Influenza A in immunocompromised patients.

Immunocompromised patients with influenza A were identified in Stockholm during two influenza seasons. The predominant subtypes were H3N2 during 1988-1989 and H1N1 during 1990-1991. The median age of the 25 patients was 43 years (range, 3-80 years). Twelve patients had received renal transplants and had ongoing immunosuppression. Seven patients had received bone marrow transplants between 2 days and 3 years before becoming infected with influenza virus A. Two patients were in an aplastic phase, and four had chronic graft-versus-host disease with ongoing immunosuppression. Six patients had hematologic malignancies. Two of the 25 patients had severe infections. One of these infections occurred in a bone marrow transplant recipient during an aplastic phase and was fatal; the other affected a patient who had received a renal transplant. One bone marrow transplant patient had mild but protracted infection. The remaining 22 patients had mild influenza A. We conclude that influenza A in immunocompromised patients occasionally causes severe complications but in most patients is mild and self-limiting.