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incidence of congenital toxoplasmosis increases as pregnancy progresses; conversely, the severity of
congenital toxoplasmosis is greatest when maternal infection is acquired early during pregnancy. A
majority of infants infected in utero are asymptomatic at birth, particularly if maternal infection occurs
during the third trimester, with sequelae appearing later in life. Congenital toxoplasmosis results in
severe generalized or neurologic disease in about 20% to 30% of the infants infected in utero;
approximately 10% exhibit ocular involvement only and the remainder are asymptomatic at birth.
Subclinical infection may result in premature delivery and subsequent neurologic, intellectual, and
audiologic defects. Rubella: Primary postnatal rubella infection (German or 3-day measles) is typically
a mild, self-limiting disease characterized by a maculopapular rash, fever, malaise, and
lymphadenopathy. Conversely, primary prenatal rubella infections may have devastating results. In
utero infections may severely damage the fetus, particularly if the infection occurs during the first 4
months of gestation. Congenitally infected infants may exhibit 1 or more defects including congenital
heart disease and mental retardation. Prior to the introduction of the rubella vaccines, approximately
15% of childhood sensorineural deafness and 2% of congenital heart defects were attributed to
congenital rubella infection in both the United States and the United Kingdom. During the epidemic of
1962 to 1965, rubella infections during pregnancy were estimated to have caused 30,000 stillbirths and
20,000 malformed infants in the United States. The US rubella vaccination program, which calls for
vaccination of all children, has significantly reduced the incidence of rubella. Cytomegalovirus (CMV):
CMV is a significant cause of morbidity and mortality, especially in organ transplant recipients and
individuals with AIDS.(1,2) CMV is also responsible for congenital disease of the newborn. Infections
with CMV result from reactivation of latent virus from a previous infection, transmission of the virus
from a donor organ or blood product, or initial or primary contact with the virus in a seronegative
patient. Infection in immunologically normal patients can cause mononucleosis similar to that produced
by infection with Epstein-Barr virus (EBV). Infection in immunocompromised hosts commonly results
in more severe disease. Herpes Simplex Virus (HSV): The herpes virus family contains HSV types 1
and 2, varicella-zoster virus, CMV, EBV, and human herpesvirus 6, 7, and 8 (Kaposi sarcoma). HSV
types 1 and 2 produce infections that are expressed in various clinical manifestations, ranging from mild
stomatitis to disseminated and fatal disease. The more common clinical conditions include
gingivostomatitis, keratitis, encephalitis, vesicular skin eruptions, aseptic meningitis, neonatal herpes,
genital tract infections, and disseminated primary infection. Infections with HSV types 1 and 2 can
differ significantly in their clinical manifestations and severity. HSV type 2 is the cause of the majority
of urogenital infections and is almost exclusively found in adults. Type 1 HSV is associated closely
with orolabial infection, although genital infection with this virus can be common in some populations.
Useful For: Determination of rubella immune status in individuals >6 months of age As an indication
of past or recent infection with Toxoplasma gondii, cytomegalovirus, or herpes simplex virus in
individuals >6 months of age
Interpretation: Toxoplasma: Diagnosis of acute central nervous system, intrauterine, or congenital
toxoplasmosis is difficult by routine serological methods. A single positive IgG result is only indicative of
recent or previous infection and is present in up to 70% of the adult population in the United States. The
absence of IgG is helpful in that it usually indicates the absence of infection. However, a negative result
could mean either no previous exposure or could also be seen in cases of remote exposure with
subsequent loss of detectable antibody. Seroconversion from negative to positive IgG is indicative of
recent Toxoplasma gondii infection. Seroconversion indicates infection subsequent to the first negative
specimen. Specimens interpreted as equivocal may contain very low levels of IgG. A second specimen
should be drawn and tested. Rubella: By early adulthood, approximately 80% to 90% of the population of
the United States show serologic evidence of having experienced rubella diseases. Rubella vaccine is
recommended for all children, many adolescents, and some adults (particularly females) unless it is
specifically contraindicated. These facts indicate that the expected number of negative rubella serologies
will be very low. A positive result indicates prior immunization or exposure to the virus and immunity
against rubella. Seroconversion indicates infection subsequent to the first negative specimen.
Cytomegalovirus (CMV): Individuals with negative CMV IgG results are presumed to have not
experienced infection with CMV and, therefore, are susceptible to primary infection. A single positive
CMV IgG result indicates past or current CMV infection. Such individuals are potentially at risk of
transmitting CMV infection through blood products; the likelihood of transmission by other modes is not
known. Seroconversion, determined by parallel testing of acute and convalescent phase specimens, is
required to determine whether the infection is a current active infection or a past exposure. A ratio of > or
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