Embodiments of the present invention relate generally the use of certain compositions, e.g., compositions comprising a glutathione precursor and a selenium source, in the therapy of viral diseases and/or reducing the incidence of viral diseases. Related embodiments of the present invention relate to treatment and/or reducing the incidence of respiratory ailments caused by respiratory syncytial virus (RSV) or hemorrhagic fever (EHF) caused by Ebola viruses (EBV) or Marburg virus. Yet in other embodiments, the invention relates to reducing metal toxicity in a biological system, which involves contacting the biological system with a composition comprising a glutathione precursor and a selenium source, optionally together with a chelating agent, an antioxidant, a metallothioneine protein or a fragment of metallothioneine.
