Faviparivir antiviral drug, molecular model. Also known as T-705, Avigan, or favilavir, this is an antiviral drug with activity against many RNA viruses, and is being used in tests to treat the novel coronavirus (SARS-CoV-2). This coronavirus causes a respiratory infection (Covid-19) that can lead to fatal pneumonia. As of March 2020, the virus has spread to many countries worldwide and has been declared a pandemic. Over 200,000 have been infected with several thousand deaths. This antiviral drug is a pyrazinecarboxamide derivative. The chemical formula is C5.H4.F.N3.O2. Atoms are represented as colour-coded spheres: hydrogen (grey, small), carbon (grey, large), oxygen (red), nitrogen (blue), fluorine (green).