Your statement - the child was detected with Rubella virus in her blood – in probably inaccurate. Most likely an ELISA test would have been done to detect antibodies (IgG and / or IgM) against Rubella virus. These are surrogate markers or indirect evidences of infection and require care in clinical interpretation and correlation. The presence of IgG antibodies could also be a consequence of vaccination.
Rubella or German measles is a viral disease, which may occur as an acquired or a congenital infection (passed from the mother to the developing baby).
The acquired form is characterised by mild symptoms like a low-grade fever, malaise, enlargement of lymph nodes and upper respiratory symptoms followed by a rash. There is often joint involvement in adults.
Congenital rubella (also known as congenital rubella syndrome) is a severe disease affecting many organ symptoms leading to congenital defects in a baby. An infected pregnant woman may have spontaneous abortion, premature delivery or even fetal death. The severity of the disease in a baby depends on the stage of pregnancy when the infection occurs. Defects are rare if infection occurs after 20 weeks but it may be severe if occurring in the first 12 weeks. Congenital rubella may manifest itself up to the age of 4 years and is characterised by deafness, eye defects, heart defects, neurologic abnormalities and other symptoms.
The laboratory diagnosis of congenital rubella can be made by demonstration of rubella-specific IgM antibodies in the baby’s blood as this antibody persists for at least 6–12 months. The presence of serum rubella IgG titre that persists at a higher level and for a longer period than expected from passive transfer of maternal antibody (i.e., rubella titre that does not drop at the expected rate of a twofold dilution per month). The virus may be isolated from the throat and urine for a year or longer and molecular techniques like reverse transcription polymerase chain reaction (RT-PCR) can be used to detect it.
It would be best if a child specialist examines the child to check if the child is / was infected and if there are any consequences / sequelae of the same.