We report herein the clinical symptoms and laboratory findings of 22 rubella patients, 20 males and 2 females, seen at our hospital from December 20, 2012, to February 4, 2013. The ages of the male subjects ranged from 20 to 44 years old, while those of the female subjects ranged from 24 to 35 years old. All the patients had fevers, with 8 patients (36%) having a fever of 38 degrees or higher. An erythematous maculopapular rash was observed in all of the patients, and a fusion rash appeared in 20 patients (91%). Postauricular and submandibular lymphadenopathy was observed in 19 patients (86%), and conjunctival hyperemia in all of them. These adult cases of rubella were noted to be more severe than the pediatric cases. All of the patients were found to be positive for the rubella IgM antibody. Seven patients were negative on the first visit but were positive by the next visit. Rubella patients are unlikely to test positive for the antibody in the early stages of infection. We presumed that the rubella IgM antibody level would become elevated approximately on day 3. From detailed interviews, we determined that 14 of the patients had gone to pachinko parlor A within 2–3 weeks before the onset of rubella. We hypothesized that rubella had spread within the store, which was a closed space. Because of the history of vaccination in Japan, those who are now between the ages of 26 and 34 are likely to have low immunization coverage, as in our cases. Rubella is currently prevalent in the Tokyo metropolitan area and the Kansai region. The recent increase in the number of reported infections is a matter of grave concern.
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