Measles , Mumps, Rubella

Measles , Mumps, Rubella

Measles (Rubeola) Virus Infection
One of the most infectious childhood diseases known. Humans are the natural host. Caused by
the measles virus which is a paramyxovirus, genus Morbillivirus. It is 100–200 nm in diameter, with a core of single-stranded RNA. Two membrane envelope proteins are important in pathogenesis. They are the F (fusion) protein, which is responsible for fusion of virus and host cell membranes, viral penetration, and hemolysis, and the H (hemagglutinin) protein, which is responsible for adsorption of virus to cells. There is only one antigenic type of measles virus. Although studies have documented changes in the H glycoprotein, these changes do not appear to be epidemiologically impor¬tant (i.e., no change in vaccine efficacy has been observed). Measles virus is rapidly inactivated by heat, light, acidic pH, ether, and trypsin. It has a short survival time (less than 2 hours) in the air or on objects and surfaces.


Pathogenesis & Immunity:
? Virus infects URT cell lining where it multiplies locally, the infection then spreads to the regional lymphoid tissues &then multiply there (primary Viremia).
? Secondary Viremia seeds the epithelial surfaces of the body including skin, respiratory tract, conjunctiva where focal replication occurs. Virus replicates in certain lymphocytes which aid in dissemination throughout the body.
? Skin rash: due to cytotoxic T cells attacking the measles virus-infected vascular endothelial cells in the skin.
? Antibody-mediated vasculitis( so that specific antibodies coincide with appearance of rash).
? Virus shedding from infected person start 4days prior to and 4 days after the appearance of rash.
? Both neutralizing antibodies- IgG &cell mediated Immunity are involved during viremic stage of measles.