Rubella, also known as German measles, is a respiratory infection that is caused by Rubella Virus. This virus is a member of genus arbovirus included in family, Togaviridae. The disease has some resemblance with both scarlet fever and measles but differing from these in its short course. It is characterized by the pale red or bright red rash on the body.
DISTINCTIVE PROPERTIES OF RUBELLA VIRUS
Rubella virus is a circular virus 60nm in diameter. Its genome consists of a single-stranded linear RNA of positive configuration. The molecular weight of RNA , has been estimated 3.2 x 106 .The genome is placed inside a capsid that is surrounded by a lipoprotein envelope. The virus contains a hemagglutihin that can agglutinates erythrocytes from1-day-old chicks, geese, and pigeons. There is only one serotype of rubella virus. Rubella virus can be cultivated by using a number of different cell types.
Rubella is highty contagious disease. The virus is harbored in the upper respiratory tract of infective persons and is discharged in the nasal secretions. It is transmitted by inhalation of infective droplets and person-to-person contact. Both symptomatic and nonsymptomatic individuals can shed virus and spread the disease to others. The incubation period of rubella is 14-21 days averaging 18 day. During this period the virus replicates in the mucosa of upper respiratory tract from where it migrates to blood circulation causing viremla, During viremia stage the virus is usually found in the throat, blood, and feces.
Rubella begins aa mild illness. The patient complains of malaise and fever. Mild conjunctivitis and lymphadenopathy may be present. The distribution of lymphadenopathy is characteristic and involves the suboccipital, postauricular and post cervical groups pf lymph nodes. Splenomegaly may be present.
The prodromal phase of the disease is followgd by eruptive or exanthematous phase. This phase usually begins within the first week of the initial symptoms. The eruptive phase is characterized by the appearance of rash first on the forehead then spreads to neck trunk and the Iimbs. The macular rash is of pinkish red color and discrete. The rash usually fades by the second day and rarely persists beyond the third day.
CONGENITAL RUBELLA SYNDROME
The major significance rubella lies in the fetal damage. In the pregnant woman, particularly when she gets Involved in the disease during the first trimester. The virus accurs in the maternal hIood from where it is transferred to fetus through placenta. Congenital rubella is characterized by the presence of fetal cardiac malformation, eye Iesions (especIally cataracts), microcephaly, mental retardation and deafness. Other clinical manifestations may Include hepatosplenomegaly, myocarditis, thrombocytopenia, intrauterine growth retardation, interstitiaI pneumonia, hepatitis and metaphyseal bone Iesions. It has been noted that some of the congenitally infected babies do not show any abnormality at birth. However, the defects may appear a few months later. Here It should be emphasized that rubeIIa virus is not IethaI to fetal tissue but it inhibits the mitosis that leads to the underdeveloped organs or tissues.
Complications are very rare. They include superadded pulmonary bacteriaI infections, arthraIgia, encephaIitis and hemorrhagic manifestations due to thrombocytopenia.
Natural infection leads to the production of antibodies that reach to a peak within 2-3 weeks after onset. Production of sIgA also takes pIace in the respiratory tract. These antibodies provide lifelong immunity.
Diagnosis can be made on the cIinicaI grounds. However, under certain circumstances isotation of rubella virus becomes essential. This can be achieved by Inoculating nasal secretions, urine, tissues, and feces into a variety of cell cultures. Serodiagnosis is performed in order to demonstrate rising titer of specific antibody in two successive blood samples taken 14 days apart. Most popular techniques incIude ELISA, hemagglutination inhibition test, latex agglutination, passive hemagglutination, and enzyme immunoassay.
The most effective measure for the control of rubella is vaccination. Two types of vaccines are commercially available: monovalent Iive attenuated vaccine and trivalent measles/mumps/rubella (MMR) vaccine. Vaccination is essentially recommended to children between the age at 1 year and puberty and aII seronegative individuals. Women of childbearing age should also be immunized with the understanding that they not become pregnant for 3 months after the vaccination.Hospital staff, particularly those who have close contact with pregnant women, should also be immunized. Vaccination leads to a lifelong immunity.