Measles is an acute respiratory infection caused by the measles virus and is highly contagious. Nowadays, measles has changed from a winter epidemic to a year-round disease, and the age of onset has changed from mainly infants under 5 years of age to mainly infants under 8 months of age and adolescents over 14 years of age, which is related to the measles vaccination. In addition, the clinical manifestations are atypical and mostly mild, which makes the diagnosis of measles difficult.
Since the introduction of universal measles vaccination in major cities in 1965, and especially since the introduction of planned immunization in the 1980s, the rate of overt measles infection has declined significantly, while occult infection has become an important form. This difference in the rate of latent infection is related to the varying levels of measles antibodies in the observed subjects, the sensitivity of the detection method, and the degree of close contact between the infected person and the measles patient.
Clinical manifestations of typical measles
1, the incubation period is generally 10 to 14 days, but also as short as about 1 week, the application of specific antibodies can be extended to about 3 weeks after passive immunization. During the incubation period, there may be a mild increase in body temperature.
2. The prodromal period is usually 3 to 4 days. The main symptoms of upper respiratory tract infection are: ① Fever, mostly moderate or above. ②Respiratory and khat symptoms. Koplik’s spot, which appears 24 to 48 hours before the onset of rash, is a small grayish-white dot with a red halo, usually on the buccal mucosa opposite the lower molars, but may involve the entire buccal mucosa and spread to the lip mucosa. Non-specific symptoms, such as general malaise, loss of appetite, and mental discomfort.
3.The rash period lasts 3 to 5 days. Most of the rash appears 3 to 4 days after the onset of fever. The rash starts as sparse irregular red papules with normal skin between the rashes, starting from behind the ears and neck, and progressing downward within 24 hours, spreading to the face, trunk and upper limbs, with the rash involving the lower limbs and feet by the third day, and in severe cases the rash often fuses and bruises may appear. Delirium, agitation and drowsiness are often present in the extreme stage of the disease, especially during high fever, and are mostly transient, disappearing after the fever subsides. During this period, there is wetness in the lungs and increased lung texture is seen on X-ray.
4.Recovery period The rash starts to subside in the order of rash 3 to 4 days after rash appearance; in the absence of comorbidities, appetite, mental and other symptoms improve subsequently. After the rash recedes, the skin remains bran-like flaking and brown pigmentation, which heals in 7 to 10 days.
Clinical manifestations of atypical measles
1, mild measles Most often seen in people who receive automatic and passive immunization. Automatic immunization that is, after vaccination against measles, the rash to maculopapular rash is common, there can also be herpes, bleeding dot rash and other forms of rash, but fever, upper respiratory tract infection and systemic toxicity are light, often without measles mucosal plaques.
Passive immunization refers to measles after gammaglobulin injection, generally mild, with an extended incubation period of 3 to 4 weeks. Measles mucosal spots can be seen, the rash is sparse, scattered on the chest and back, the rash sequence is often irregular, less pigmented spots.
2, severe measles severe disease. With high fever, delirium, convulsions for toxic measles; with circulatory collapse for shock measles; rash is hemorrhagic, the pressure does not fade for hemorrhagic measles. Hemorrhagic measles, also known as black measles, is not only the appearance of the rash from the beginning of the hemorrhagic, pressure does not fade, but also can have subconjunctival hemorrhage, nasal bleeding, cheek mucosal bleeding, hemoptysis, vomiting blood, blood in the stool, blood in the urine and vaginal bleeding.
According to foreign reports, this type of measles accounts for about 25%. The cause of hemorrhagic measles is said to be due to a decrease in platelets, which can be rebounded during the recovery period. However, this does not explain the fact that a significant number of patients with hemorrhagic measles have normal platelet counts and do not decrease, so more scholars believe that this is due to temporary damage to the integrity of the blood vessels during the acute phase. Even if there are changes in platelets, they are due to damage to megakaryocytes caused by natural infection with measles virus or infection with measles virus caused by live attenuated vaccination, resulting in impaired maturation, rather than reduced production.
3, congenital measles There are two types of prenatal and postnatal. In the past, measles in pregnancy was rare, due to the implementation of planned immunization after the proportion of adults with measles rose, the proportion of measles in pregnancy has increased relatively, but in general, the current is still a minority.
Pregnant women with measles are prone to miscarriage, preterm delivery, or stillbirth, which mostly occurs during the rash phase of measles. The measles virus can be transmitted to the fetus through the placenta. If the mother is infected with the measles virus in late pregnancy, the baby may be born with the rash or develop it soon after birth.
In a case of congenital measles admitted to the PLA 302 Hospital, the mother had the rash on the fourth day of illness and delivered the baby at a very early stage. Immediately after birth, the infant was injected with 2 ml of placental globulin. On the fourth day after birth, the infant had a light red scattered maculopapular rash on the trunk, which subsided the next day. The rash returned after 2 days and increased in number. In addition to the trunk, the rash was also seen on the head, face and extremities, partially fused. The infant had no fever, no upper respiratory tract catarrh, only a mild cough, no cox’s spots, and slightly loose stools 4-5 times a day. Both mother and child were confirmed to have measles by serum measles antibody testing of mother and infant.
4. Heterotypic measles was seen in those who were revaccinated after six months of inactivated measles vaccination. China uses live attenuated vaccine, so this type is rare.
5, infant measles generally within 6 months after birth, because the presence of maternal antibodies, infants are less likely to be infected with measles. Infants over half a year of age generally have milder symptoms.
6, adults with measles fever of 39 to 40 degrees Celsius or more in most cases, measles mucous membrane spots, toxic symptoms, often drowsy, but few complications, the prognosis is better. In addition, a small number of people can suffer from measles twice, more than half of which occurred within 2 years of the first measles.
Diagnosis
Along with the “recessive” form of infection, measles patients who have received measles vaccine tend to have atypical or significantly reduced symptoms and signs, fewer complications, and lower mortality, but a significant increase in the number of people with measles at advanced ages.
In addition, because only the mother has been vaccinated against measles, the level of measles antibodies themselves are not high, the level of protective antibodies that can be brought to the infant is even lower. Therefore, in recent years, we have seen many cases of measles in infants under 6 months of age. This suggests that future general and repeat measles vaccinations must take into account the planned immunization of infants and adults (especially adult mothers).
Laboratory tests are needed to assist in the diagnosis of atypical cases. A nasopharyngeal smear or urine sediment staining for multinucleated giant cells can be positive 1 to 2 days before and after rash onset, with a positive rate of up to 90% in the first week of disease, which is an important reference for measles diagnosis.
Immunofluorescence can also detect measles antigen, which can be used as a basis for early diagnosis. The use of enzyme-linked immunosorbent assay (EL ISA) or immunofluorescence method to detect measles IgM antibody in the serum of patients can be detected 2-3 days after the onset of measles (5-20 days after the onset of the highest positive rate), and is not interfered with rheumatoid factor, can also be used as an early and specific diagnostic method.
The level of this antibody is affected by the time of blood collection and individual immune function, especially in the early stage of the disease, the positive rate is low, which is not conducive to early diagnosis.
It has been shown that the detection of measles virus-associated gene fragments directly from pharyngeal swabs and urine of children with early measles by RT-PCR has good specificity and high sensitivity, and the positive rate is higher than that of measles IgM antibody detection, and a single specimen can be tested. Therefore, this test can be used for early diagnosis of atypical measles.
Complications of measles
1, laryngitis clinical manifestations of hoarseness, barking cough, inspiratory dyspnea and trigeminal signs, and in severe cases, death by asphyxiation.
2, pneumonia primary measles pneumonia (directly caused by measles virus) often occurs in the prodromal phase and the rash phase, pneumonia manifestations with the rash recede and gradually reduce, most of the prognosis is good. Secondary pneumonia (caused by other viral or bacterial secondary infections) mostly occurs in the late rash or rash-retreating phase, and the common bacterial pathogens are Streptococcus pneumoniae, Staphylococcus aureus, and Haemophilus influenzae, etc., and is easily complicated by pus or pneumothorax.
3, cardiovascular insufficiency Most commonly seen in children under 2 years old, clinical manifestations are shortness of breath, irritability, pallor, cyanosis, cold extremities, rapid pulse, low heart sound, rash can not be penetrated or suddenly recede, liver can be sharply enlarged, electrocardiogram examination with low voltage, T wave changes, conduction abnormalities, etc.. A few patients have myocarditis or pericarditis.
4. Neurological system
(1) measles encephalitis The incidence is about 0. 01% to 0. 5%, most of them have fever again 2 to 5 days after rash, peripheral blood leukocytosis, change of consciousness, convulsions, sudden coma and other symptoms. Cerebrospinal fluid changes are: mild mononuclear cells and protein increase, sugar normal. The mortality rate is 10%-25%; 20%-50% of survivors have motor, intellectual or psychiatric sequelae.
(2) Subacute sclerosing holoprosencephalitis is a delayed complication of acute infection, manifesting as a progressive decline in brain function, with an incidence of about 1 in 1 million, and a history of typical measles for several years before the onset of neurological symptoms, with most patients dying one to three years after diagnosis.
It is not uncommon for children with measles to experience a temporary suppression of the immune response and loss of delayed cutaneous hypersensitivity to tuberculin, which can last for several weeks, resulting in active or even disseminated foci of latent tuberculosis, leading to cornual tuberculosis or tuberculous meningitis.
Treatment of measles
1. General treatment Rest in bed, keep the room at a proper temperature and humidity, and keep the room softly lit when there are photophobic symptoms; give easily digestible and nutritious food, and replenish sufficient amount of water; keep the skin and mucous membranes clean.
2. Symptomatic treatment Small amount of antipyretic agent for high fever; sedative such as phenobarbital for irritability; cough expectorant for severe cough; antibiotics for secondary bacterial infection. Children with measles have a high need for vitamin A, which should be supplemented appropriately. Coriander 15 g can be decocted or scrubbed on the trunk and extremities to help penetrate the rash, but pay attention to keep warm.
3. Treatment of complications: Same as for internal diseases.
Control measures
1. Preventive measures
(1) Health education Measles transmission is difficult to control, most susceptible people have been infected before the isolation of patients, the isolation of patients can only play a general role. Focus on improving the immunity of susceptible people.
(2) Immunization
Passive immunization: gammaglobulin and placental globulin can prevent measles in the short term, and early injection can prevent the onset of disease in exposed individuals, but later can only reduce the onset of disease. Injection after 6 days of exposure to measles virus is not effective. Due to the success of autoimmunization and the spread of blood-borne diseases, the use of passive immunization has been greatly reduced.
Automatic immunization: The measles immunization strategy in China has been set at 8 months of age and is repeated at 7 years of age. However, each province has set a different age of reinstatement depending on its economic situation and morbidity. The effect of vaccine immunization is not as strong and persistent as that of natural infections, and some people can turn negative and get measles, while many people who are exposed to wild strains of the virus when their artificial immunity has fallen to a certain level get a hidden infection that strengthens their immunity.
There are some adverse reactions to vaccines, but immunization with overly attenuated vaccines is not ideal. Immunosuppressed individuals and pregnant women are contraindications to measles vaccination.
2. Management of patients and contacts Early detection, early diagnosis, early reporting, early isolation and early treatment of patients, isolation until 5 days after treatment. Vaccination of contacts with live measles vaccine or C-ball, medical observation, isolation if necessary, quarantine period of 21 days.
3. Measures during the epidemic period are aimed at three aspects: the transmission route and the susceptible population, the main purpose of the transmission route is to maintain air circulation and air disinfection in public places, and the key measure is to give emergency vaccination to susceptible persons in a certain age range as early as possible to interrupt the epidemic.