Primary post natal Rubella virus infection is typically a self limiting mild disease . In utero infection with Rubella IgM may severely damage the fetus . Primary prenatal infections may have devastating effects leading to Congenital Rubella Syndrome (CRS) in the neonates. This syndrome includes low birth weight, cataract, deafness, congenital heart disease and mental retardation. A positive Rubella IgG antibody indicates successful immunization or past exposure. The result of a single antibody determination should not be used to diagnose recent infection. Acute and convalescent sera should be collected 2-4 weeks apart and a rising titer of more than 30% is considered significant. In case of acute primary infection, IgM has been detected 4-15 days after the appearance of rash. The levels begin to decline after 36-70 days but infrequently may be detected upto 180 days. In suspected cases of primary infection, the optimum time of specimen collection is 1-2 weeks after the onset of rash.