Olive Lead Extract Olive leaf extract is an herbal supplement that has been shown to be effective  against virtually all the viruses and bacteria on  which it has been tested. Laboratory studies suggest that olive leaf extract interferes with viral infection becoming established and/or spreading either by rendering viruses incapable of infecting cells or by preventing them from reproducing. It has been shown to help protect against infection by such viruses as human immunodeficiency virus (HIV),  herpes viruses, and influenza viruses. It is useful for such disorders as pneumonia, sore throat, sinusitis and skin diseases such as chronic infections and rashes, as well as fungal and bacterial infections.