Rubella
Rubella (German measles, 3-day measles) is a highly infectious viral rash illness caused by a togavirus of the genus Rubivirus. It is transmitted in nasopharyngeal secretions of infected individuals via airborne droplets. Incubation period is 14 days with a range of 12-23 days. Rubella is communicable up to 7 days before and 7 days after onset of the rash.
If Rubella is contracted by a woman in her first trimester of pregnancy the virus may affect all organs of the fetus and cause a variety of congenital defects including, but not limited to, fetal death, spontaneous abortion, or premature delivery, deafness cataracts, glaucoma, retinopathy, microphthalmia patent ductus arteriosus, ventricular septal defect, pulmonic stenosis, coarctation and/or neurologic abnormalities. Infants with Congenital Rubella Syndrome shed virus in nasopharyngeal secretions and urine and can shed virus for up to one year.
Adults may experience a 1–5 day prodrome of low-grade fever, headache, malaise, lymphadenopathy, mild coryza, and conjunctivitis. Postauricular occipital and posterior cervical lymphadenopathy is characteristic and precedes the rash by 5-10 days. Rubella is characterized by an erythematous maculopapular rash and Koplik spots. The maculopapular rash begins on the head and moves rapidly to the trunk. It usually does not coalesce. Arthralgia or arthritis may occur in up to 70% of adult women with Rubella.
Complications may include otitis media, bronchopneumonia, laryngotracheitis, diarrhea and thrombocytopenia. Acute encephalitis occurs in approximately 1 in every 1000 cases.
Other viruses can cause a similar rash and symptoms. Serological testing can be helpful in confirming the diagnosis. Serological tests are also useful in determining the immune status of pregnant women. Rubella-specific IgG, IgM, and IgA antibodies develop rapidly after the onset of rash. IgM antibodies are detected within 5 days after the onset of rash and persist for 6 to 12 weeks. In some atypical cases, IgM antibodies may persist for a year. IgG antibodies persist for life.
Reinfection can occur in persons who develop low levels of IgG antibody after natural infection or immunization. In these cases, IgM antibodies are detectable transiently within six weeks of exposure. IgM levels are usually lower than those seen in primary infections.
Vaccination induces an immune response in approximately 95% of vaccinees. IgG antibodies develop 10 to 28 days after vaccination. Antibodies persist for at least 18 years in 90% of individuals. Rubella IgM antibodies can also be detected for 3 to 8 weeks after vaccination.
Results are reported as negative or positive and can be interpreted as follows:
|
IgM |
IgG |
Interpretation |
|
Negative |
Negative |
Seronegative - no evidence of infection |
|
Positive |
Negative |
Active infection |
|
Positive |
Positive |
Recent infection or reactivation |
|
Negative |
Positive |
Past infection or vaccinated |
Rubella-specific immunoglobulin M (IgM) antibody should be drawn at least 3-5 days after the onset of the rash. Specimen requirement is one red top or SST tube of blood.
Virus can be isolated from nasal secretions, blood, throat swab, urine, and cerebrospinal fluid. Virus can be isolated from the pharynx 1 week before and until 2 weeks after rash onset. Viral isolation is an extremely valuable epidemiologic tool, and should be attempted for all suspected cases of Rubella.
