We found that several solid-state cuprous compounds, including cuprous oxide (Cu2O), sulfide (Cu2S), iodide (Cul), and chloride (CuCl), have highly efficient antiviral activities, whereas those of solid-state silver and cupric compounds are markedly lower. On a Cu2O-loaded glass substrate, for example, the infectious activity of bacteriophages was reduced by 5-orders of magnitude within 30 min and by 3-orders of magnitude within 1 h for bacteria. In contrast, the infectious activities of both phages and bacteria were not markedly reduced on CuO-loaded substrates within a similar time frame. To determine the origin of this inhibitory activity, we investigated the effects of reactive oxygen species (ROS), leached copper ions, and the solid-state compound itself against bacteriophages, and concluded that infectious activity is lost following direct contact with the solid-state surface of cuprous compounds, but not ROS or copper ions. Furthermore, we found that Cu2O adsorbed and denatured more proteins than CuO, which suggests the difference of the inhibitory activity between Cu2O and CuO. (C) 2012 Elsevier B.V. All rights reserved.