, hemolysin, nucleocapsid and membrane protein.
The virus is unstable in the environment, quickly dies outside the human body from the effects of various chemical and physical factors (irradiation, boiling, treatment with disinfectants). At room temperature, it remains active for about 1-2 days, at low temperature – for several weeks. The optimal temperature for virus preservation is (-15) – (- 20) ° С.
Despite the instability to the effects of the environment, there are cases of the spread of the virus over long distances with an air flow through the ventilation system — during the cold season in one single building. Attenuated strains of measles virus are used to produce live measles vaccine.
Pathogenesis during Measles
The path of transmission of measles is airborne, the virus is excreted into the external environment in large numbers by a sick person with mucus during coughing, sneezing, etc.
The source of infection is measles in any form, which is contagious to others from the last days of the incubation period (last 2 days) to the 4th day of the rash. From the 5th day of the rash, the patient is considered non-infectious.
Measles mostly affects children between the ages of 2 and 5, and much less often adults who have not experienced this disease in childhood. Newborns have colostral immunity, transferred from their mothers if they have had measles before. This immunity is maintained for the first 3 months of life. There are cases of congenital measles in transplacental infection with fetal virus from a sick mother.
After suffering the disease, a stable immunity develops, recurrent disease of the human measles, without a concomitant pathology of the immune system, it is doubtful, although such cases have been described. Most cases of measles are observed in the winter-spring (December-May) period, with an increase in incidence every 2-4 years.
Currently, in countries that conduct total measles vaccination, the disease is found in the form of isolated cases or mini-epidemics.
The gates of infection are the mucous membranes of the upper respiratory tract and possibly the conjunctiva. After primary replication in epithelial cells and regional lymph nodes, the pathogen enters the bloodstream, primary viraemia develops already in the incubation period. As a result, the virus disseminates, is fixed in various organs and secondarily accumulates in the cells of the macrophage system. In organs (lymph nodes, tonsils, lungs, intestines, liver and spleen, myeloid tissue of the bone marrow) small inflammatory infiltrates develop with proliferation of the reticuloendothelial and the formation of multicore giant cells. During the incubation period, the number of viruses in the body is still relatively small and can be neutralized by administering a measles immunoglobulin to persons who have come into contact with measles patients no later than the 5th day after contact.
With the advent of catarrhal symptoms of the disease coincides the emergence of the second wave of viremia. The maximum concentration of the virus in the blood remains during the entire catarrhal period and the first day of the rash, then drops sharply. By the 5th day of a rash, neutralizing antibodies appear in the blood, and the virus is no longer detected.
Possessing tropism for epithelial cells of the mucous membranes and the central nervous system, the virus mainly affects the upper respiratory tract (sometimes also the bronchi and lungs), the conjunctiva, to a small extent the gastrointestinal tract. Inflammation develops with the appearance of giant cells in the lymphoid formations of the intestine, as well as in the central nervous system, as a result of which it becomes possible to develop complications such as meningitis and meningoencephalitis. The protein components of the virus and biologically active substances released in response to the circulation of the virus give catarrhal inflammation in the affected organs an infectious-allergic character. A specific inflammatory focal process with an allergic reaction, epithelium dystrophy, increased vascular permeability, perivascular infiltration and edema underlies the formation of measles enantema, Filatov-Koplik-Velsky spots on the mucous membrane of the cheeks and lips, and later exanthema.
Systemic damage to the lymphoid tissue, macrophage elements, CNS (reticular formation, hypothalamus, etc.) leads to transient suppression of humoral and cellular immune responses. The weakening of the activity of nonspecific and specific protection factors inherent in measles, extensive lesions of the mucous membranes of the respiratory tract and gastrointestinal tract, as well as a decrease in vitamin metabolism deficient in vitamins C and A constitute a group of factors contributing to the emergence of various bacterial complications.
After recovery, immunity is formed with lifelong preservation of measles antibodies in the blood. However, they believe that the virus can remain in the human body for a long time and be responsible for the development of a slow infection in the form of multiple sclerosis, subacute sclerosing panencephalitis, and possibly some systemic diseases – systemic lupus erythematosus, systemic scleroderma, rheumatoid arthritis.
Microscopic picture: respiratory tract mucosa – edema, vascular plethora, foci of necrosis, areas of epithelial metaplasia, focal lymphohistiocytic infiltration in the submucosal layer. Reticuloendothelial system – Warthin-Finkeldey cells. Skin – changes in the papillary layer of the dermis in the form of edema, vascular congestion, hemorrhages with perivascular lymphohistiocytic infiltration, focuses of necrosis in the epidermis.
Symptoms of Measles
The incubation period averages 1-2 weeks, with passive immunization with immunoglobulin, it can be extended to 3-4 weeks. Existing clinical classifications emit a typical form of measles of varying degrees of severity and an atypical form. The cyclical course of the disease in its typical form allows us to distinguish three consecutive periods of clinical manifestations of measles:
- catarrhal period;
- a period of rash;
- recovery period.
Catarrhal period begins acutely. General malaise, headache, loss of appetite, sleep disturbance appear. Body temperature rises, with severe forms it reaches 39-40 ° C. Signs of intoxication in adult patients are much more pronounced than in children. From the first days of the disease, a runny nose with copious mucous, sometimes mucopurulent discharge is noted. An obsessive dry cough develops, in children it often becomes rough, “barking”, accompanied by hoarseness and (in some cases) stenotic breathing. At the same time, conjunctivitis develops with eyelid swelling, conjunctival hyperemia, scleral injection and purulent discharge. Often in the morning eyelids stick together. The patient is irritated by a bright light. On examination of children with measles, they detect puffiness of the face, hyperemia of the mucous membrane of the oropharynx, grit of the posterior pharyngeal wall. In adults, these symptoms are mild, but lymphadenopathy (mainly of the cervical lymph nodes) is observed, hard breathing and dry rales in the lungs are heard. In some patients, a short pasty stool is noted.
On the 3-5th day, the patient feels somewhat better, fever decreases. However, after a day, the manifestations of intoxication and catarrhal syndrome again increase, the body temperature rises to high numbers. At this moment, a cardinal clinical diagnostic sign of measles, Filatov-Koplik-Velsky spots, can be found on the cheek mucosa opposite the small molars (less often on the mucous membrane of the lips and gums). They are a few protruding and tightly fixed white spots, surrounded by a thin border of hyperemia (type of “semolina”). In children, elements usually disappear with the appearance of exanthema; in adults, they may persist during the first few days. Slightly earlier than Filatov-Koplik-Velsky spots or simultaneously with them on the mucous membrane of the soft and partially hard palate, a measles enantema appears in the form of red spots of irregular shape, the size of a pinhead. After 1-2 days, they merge and are lost on the general hyperemic background of the mucous membrane.
At the same time, with an increase in symptoms of intoxication, it is sometimes possible to observe dyspeptic phenomena. In general, the catarrhal period lasts 3-5 days, in adults it sometimes lasts up to 6-8 days.
The period of a rash replaces the catarrhal period. Characterized by the appearance of bright spotted papular exanthema, which has a tendency to merge and the formation of figures with areas of healthy skin between them.
- On the first day, elements of the rash appear behind the ears, on the scalp, and then on the same day, appear on the face and neck, upper chest.
- On the 2nd day of the rash, a rash covers the torso and upper arms.
- On the 3rd day, the elements of exanthema appear on the lower limbs and distal parts of the hands, and turn pale on the face.
A downward sequence of lesions is characteristic of measles and is a very important differential diagnostic character. In adults, the rash is more abundant than in children, it is coarse-papular, often confluent, with a more severe course of the disease, the appearance of hemorrhagic elements is possible.
The period of rash is accompanied by an increase in catarrhal phenomena – runny nose, cough, lacrimation, photophobia – and the maximum severity of fever and other signs of toxemia. When examining patients often reveal signs of tracheobronchitis, moderate tachycardia and arterial hypotension.
The period of convalescence (pigmentation period) is manifested by an improvement in the general condition of the patients: their well-being becomes satisfactory, the body temperature returns to normal, and catarrhal symptoms gradually disappear. Elements of the rash fade and fade in the same order in which they appeared, gradually turning into light brown spots. In the subsequent pigmentation disappears in 5-7 days. After its disappearance, it is possible to observe chipped skin peeling, mainly on the face. Pigmentation and desquamation are also diagnostically important, although retrospective, signs of measles.
During this period, a decrease in the activity of non-specific and specific protection factors (measles anergy) is noted. The reactivity of the body is restored slowly, over the next few weeks and even months, there is a reduced resistance to various pathogenic agents.
Mitigated measles. Atypical form that develops in persons who have received passive or active immunization against measles or who have previously experienced it. It is characterized by a longer incubation period, a light course with little pronounced or not at all pronounced intoxication, shortened catarrhal period. Spots Filatov-Koplika-Velsky most often absent. A rash is typical, but a rash may occur simultaneously over the entire surface of the trunk and extremities or have an ascending sequence.
Abortive measles also refers to atypical forms of the disease. It begins as a typical form, but is interrupted after 1-2 days from the onset of the disease. A rash appears only on the face and trunk, an increase in body temperature is usually observed only on the first day of the rash.
Also found subclinical variants of measles, detected only during serological examination of paired serum.
The most common complication of measles is pneumonia. Laryngitis and laryngotracheobronchitis in young children can lead to the development of false croup. Meet stomatitis. Meningitis, meningoencephalitis and polyneuritis more often observed in adults, these conditions usually develop in the pigmentation period. The most formidable, but fortunately, rare complication (more often in adults) is measles encephalitis.
Laboratory data for measles:
lymphopenia, leukopenia, in the case of bacterial complications – leukocytosis, neutrophilia. With measles encephalitis – an increased content of lymphocytes in the cerebrospinal fluid. 1-2 days after the rash, specific IgM rises. After 10 days of IgG. To identify specific measles antibodies, hemagglutination reaction is used. In the early stages of the disease, the virus is detected by immunofluorescence.
Isolation of the virus from nasopharyngeal swabs and setting of serological reactions (RTGA, RSK and PH in paired sera) is rarely used in clinical practice, since their results are retrospective.
Measles should be differentiated from rubella, scarlet fever, pseudotuberculosis, allergic (medicinal, etc.) dermatitis, enterovirus infections, serum sickness and other diseases accompanied by the appearance of skin rashes.
Measles are distinguished by a complex of the main clinical manifestations in the catarrhal period: intoxication, runny nose with copious secretions, obsessive coarse, barking cough, hoarseness, pronounced conjunctivitis with eyelid swelling, vascular injection of sclera and purulent discharge, photophobia, appearance of a cardinal clinical diagnostic sign. Koplika-Velsky for the 3-5th day of illness. Then there is a bright spotty-papular rash with a tendency to merge. A very important differential diagnostic feature characteristic of measles (with the exception of mitigated) is the downward sequence of eruptions.
Symptomatic treatment of measles, in the case of pneumonia or other bacterial complications, antibiotics are indicated, in severe cases of croup, corticosteroids are used. Ribavirin has been shown to be effective in vitro. For the prevention and treatment can be used large doses of vitamin A.
Uncomplicated forms are often treated at home. Hospitalized patients with severe and complicated forms, as well as for epidemiological indications. The duration of bed rest depends on the degree of intoxication and its duration. A special diet is required. Etiotropic therapy is not developed. With intoxication struggle with the appointment of a large amount of fluid. Carry out oral and eye care. Eliminate the irritating effects of direct sunlight and bright artificial light. Also prescribe antihistamine and symptomatic drugs. There are reports of the positive effect of interferon (leukinferon) in the appointment in early stages of the disease in adult patients. In some cases, with severe and complicated course of measles, antibiotics may be prescribed. When measles encephalitis is necessary to use large doses of prednisone under the guise of antibacterial drugs.
Total double vaccination of children with measles vaccine at the age of 1 year and 6 years. The measles vaccine was first created in 1966.
Live measles vaccine (JCC) is used for active immunoprophylaxis of measles. It is prepared from the vaccine strain L-16 grown in the culture of embryo cells of Japanese quail. In Ukraine, the use of ZhKV “Ruvaks” (Aventis-Pasteur, France), a comprehensive vaccine against measles, rubella and mumps MMP (Merck Sharp Dome, USA) is allowed.
Live measles vaccine is vaccinated in children who have not had measles since the age of 12-15 months. Revaccination is carried out in the same way as vaccination, once in 6 years, before entering school. Its goal is to protect children who, for one reason or another, have not developed immunity. Immunization of at least 95% of children provides a good protective effect. To monitor the state of the immunity of the population conduct selective serological studies. The WHO Regional Committee for Europe at its 48th session (1998) adopted the objectives of the Health 21 program, which aims to eliminate measles from the Region by 2007 or earlier. By 2010, elimination of the disease must be registered and certified in each country.
Passive immunization is carried out by the introduction of measles immunoglobulin.