Prolonged shedding of amantadine-resistant influenzae A viruses by immunodeficient patients: detection by polymerase chain reaction-restriction analysis.

Consecutive A (H3N2) influenza virus isolates from 2 influenza virus-infected immunodeficient patients treated with amantadine were examined using a novel polymerase chain reaction (PCR)-restriction analysis for resistance to this antiviral compound. The data indicate that immunodeficient patients may shed resistant viruses for prolonged periods and with different drug resistance mutations present at different times. This PCR-restriction technique allows rapid detection of amantadine- or rimantadine-resistant strains.