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What causes measles?
Last reviewed: 19.11.2021
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Pathogen of measles - a large virus with a diameter of 120-250 nm, belongs to the family Paramyxoviridae, the genus Morbillivirus.
Unlike other paramyxoviruses, measles virus does not contain neuraminidase. The virus has haemagglutinating, hemolytic and symplast-forming activity.
Pathogenesis of measles
The entrance gates for the virus are the mucous membranes of the upper respiratory tract. There are indications that the conjunctiva of the eye can also be the gateway to infection.
The virus penetrates the submucosa and the lymphatic pathways of the upper respiratory tract, where its primary reproduction occurs, then enters the blood, where it can be detected from the first days of the incubation period. The maximum concentration of the virus in the blood is observed at the end of the prodromal period and on the 1st day of the rash. These days the virus is present in large quantities and in the mucosal membranes of the upper respiratory tract. From the 3rd day of the rash the secretion of the virus decreases sharply and it is not detected in the blood. Viral neutralizing antibodies begin to predominate in the blood.
The measles virus has a special tropism for the central nervous system, respiratory tract and gastrointestinal tract. It has now been established that the measles virus can persist for a long time in the brain and cause a chronic or subacute form of infection. Subacute sclerosing panencephalitis is also associated with persistent measles infection.
The appearance of a rash on the skin should be considered as the result of fixation in the vessels of the skin of immune complexes formed during the interaction of antigen and antibody viruses. Cells of the epidermis are dystrophized, necrotic, and then intensified keratinization of the epidermis occurs in the affected areas, followed by rejection (ecdysis). The same inflammatory process occurs also on the mucous membranes of the oral cavity. Degenerate, and then the horny epithelium grows turbid, rises, forming small whitish foci of superficial necrosis (spots of Filatov-Koplik).