Measles virus

2021-08-16 05:47 PM

Measles virus infects the upper respiratory tract or can enter the eye and replicates in adjacent epithelial cells and lymphoid tissue

This family of viruses is a group of agents that differ in their pathogenicity, distribution in the animal kingdom, and in their biology.

These viruses are very close in shape and structure to the Orthomyxoviridae family, but they have different properties such as size from 150 to 700 nm, RNA with molecular weight from 5 to 7,106 daltons, small coiled nucleocapsid with sugar 12 to 18 nm in diameter, the frequent presence of a cell-binding protein (which induces syncytosis), the persistence of antigens...

The family Paramyxoviridae is divided into 3 genera:

Paramyxovirus: parainfluenza virus and mumps virus.

Morbillivirus: measles virus.

Pneumovirus: respiratory syncytial virus.

The properties of the virus

Structure

The shape of the virus is mainly spherical, but sometimes thread-shaped, about 140 nm in size. Virus contains single-stranded RNA, nucleocapsid symmetric spiral, enveloped. The surface of the viral envelope contains red blood cell agglutination factors.

Resistance

 Viruses are sensitive to ethers. The measles virus has a high resistance. It can survive many days at 360C, at 220C it can live for more than 2 weeks.

Antigen properties

Ribonucleoprotein antigens are also known as complement-conjugated antigens.

RBC agglutinin antigen: located on the surface of the envelope. Measles virus agglutinates monkey red blood cells.

Hemolymph: The hemolytic property of the measles virus was described by Peries in 1961. The intact virus particle, as well as the detached erythrocyte agglutination factor, have hemolytic activity.

Viral culture

To culture measles virus, people often use the culture of human and monkey kidney cells, human amniotic membrane cells, chicken embryo cells... Measles virus in the process of development in cell culture has caused effects Pathological cells such as the formation of multinucleated giant cell clumps and eosinophilic inclusions in the cytoplasm and nucleus.

Viral pathogenicity

Measles is a contagious and epidemic rash caused by the measles virus.

The spread of the virus in the body

The measles virus infects the upper respiratory tract or can enter the eye and multiplies in adjacent epithelial cells and lymphoid tissue. During a brief primary viremia, the virus is dispersed to more distant lymphatic tissue. Viral replication in the respiratory tract and conjunctiva causes symptoms such as runny nose, dry cough, headache, conjunctivitis, fever, and Koplick's sign in the oral mucosa. Viral infections occurring at the end of the incubation period cause the virus to spread further into the lymphatic tissue and cause a skin rash. Measles virus also replicates and destroys macrophages and lymphocytes, causing immunodeficiency, especially cell-mediated immunity, and delayed hypersensitivity. Immunodeficiency in children with measles plays an important role in the mechanism of infection with tuberculosis or other bacteria after measles (primary tuberculosis, post-measles bronchopneumonia,).

Epidemiology

Measles is one of the most contagious diseases, circulating in high population density areas, occasionally emerging into epidemics, adults often have been infected once.

The disease is transmitted directly through the respiratory tract and mucous membranes of the eyes. Most contagious at onset and during rash. For children over 6 months old, the immunity passed on by the mother has expired, at that time the receptivity increases very high.

Measles worldwide is caused by a unique and persistent virus. Immunity acquired after recovery is stable for life, and second cases are rare.

Laboratory diagnostics

Virus isolation and identification

Virus isolation from throat rinses and blood 48 hours before rash appearance and 30 hours after rash. Use cultured specimens in receptor cell cultures. Virus identification by looking for giant cells, acidophilic corpuscles in the cytoplasm and in the nucleus. Or use neutralization in cell cultures.

Serological diagnosis

Serum reactions such as neutralization and complement combination reactions can be used.

Prevention and treatment

Prevention

Isolate the measles patient until he/she recovers.

For children who have been in contact with a measles patient, it is advisable to use the serum of a person who has had measles-containing a large amount of measles-specific gamma globulin, which can prevent the disease from occurring or at least reduce the risk of disease. greatly ease the progression of the disease.

Vaccine-specific prevention is the most effective way to prevent disease. There are two types of vaccines:

+ Dead measles vaccine: currently not used because it requires multiple injections, causes weak immunity, and often causes hypersensitivity when repeated injections.

+ Live attenuated measles vaccine: The vaccine is injected 1 x 0.5ml dose under the skin on the outside of the arm. The effectiveness of the vaccine is up to 95%.

Local and systemic reactions are mild 6 - 8 days after vaccination. Measles vaccine should not be given to infants who are too young because, under 6 months of age, infants still have measles antibodies passed on by their mothers. It is best to vaccinate children 9 - 11 months old.

Currently, our country is using a live attenuated measles vaccine in the expanded immunization program.

Treatment

In uncomplicated cases, treatment is only aimed at addressing the symptoms. Let the child lie down, eat easily digestible foods. Antibiotics should only be used when there is a complication of secondary infection. Using gamma globulin specific against measles for treatment, has a very good effect