in·fect / inˈfekt/ • v. [tr.] affect (a person, organism, cell, etc.) with a disease-causing organism: there is no evidence that the virus can infect humans. ∎ contaminate (air, water, etc.) with harmful organisms. ∎ Comput. affect with a virus. ∎ fig. (of a negative feeling or idea) take hold of or be communicated to (someone): the panic in his voice infected her.DERIVATIVES: in·fec·tor / -ˈfektər/ n.