Prevention of traveler's diarrhea: a call to reconvene.

5.5-fold increase in antimumps IgG antibody concentration to 16,000 IU/mL. The third case occurred in a 30-yearold male pediatric resident with no history of mumps vaccination who had mumps disease during childhood. He had an antimumps IgG antibody concentration of 33 IU/mL in a serum sample obtained for screening for newly employed health care workers at our institution. One year later, the patient developed acute bilateral parotid swelling. Examination of a serum sample obtained at that time revealed an 8.5-fold increase in IgG antibody concentration to 277 IU/mL; this sample was tested together with the previous sample and was antimumps IgM antibody negative. Neutralizing assays confirmed reinfection, despite pre-existing neutralizing antimumps serum antibodies. Ten days later, the patient’s 26-year-old female partner (with no history of mumps disease or vaccination) developed a primary mumps infection (IgM antibody positive). These cases illustrate that symptomatic mumps reinfection may occur in the presence of pre-existing specific mumps virus serum antibodies.