What makes some viruses more infectious than others? This week a new strain of the SARS-CoV-2 virus was discovered in the UK, and reports are saying that it's more infectious than the strains we've been dealing with for the past year. Which made me wonder: what is it about different strains (or different viruses in general) that makes them more of less infectious than others? They've been saying that they don't think the new strain will be any more resistant to the vaccines. Does that mean they're no more able to evade the immune system? Or is it just the immune system that hasn't been primed by a vaccine?

To name a few parameters that can determine the infectiousness of a pathogen:

* Transmission pathways used (aerosols, surfaces, vector organisms, feces etc.)
* Molecular affinity to bind to host cell (how well does it penetrate the cell)
* Strategy within host cell (lysogeny, lysis)
* Interaction with the host’s immune system