Methods of using viruses labeled with alkyne-modified biomolecules, such as fatty acids, carbohydrates and lipids, to treat a plant, an insect or an animal infected with a virus or to increase the infectivity of a virus, such as the human immunodeficiency virus, are provided. Also provided are methods of labeling a virus, such as human immunodeficiency virus, with an alkyne-modified biomolecule, such as a fatty acid, a carbohydrate, or an isoprenoid lipid. The viruses labeled with alkyne-modified biomolecules may be combined with a pharmaceutically acceptable excipient to produce a pharmaceutical composition, optionally containing another anti-viral agent and/or a delivery agent, such as a liposome.