Are viruses alive?

Viruses are not considered living organisms by most virologists. Virology Blog lists four criteria necessary for a definition of life: metabolism, growth, reproduction and an ability to react to external stimuli.

According to Virology Blog, viruses fail to meet three of the four criteria of living organisms. Though they are capable of reproduction, viruses have no metabolic machinery of their own. They also tend not to grow, as they emerge from their host cell fully developed. What interactions viruses have with their surrounding environment takes place on the level of molecular chemistry, and it does not strictly meet the established definition of stimulus response.