Article in Japanese

A case of invasive meningococcal disease in an infant transmitted by a father with a history of overseas travel

Tomo Sakurai^{1, 2）}, Yuichi Aoki^1）, Haruna Otani^1）, Kota Ao^1）

Invasive meningococcal disease is rare in Japan, with approximately 40 cases reported annually, and outbreaks have occurred have been observed particularly in dormitory settings. Here, we report a case of meningococcal bacteremia in a 7-month-old boy with no history of communal living. He initially presented with fever at a local clinic and was referred to our hospital on the second day of illness. In the absence of respiratory symptoms or epidemiologic evidence of viral infections, occult bacteremia was considered a possible cause. Although the patient remained clinically stable, blood tests revealed elevated inflammatory markers. Occult bacteremia was therefore suspected, and empirical antibiotic therapy was initiated. Neisseria meningitidis strain was isolated from the blood culture, confirming a diagnosis of invasive meningococcal disease. As cerebrospinal fluid analysis revealed no significant findings, treatment was focused on bacteremia. Subsequently, it was discovered that the patient's father had recently traveled to the Philippines, and N. meningitidis strain was isolated from his nasopharynx, suggesting travel-associated transmission. Given the potential severity of this infection, prophylactic antibiotics were administered to the patient’s family members, healthcare workers, and other hospitalized patients to prevent secondary transmission. With the resumption of international travel following the COVID-19 pandemic, this case highlights the importance of assessing travel history in febrile patients, even in the absence of known local outbreaks.

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1）Department of Pediatrics, Yamato Municipal Hospital
2）Department of Pediatrics, NHO Yokohama Medical Center

Key words	invasive meningococcal disease, travel-associated transmission, family transmission, bacteremia
Received	July 16, 2025
Accepted	February 12, 2026

38 (2)：131─136,2026