Viruses are kind of mysterious – there is debate on whether on not they are “alive”. At a basic level, viruses are proteins and genetic material that survive and replicate within their environment, inside another life form. In the absence of their host, viruses are unable to replicate and many are unable to survive for long outside the host. Therefore, if they cannot survive independently, can they be defined as being ‘alive’? Taking opposing views, two microbiologists discuss how viruses fit with the concept of being ‘alive’ and how they should be defined.