Subacute Sclerosing Panencephalitis: More Cases of This Fatal Disease Are Prevented by Measles Immunization than Was Previously Recognized

Background. The most severe sequela of measles virus infection is subacute sclerosing panencephalitis (SSPE), a fatal disease of the central nervous system that generally develops 7-10 years after infection. From 1989 through 1991, a resurgence of measles occurred in the United States, with 55,622 cases of measles reported. The purpose of the present study was to identify cases of SSPE that were associated with the resurgence of measles and to calculate the risk of developing SSPE. Methods. Brain tissue samples obtained from 11 patients with a presumptive diagnosis of SSPE were tested for the presence of measles virus RNA. Measles virus genotypes were determined by reverse-transcriptionpolymerase chain reaction (RT-PCR) and by analysis of the sequences of the PCR products. A search of the literature was conducted to identify reports of cases of SSPE in persons residing in the United States who had measles during 1989-1991. Results. The measles virus sequences derived from brain tissue samples obtained from 11 patients with SSPE confirmed the diagnosis of SSPE. For 5 of the 11 patients with SSPE who had samples tested by RT-PCR and for 7 patients with SSPE who were identified in published case reports, it was determined that the development of SSPE was associated with the measles resurgence that occurred in the United States during 1989-1991. The estimated risk of developing SSPE was 10-fold higher than the previous estimate reported for the United States in 1982. Conclusions. Vaccination against measles prevents more cases of SSPE than was originally estimated.