Measles, Mumps, and Rubella - Centers for Disease Control and ...

Vol. 47 / No. RR-8 MMWR 43Cases meeting the measles case definition are excluded, as are cases with serologicfindings compatible with recent measles virus infection.A probable case of rubella• meets the clinical case definition for rubella, and• has no or noncontributory serologic or virologic testing, and• is not epidemiologically linked to a laboratory-confirmed case.A confirmed rubella case• meets the laboratory criteria for rubella, or• meets the clinical case definition and is epidemiologically linked to a laboratoryconfirmed case.Suspected and known rubella cases should be reported immediately to local healthdepartments. Aggressive case finding and intensified surveillance for CRS should follow.Rubella surveillance is complicated by the nonspecific nature of the symptoms ofthe clinical disease. Rubella can be confused with other illnesses, including measles.Thus, all rubella cases, particularly isolated cases that do not occur as part of an outbreak,should be confirmed by laboratory testing. Confirmed rubella cases arereported to the CDC by state health departments. Cases of febrile rash illness that arelaboratory-negative for rubella may be measles (rubeola) and the patients should betested for measles IgM.Laboratory confirmation of suspected cases of CRS also is necessary because theconstellation of findings of CRS varies. Case reports of indigenous congenital rubellasyndrome are sentinel events, indicating the presence of rubella infections in the communitythat may previously have been unrecognized. The diagnosis of one or moreindigenous CRS cases in a community should trigger intensified rubella and CRS surveillance.A confirmed case of CRS has laboratory confirmation of rubella infection andat least one defect in each of the two following categories: a) cataracts/congenitalglaucoma (either or both count as one), congenital heart disease, loss of hearing, pigmentaryretinopathy; and, b) purpura, splenomegaly, jaundice, microcephaly, mentalretardation, meningoencephalitis, radiolucent bone disease.A probable case of CRS has any two conditions listed in category a) or one fromcategory a) and one from category b) and lacks evidence of any other etiology. A casewith laboratory evidence of rubella infection but no clinical symptoms or signs of CRSis classified “infection only.”Laboratory DiagnosisThe criteria for laboratory diagnosis of rubella are• a positive serologic test for rubella IgM antibody; or• a significant rise between acute- and convalescent-phase titers in serum rubellaIgG antibody level by any standard serologic assay; or• the isolation of rubella virus from an appropriately collected clinical specimen.