If you would compute the mass of a typical infection dose or even a full-blown infection and calculated the maximum caloric content in all the chemical bonds, I

If you would compute the mass of a typical infection dose or even a full-blown infection and calculated the maximum caloric content in all the chemical bonds, I'm pretty sure it would amount to not much more than a grain of rice or similar. It is conceivable and probable that some parts of viruses get broken down to keto bodies usable in the krebs cycle. The amino acids in the capsule for sure. Parts of the lipids of a viral membrane (which some virus have) maybe. But those aren't special mechanism and are used more as an accident to the destruction of viral particles rather than an intentional harvesting of energy. The energy expended to destroy the particles in the first part is also probably greater.