A quantifiable phenotype of viral propagation.

A system has been identified where a virus, replicating continuously on its host, displays a distinct and quantifiable phenotype, and thereby continuously reports on the state of the virus-host relationship. When bacteriophage T7 is plated out with its host, Escherichia coli, it establishes a constant-velocity infection wave, which is driven by an autocatalytic reaction-diffusion mechanism. The velocity--which is easily measured--continuously reflects the infection environment. The simplicity of the system extends to the investigator an unprecedented ability to monitor and control a viral infection process.