Disclosed are compounds and pharmaceutical compositions containing compounds that inhibit JMJD2 proteins, including those of the formula (I) : wherein R1, R2, R3, R4, and R5 are as defined herein or pharmaceutically acceptable salts thereof. Also disclosed is a method of preventing or treating a viral infection of a host, comprising administering to the host an effective amount of an inhibitor of the JMJD2 family of histone demethylases, for example, a compound of the formula (I). The viral infection may be a primary infection, reactivation of a virus after latency in a host, or may be in a mammal that has undergone, is undergoing, or will undergo immunosuppressive therapy.