Seven cases of mumps were reported during 2000, compared with one case in 1999 and 13 cases in 1998. The seven cases included three children ages 6, 11, and 13 years and four adults ages 25, 34, 42, and 44 years. The 6- and 13-year-old both had a history of two doses of age-appropriate MMR vaccine, and the 11-year-old had a history of one dose of MMR vaccine. None of the adults had a known history of MMR vaccine. None of the cases had a history of travel, and there was no evidence of secondary transmission.
The cases reported in 2000 all were laboratory-confirmed by positive IgM serology; however, none had acute and convalescent serum results available to demonstrate a rise in serum IgG antibody. Although a positive serologic test for mumps IgM antibody is considered laboratory confirmation, false-positive IFA tests for mumps IgM have been reported. Therefore, it is recommended that both IgM and IgG serologic testing for mumps should be performed for all sporadic cases of mumps. Blood specimens for acute and convalescent serum IgG should be drawn as soon as possible after onset of swelling and 3 to 5 weeks later; tests should be run as paired sera. Confirmed cases of mumps also should meet the clinical case definition (i.e., acute onset or unilateral or bilateral tender swelling of the parotid or other salivary gland lasting >2 days).
The mumps cases reported in 2000 highlight the need to assess mumps immunization status of adults and to implement current recommendations for mumps vaccine for adults born in 1957 or later.