Clinical management and viral genomic diversity analysis of a child's influenza A(H1N1)pdm09 infection in the context of a severe combined immunodeficiency.

INTRODUCTION: A child with severe combined immunodeficiency (SCID) had an influenza A(H1N1)pdm09 infection with viral excretion longer than 6 months, during 2013-2014 influenza season, despite cord blood transplantation and antiviral treatments.

METHODS: Conventional real-time RT-PCR methods were used to estimate viral load and to detect the presence of the common N1 neuraminidase (NA) H275Y substitution responsible for oseltamivir resistance. Next-generation sequencing (NGS) of influenza viruses was performed retrospectively to characterize viral quasispecies in specimens.

RESULTS: The patient was first treated with oral oseltamivir, leading to detection of low-levels of NA-H275Y substitution. Concomitant cord blood cell transplantation, intravenous administration of zanamivir and immunoglobulins led to an increase in white blood cells and influenza viral load decrease. A viral rebound occurred as soon as the antiviral treatment was discontinued. Eventually, influenza viral load was negated with immune reconstitution. NGS found influenza quasispecies harboring NA-E119A substitution (10.3%). Moreover, NGS showed that viral genomic diversity evolved under antiviral treatment and immune status.

CONCLUSIONS: Conventional virological techniques were sufficient for influenza infection follow-up but NGS performances allowed characterization of viral variants evolution in this specific case of prolonged influenza virus infection. New and efficient treatments against influenza in immunocompromised patients are needed.