A method of treating viral infection, such as viral infection caused by a virus of the Filoviridae family, Flaviviridae family (Flavivirus genus), Deltaretrovirus genus, or Togaviriade family is provided. A composition having at least one cardiac glycoside is used to treat viral infection. The composition can further include at least one triterpene. Alternatively, the composition comprises at least one, at least two, or at least three triterpenes.