Abstract: Methods of treatment of the human or animal body are provided to combat conditions responsive to lithium and/or C.sub.18-22 polyunsaturated fatty acid therapy, including conditions associated with essential lithium deficiency, and also transfer of lipid-enveloped viruses between humans or animals or between cells within a human or animal body. The methods include administration of an effective amount of a lithium salt of a C.sub.18-22 polyunsaturated fatty acid. Devices for combatting transmission of viral diseases including lithium salts of a C.sub.18-22 polyunsaturated fatty acid are also provided.