The present invention relates to the use of the antiviral activity of exogenous leukotriene B.sub.4 (LTB.sub.4), variants and derivatives thereof as a therapeutic agent in viral infections caused by human and animal enveloped RNA viruses. The human and animal enveloped RNA viruses are RNA viruses, such as togaviridae, orthomyxoviridae, paramyxoviridae, coronaviridae, filoviridae, arenaviridae, bunyaviridae, rhabdoviridae and flaviviridae in general, and Retroviridae such as HIV-1 and HIV-2.