LAUSR

Background Extended use of oseltamivir in an immunocompromised host could reportedly induce neuraminidase gene mutation possibly leading to oseltamivir-resistant influenza A/H3N2 virus. To our knowledge, no report is available on the clinical course of a severely immunocompromised patient with a dual E119D/R292K neuraminidase mutated-influenza A/H3N2 during the administration of peramivir. Case presentation A 49-year-old male patient was admitted for second allogeneic hematopoietic cell transplantation for active acute leukemia. The patient received 5 mg prednisolone and 75 mg cyclosporine and had severe lymphopenia (70/μL). At the time of hospitalization, the patient was diagnosed with upper tract influenza A virus infection, and oseltamivir treatment was initiated immediately. However, the patient was intolerant to oseltamivir. The following day, treatment was changed to peramivir. Despite a total period of neuraminidase-inhibitor administration of 16 days, the symptoms and viral shedding continued. Changing to baloxavir marboxil resolved the symptoms, and the influenza diagnostic test became negative. Subsequently, sequence analysis of the nasopharyngeal specimen revealed the dual E119D/R292K neuraminidase mutant influenza A/H3N2. Conclusions In a highly immunocompromised host, clinicians should take care when peramivir is used for extended periods to treat influenza virus A/H3N2 infection as this could potentially leading to a dual E119D/R292K substitution in neuraminidase protein. Baloxavir marboxil may be one of the agents that can be used to treat this type of mutated influenza virus infection.