Emergence and Apparent Transmission of Rimantadine-Resistant Influenza A Virus in Families

Abstract To determine whether rimantadine can protect family members from acquiring influenza A viral illness and to assess the possible selection of drug-resistant strains of virus, we conducted a randomized, double-blind, placebo-controlled study in three communities during two influenza seasons. When influenza A occurred in a family, the members (including the index patient) were given either rimantadine (adult oral dose, 200 mg per day) or placebo for 10 days. The presence of illness was monitored by daily recording of symptoms and temperature measurements; infection was determined by isolation of the virus and by serologic studies. Among households with documented influenza A infections, symptomatic illness occurred in one or more contacts in 10 of 28 families treated with rimantadine and in 10 of 29 families treated with placebo. Asymptomatic secondary influenza A infections were found in five families assigned to receive rimantadine and in four families assigned to receive placebo. Rimantadine-resi...