The virus is basically the same the world-over.

In fact one of the positive things about it, in terms of working on a possible vaccine, is that it shows very few & minor mutations wherever it's been tested (unlike common 'flu strains). This is thought to be because of its virulence, if it wasn't more virulent then we would probably see more mutation.

The reason that some otherwise healthy people succumb to the virus, is due to viral load - nothing to do with Johnson not being present at COBRA meetings or what this government has or has not done. If you expose anyone to a high-enough level of viral organisms, or expose them frequently to these organisms, then the viral population in effect overwhelms the immune response. This is what we see in healthcare workers.

If you put someone in an environment where lots of people (or things) around them are infected, or they are coming into close contact with someone (or something) with the virus frequently, then their viral load increases - nothing to do with Johnson not being present at COBRA meetings or what this government has or has not done. That's why distancing & hygiene are so important.

Viral load is person-specific. It doesn't spread. Someone with a higher-viral load doesn't shed the virus at a greater rate again nothing to do with Johnson not being present at COBRA meetings or what this government has or has not done.

The reason why isolating yourself is important if you're infected, is as much to keep yourself safe, as to avoid passing it on to others.