Can the Definitions of SARS-Cov-2 and Covid-19 Stand Up to Epistemological Scrutiny?

The understanding and handling of what is known as the Covid-19 pandemic is based on the validity and legitimacy of genomic epidemiology with its taxonomies that include the immense SARS-Cov-2 corona subclass of genomic sequences. For a taxonomy based on genomic sequences to be pertinent to genomic _epidemiology_ (as opposed to genomics _tout court_), its classes of sequences would have to correspond clearly to epidemiological data; and yet there is no such correspondence. The reduction of epidemiology (macro-biology) to genomics (nano-biology) is far from trivial and cannot simply be taken for granted. Against this background, we argue that the definitions of SARS-Cov-2 and Covid-19 do not stand up to epistemological scrutiny: these definitions do not hook on to a new natural kind that is pertinent for epidemiology.