[An outbreak of legionellosis in a nursery]

We experienced an outbreak of legionellosis in infants for the first time in Japan. In Fukushima Prefecture Wakamatsu Nursery, the patients who had respiratory symptoms of cough, wheeze and fever appeared one after another from the middle of June, 2002. We suspected that an outbreak of legionellosis had occurred and then carried out urinary antigen detection of Legionella pneumophila. As a result, 8 patients were positive. They consisted of 5 boys and 3 girls, and ranged in age from 11 months to 1 year 10 months. Underlying disease was observed in one patient, and 6 patients were hospitalized. All 8 patients had rhinorrhea, cough, fever and 7 patients had wheeze. The average duration of cough was 9.9 days and that of fever was 4.5 days. In the admitted 6 patients, WBC ranged in count from 7,500/microliter to 15,300/microliter and CRP ranged from 0.2 mg/dl to 2.5 mg/dl. Chest X-rays showed infiltrative shadows (right lower lobe, left lower lobe) in 2 patients. With regard to the treatment, macrolide or tetracycline antibiotics were administered in 4 of 8 patients, and beta-lactams were administered in others. Water samples were obtained from 12 locations at the nursery, including the shower head of the bathroom, the bathtub, the taps, the laundry and so on. But cultures of water samples failed to grow legionella. We suspected that the source of infection was the humidifiers or the nebulizer used for disinfection. Through this outbreak, it became obvious that the mild case of legionellosis really existed. Furthermore, we suggested that it was possible for the patient with mild legionellosis to cure without administration of macrolide or tetracycline antibiotics.