ERVW-1 and viral infectious disease: The H. sibthorpioides extracts might interrupt the interaction of several envelope glycoproteins with cell surface receptors requires for fusion of the virion envelope with a cell plasma membrane [13], resulting in ineffective viral infection. H. sibthorpioides extracts presented low to mild prophylactic effects on C6/36 and Vero cells, perhaps due to the presence of various plant alkaloids in the crude extract of H. sibthorpioides, which may act synergistically to decrease the effective interaction of the active compounds.